# Killed the MS880 while milling



## Kicker_92

Got the bar pinched in the middle of a slab and must've gotted a bit too hot, and it died. Trying to start it afterward revealed very little compression. :censored:

It melted off a corner of the piston. This also galled up the cylinder head, which might be salvagable with some honing, but the piston is toast.I tried to sand off some of the slag, but the ring grooves are soo tight that the rings are stuck inside.

I'm thinking the mixture must've been a bit lean, the plug was brown, but a very light shade of brown. It'd been running really nice up until then too, but looks like our milling might be on hold for a bit. 

Any suggestions? :help:


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## stihlboy

sounds like you are in the market for another saw......

p&c is about $350 plus install....


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## LoggN

Thats harsh, bit to lean looks to be a factor. Maybe you know but never run the saw dry out of fuel, I hear the quality of our pump gas is garbage! Kinda like this ultra low sulpher diesel they pump into us to ruin our older diesel trucks. Just a thought.


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## DRB

So sad 

I don't think the cylinder can be saved? 

Hope you find a reasonable way to get fixed up a new 880 is not cheap.


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## chuckwood

*looks exactly like a Husky 350 I'm fixing*



DRB said:


> So sad
> 
> I don't think the cylinder can be saved?
> Hope you find a reasonable way to get fixed up a new 880 is not cheap.



The photos of the piston and cylinder look exactly like what I saw when I examined a Husky 350 someone gave me. I read all the threads about restoring cylinders, and started working on mine with muriatic acid, also used oven cleaner. With a bit of work and wet sanding with 400 grit, I removed the smeared on aluminum and got the bore smoothed out. The nikasil coating is so tough that maybe it can withstand a beating like that from a melting piston. I've got a cheap 30 dollar aftermarket piston coming via ebay, and in a week or so, I'll find out if my first rebuild is gonna work. Don't really need the 350, got too many saws as it is, but it was free and I just want the experience of doing it and to see what happens. 

It may be that the 880 can be revived with a bit of chemicals and sanding, but with an expensive saw like that, a cheap aftermarket ebay piston may not be a good idea.


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## BobL

In analysing the circumstance I'd be asking myself the following
How does a bar get pinched when milling?
What type of wood were you cutting?
How long had it been since the chain was sharpened?
What fuel/lube mix are you running?
How many RPM below max have you got the H screw set at ?
How much pushing was happening?

Fear of this is what leads me to this.





I reckon your cylinder is salvageable.


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## BlueRider

In addition to the questions Bob asked I would also want to know what kind of bar oil you are running and if you are using a roller/sprocket nose bar and the lenght of the bar. Of course the piston siezing may have just made it seem like the bar was being pinched.

Your toasted p&c is exactly why I like the older saws over the new ones, specificaly the 075/076 as their design puts the exhaust away from the log where it bounces back into the saw. Bob has addresed this problem with his awsome exhaust pipe mod. I think Bobs clutch cover mod may also lower the running temp due to the decreased heat from a clutch being run clogged full of sawdust. I am a bit on the fence on this mod due to removing the cluth cover also removes a bit of the thermal heat sink that helps cool the saw. 

If that is a head temp guage on Bob's saw that is also a great mod and would tell the truth about the effectivness of any future mods. I was just thinking about how to add an on board tack and temp guage as well as extended H and L screws for on the fly tuning.


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## huskyhank

Sorry for your troubles.

The rev limit on my 3120 is looking better after seeing this. But I sure wish it had a high speed screw. Keeping the saw on a very slight blubber under load will help prevent this.


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## Andrew96

Being an 'engine guy' and having raced..burned, broke many a 2 stroke motorcycle over the years...it's very easy to see what happened to your saw...even without getting a lope out and having a real look. Immediately I see two signs. Signs of detonation (preignition). Yes...very hard to tell on a 2 stroke until it fails if you cannot 'read' a plug properly with todays fuels. However...look at the photo up the cylinder. See the funny burn pattern? Less carbon in the intake side (cooler)..thats good, more on the exhaust side still OK....but look a bit closer...see the specs..the specs where the carbon is missing...the dot like marks. You ran this hot, and fast..but this was preignition that overheated the assembly and overheated (burned) the piston edge. There was more heat in that cylinder than you could cool off due to the ping. Look again at your piston photo. I know you took the photo to show a melted piston onto the rings..but look at the combusion pattern on the top..get your magnifying glass out..that's the key..that's what you should be looking at. On the exhaust side (of course..that's where the heat is), you can see the speckling again. Detonation has broken off the carbon deposits on your piston crown. The problem is..this 'just didn't happen' IMO. Sorry to tell you but look at the missing piston edge. Where did it go? It certainly isn't down the piston skirt. It's been burning off for awhile. Ping by ping. This should have shown up on your spark plug (don't just look at the colour...look for zits on it...speckles of carbon looking stuff..which is actually aluminum). As for a failure mode..well preignition for sure. I don't think getting the saw stuck (still don't know how) had much to do with it..other than some extra heat. This has been on a route to failure for awhile...at least for the last 10 - 20 minutes or so. 
I think you'll be able to save that cylinder (if you're careful with the acid). I'd pull the crank and make sure there isn't anything, other metal debris down there. I'd then be checking your ignition timing. If that's fine and hasn't moved..then your fuel has water in it, is of too low an octane for your compression, or location, or (though I don't think so..without looking at your assembly under magnification) you just plane ran it too lean (lean doesn't usually = preignition though). Too much timing, or low octane like water or wrong gas, old gas. 
Just my thoughts. I've only seen insides of various engines that look like this oh....say 250 times.....

Just looking at your photos again...did you run the proper amount of oil in your fuel? It's hard to tell from the photo but it looks like you have some galling on the piston pin? That's very hard to do...but could just be dirt from your fingers...or some other mark. 
Kind of a lot of blow by for such a low compression engine. Are you sure this didn't have tons of hours on it..coupled with some preignition? 
When you get it together....put a lope in your tool box to look at your spark plug (check for acne on the ceramic bit, electrodes). 

Here's a new rule for you....If you're ever running an engine and all of a sudden it just decided to run really really great...remember to enjoy it since it's just about to fly apart. After a few failures you'll remember to shut it down pull the plug, get the lope out to read the plug.


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## huskyhank

I think Andrew96 has hit the nail on the head.


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## BlueRidgeMark

:agree2:


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## Kicker_92

Andrew96 said:


> The problem is..this 'just didn't happen' IMO. Too much timing, or low octane like water or wrong gas, old gas.
> 
> Just looking at your photos again...did you run the proper amount of oil in your fuel?
> 
> Are you sure this didn't have tons of hours on it..coupled with some preignition?



Thanks for all the great info! Your probably right that this was just a coincidence with getting stopped mid cut. The wedges in the cut slipped, the chain cut a groove and free revved for 4-5 seconds.

- We mix with stihl oil, and run at 40:1. Perhaps we should go with a little might oil, say 35:1?

- The engine did have a lot of hours on it to start with, and I've put on around 80 hours of milling time. When I say it's been running great lately, I meant for the last 10 hours or so. Had put in a new plug and washed out the air filter really well.

- Chain is sharp, fuel is about half full, and lots of bar oil. Not a lot of resistance in a 20" wide cut, but with the low rakers (8°) it wasn't screaming.

- I'm using 89 octane fuel, no more than 1 month old. We don't have any options here other than ethanol blends, so I try to not keep it around too long.


I'll try cleaning up the cylinder and hone it. If it comes up well then a piston & rings should do it...


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## chuckwood

*honing?*



Kicker_92 said:


> - We mix with stihl oil, and run at 40:1. Perhaps we should go with a little might oil, say 35:1?
> 
> - I'm using 89 octane fuel, no more than 1 month old. We don't have any options here other than ethanol blends, so I try to not keep it around too long.
> 
> I'll try cleaning up the cylinder and hone it. If it comes up well then a piston & rings should do it...



I'm a bit paranoid and run around 30:1, no problems so far, however I do check for soot and carbon buildup from time to time. 

I'm also paranoid with the 89 octane, and I mix 93 and 89 together to get something like 91 octane. 

There's lots of threads and discussion on AS about repairing cylinders. What I've read, and what I've done, is to wet sand with 400 or 600 grit black wet sandpaper, the expensive stuff. I believe if you use anything more like a cylinder hone attached to a drill you risk breaking through the nikasil coating and ruining the cylinder. There's a thread about this right now on the chainsaw forum, a guy had a Stihl shop hone his cylinder, and they cut through the plating. There are photos with the post and you can see the contrast between the aluminum and the nikasil. I've found that hand powered honing isn't much fun and can take quite a while, you must wear heavy and uncomfortable rubber gloves. I used corrosive chemicals as the wet sanding agent, it seemed to work pretty well. I can see the temptation of trying one of those hones with all the little carbide balls attached to them. I've seen them advertised as being useful on 2 stroke motors. Maybe you only use one of those if you plan on having the cylinder replated.


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## mtngun

Andrew96, how does a chainsaw guy know when his saw has pre-ignition problems ? It is easily heard on a 4 stroke, but I've yet to hear pinging on a 2-stroke.

Unless his saw is modded, I doubt if the problem is too much compression or too low octane. 

Correct me if I am wrong, but pre-ignition can be caused by heat -- if a hot spot on the piston or head ignites the fuel -- or by too MUCH squish. Saws rarely have too much squish, so that brings us back to heat.

Aside: my old SBC pings like crazy with only 8:1 compression. The culprit is poor head design with EXCESSIVE squish, typically 0.080"+. The preignition starts in the squish zone. I'm told that tightening squish to 0.040" will greatly reduce preignition.

I don't have your eye for spotting preignition, but what I see has "lean" written all over it. My saw's piston and dome are sooty, and sometimes caked with carbon. Kicker's piston and dome are way too clean.

Kicker, I'd try cleaning the cylinder with acid and maybe skip the sandpaper and hone. You might get by with just a new piston. But figure out why it was lean ! ! !

Sorry about your saw. Thanks for the pics. We'll all learn from your experience.


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## huskyhank

Just my opinion --

Make sure it has the right spark plug. I hope whoever worked on it put the right plug in.

After you put it back together, tune it in a milling cut. Lean it out until it runs fast then back to a very, very slight blubber - maybe even where its just clearing out after being under load for 10-15 seconds. Make a couple of cuts to get it hot and check it again. I'd call it perfect when its blubbery at the start of a cut but clears out after you getting going good. Do not ever run it any leaner than this when milling.


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## SilverBox

mtngun said:


> I don't have your eye for spotting preignition, but what I see has "lean" written all over it.



Yup. I'd vote for too lean myself, when it all goes back together run it PHAT!! . I like to hear a little four stroke in the cut myself, sounds like hell and I'm probably 1k rpm slower then I could safely be, but I know it won't lean seize.


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## spankrz

the standard line for a blown up saw. they bring it in, set it on the counter and say " she run better than she ever did till she quit". lean.


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## rmh3481

How many hours are on the engine? Could there have been an air leak? I would run a pressure test to see if there are any air leaks to know for sure. 
http://www.arboristsite.com/showthread.php?t=112928

Dont use a hone. The plating is .003 thick. Use acid. Acid comes in drain cleaner, oven cleaner, brick cleaner or toilet cleaner. You can use any of these. 

Spread out some newspapers, put the acid in a small glass and use a Qtip. Dab the acid onto the aluminum and allow it to bubble for a minute. Then rinse the acid out of the cylinder with cold water in the sink. Repeat until clean. Acid will not harm the plating. Keep the acid out of the ports and off the combustion chamber. As the aluminum dissolves into the acid, it will turn green.

Order a new piston kit from Baileys; 
http://www.baileysonline.com/itemdetail.asp?item=QS+1124+030+2007&catID=

Fuel the saw with 32:1 mix and set the carb rich for future milling. 

Best wishes,
Bob


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## brncreeper

Andrew96 said:


> Being an 'engine guy' and having raced..burned, broke many a 2 stroke motorcycle over the years...it's very easy to see what happened to your saw...even without getting a lope out and having a real look. Immediately I see two signs. Signs of detonation (preignition). Yes...very hard to tell on a 2 stroke until it fails if you cannot 'read' a plug properly with todays fuels. However...look at the photo up the cylinder. See the funny burn pattern? Less carbon in the intake side (cooler)..thats good, more on the exhaust side still OK....but look a bit closer...see the specs..the specs where the carbon is missing...the dot like marks. You ran this hot, and fast..but this was preignition that overheated the assembly and overheated (burned) the piston edge. There was more heat in that cylinder than you could cool off due to the ping. Look again at your piston photo. I know you took the photo to show a melted piston onto the rings..but look at the combusion pattern on the top..get your magnifying glass out..that's the key..that's what you should be looking at. On the exhaust side (of course..that's where the heat is), you can see the speckling again. Detonation has broken off the carbon deposits on your piston crown. The problem is..this 'just didn't happen' IMO. Sorry to tell you but look at the missing piston edge. Where did it go? It certainly isn't down the piston skirt. It's been burning off for awhile. Ping by ping. This should have shown up on your spark plug (don't just look at the colour...look for zits on it...speckles of carbon looking stuff..which is actually aluminum). As for a failure mode..well preignition for sure. I don't think getting the saw stuck (still don't know how) had much to do with it..other than some extra heat. This has been on a route to failure for awhile...at least for the last 10 - 20 minutes or so.
> I think you'll be able to save that cylinder (if you're careful with the acid). I'd pull the crank and make sure there isn't anything, other metal debris down there. I'd then be checking your ignition timing. If that's fine and hasn't moved..then your fuel has water in it, is of too low an octane for your compression, or location, or (though I don't think so..without looking at your assembly under magnification) you just plane ran it too lean (lean doesn't usually = preignition though). Too much timing, or low octane like water or wrong gas, old gas.
> Just my thoughts. I've only seen insides of various engines that look like this oh....say 250 times.....
> 
> Just looking at your photos again...did you run the proper amount of oil in your fuel? It's hard to tell from the photo but it looks like you have some galling on the piston pin? That's very hard to do...but could just be dirt from your fingers...or some other mark.
> Kind of a lot of blow by for such a low compression engine. Are you sure this didn't have tons of hours on it..coupled with some preignition?
> When you get it together....put a lope in your tool box to look at your spark plug (check for acne on the ceramic bit, electrodes).
> 
> Here's a new rule for you....If you're ever running an engine and all of a sudden it just decided to run really really great...remember to enjoy it since it's just about to fly apart. After a few failures you'll remember to shut it down pull the plug, get the lope out to read the plug.



As Paul Harvey would say: "The rest of the story", great observation and write up!


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## BobL

rmh3481 said:


> Could there have been an air leak? I would run a pressure test to see if there are any air leaks to know for sure.
> http://www.arboristsite.com/showthread.php?t=112928



After reading kickers responses, my money is, it was on the lean side (ie mtngun's comment, Kicker's piston and dome are way too clean) to start with and then the saw developed an air leak.

I'm using 40:1 in much harder wood so it should not be necessary to run 30:1 - at t his ratio many of the additives in the lube are not burned and all it really does is fog the air around the operator with unburnt gunk.


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## Andrew96

mtngun said:


> Andrew96, how does a chainsaw guy know when his saw has pre-ignition problems ? It is easily heard on a 4 stroke, but I've yet to hear pinging on a 2-stroke.



It's very hard to do. I seem to notice when going through a mode whereby you get high cylinder pressures but not high rpms..you can feel/hear it then. Snapping the throttle open when it's just off idle will create nice high cylinder pressures. You might hear it knock now. Way hard to feel or hear than on a 4 stroke since they have a lot of time (more revolutions) to spin down and make a noise. Suffice to say..you look for it with a 2 stroke..feel it/hear it on a 4S. You look for it on the plug under 4x or 10x maginification. Easy to see acne on the plug if you use magnification. Or make sure you give yourself lots of room for problems. Over octane is one way, fresh fuel, avoid enthanol. 



mtngun said:


> Unless his saw is modded, I doubt if the problem is too much compression or too low octane.


 Well I don't think so...he didn't have too much compression..he had too low an octane for that run. 1 month old gas he said...race gas can go 'off' in a day depending on how it was kept. Some guys have gas left in open cans in the sun...that allows some chemicals to flash off into vapour. That affects it's anti knock properties. A can left with the vent open will collect moisture in a few days..ruining it for hard core use. How long did it stay in the gas station? Was that tank full, empty, filled with water to saturation? Lots of things affect the fuels anti knock properties...I mean...he only started off with 89 which around here..is loaded with up to 15% ethanol. That's not going to help. (alcohol holds water, if allowed to absorb it, extra water screws up the anti knock properties of the fuel). There are also 'winter blends' sometimes distributed. Did the station sell him that?




mtngun said:


> Correct me if I am wrong, but pre-ignition can be caused by heat -- if a hot spot on the piston or head ignites the fuel -- or by too MUCH squish. Saws rarely have too much squish, so that brings us back to heat.
> 
> Aside: my old SBC pings like crazy with only 8:1 compression. The culprit is poor head design with EXCESSIVE squish, typically 0.080"+. The preignition starts in the squish zone. I'm told that tightening squish to 0.040" will greatly reduce preignition.
> 
> I don't have your eye for spotting preignition, but what I see has "lean" written all over it. My saw's piston and dome are sooty, and sometimes caked with carbon. Kicker's piston and dome are way too clean.


...yup that's a classic assumption....don't get caught up in it. Clean is not lean...burnt carbon...light coloured is lean (there are more good signs). Look at the colour of the carbon..it's not far off...there just isn't any. Where did the carbon go? It got cleaned off with preignition. Hammered off. Of course, that created extra heat. However, 2 strokes can deal with heat better than some 4s. They eat a lot of heat..then die fast. (the operator would have felt a super hot engine in his hands...or bobl would have popped a barbie lid when he saw his temp gauge numbers), 4s burn valves and run bad before a meltdown (exotic fuels aside). Want to see what his head should have looked like?...look at the side of the piston..the area under the top ring. Lots of blow by...the head should have had more carbon on it than that. Look at the exhaust port..starting to look 'normal' now? Lots of carbon in that assembly..just not in the chamber. 

One of the hardest things I've been doing with engines in the last 15 years..is trying to read plugs/heads burn patterns with the unleaded pump fuels of today. They are hard. I've been reading plugs for a long time and I get stumped many times reading unleaded pump fuel. Harder than you think. Read a head or piston..same signs.

You might see lean....I still see fuel that has the wrong properties. We know he didn't change the compression..we know he didn't put a blower on it, no nitrous. It might have had ethanol in it (which I think should be avoided for non self regulating engines)..it wasn't new fuel, it had a proper mix with good oil. It was a month old, I'll assume a month sitting premixed. I wouldn't completely rule out a vacuum leak but it didn't do a 'lean' meltdown. He just put bad fuel in a 2/3 used up piston.

There is a lot more to a proper fuel mixture than just rich or lean..how much oil. Changing the oil ratio creates a lot of other changes. Running more oil (changing your ratio) to combat high heat so you don't have a meltdown can actually promote running lean (more oil in the fuel means less fuel in your volume). It's not something that you can just twist the needle and richen 'er up a bit..Oil burns at a different speed that fuel (usually slower so it hangs around). Read what the oil manufacturer wants you to mix it at...follow that unless you know 'why' you should change. Prepare to be wrong.


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## Andrew96

rmh3481 said:


> Dont use a hone. The plating is .003 thick. Use acid. Acid comes in drain cleaner, oven cleaner, brick cleaner or toilet cleaner. You can use any of these.
> 
> Spread out some newspapers, put the acid in a small glass and use a Qtip. Dab the acid onto the aluminum and allow it to bubble for a minute. Then rinse the acid out of the cylinder with cold water in the sink. Repeat until clean. Acid will not harm the plating. Keep the acid out of the ports and off the combustion chamber. As the aluminum dissolves into the acid, it will turn green.



Bob...being rather new at playing with stihl saws...I'm not familar with the properties of the plating. However, I doubt you'll find it's 0.003" thick. Maybe that was just a typo. More like 0.0003" thick. However....That's the way to remove the piston flesh from the bore. Qtips, acid and patients. Ha...no hone either...those are for iron bores. Just like you said...unless you are just going to hone it all off and then have to replate. 

The rings are the mating parts here. That beautiful chrome bore you are lucky enough to have for cheap these days..doesn't want to be honed, sanded or otherwise @#$%ed with. Clean it up, new rings on a FORGED piston. Pull the trigger and hang on. 

Sorry for the long posts guys. I've been absorbing info from here for a long time...at least now I'm on familiar ground.


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## Kicker_92

I should probably mention, all my engine experiance is with big V8 4s motors, the 2s repair world is quite new to me.

As far as acid goes, you'd mentioned a couple differant sources, is there a particular acid to look for on the label?

Assuming I can get the cylinder to clean up ok, is there anything else to do while it's apart? On the 4s we'd usually take off any shrap edges or flash that can heat up and cause a preignite, and polish the exaust ports. Does that apply to 2s as well?

Our 89 gas is a 5% ethanol mix. I have the option at some stations of a 94 octane, but that has up to 15% ethanol in it. We'll go down to one gas can instead of two, that should keep it down to a week old max. Would you suggest mixing the oil in right away, or only as we need it? I think the Stihl mix has a stabilizer in it.

Will try the acid & q-tip to clean the aluminum off, just need to know which acid to use.


Thanks for all the help!


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## DRB

Andrew96 said:


> Bob...being rather new at playing with stihl saws...I'm not familar with the properties of the plating. However, I doubt you'll find it's 0.003" thick. Maybe that was just a typo. More like 0.0003" thick. However....That's the way to remove the piston flesh from the bore. Qtips, acid and patients. Ha...no hone either...those are for iron bores. Just like you said...unless you are just going to hone it all off and then have to replate.
> 
> The rings are the mating parts here. That beautiful chrome bore you are lucky enough to have for cheap these days..doesn't want to be honed, sanded or otherwise @#$%ed with. Clean it up, new rings on a FORGED piston. Pull the trigger and hang on.
> 
> Sorry for the long posts guys. I've been absorbing info from here for a long time...at least now I'm on familiar ground.



Not long winded at all.

I have enjoyed your input.


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## huskyhank

Kicker_92 said:


> I should probably mention, all my engine experiance is with big V8 4s motors, the 2s repair world is quite new to me.
> 
> As far as acid goes, you'd mentioned a couple differant sources, is there a particular acid to look for on the label?
> 
> Assuming I can get the cylinder to clean up ok, is there anything else to do while it's apart? On the 4s we'd usually take off any shrap edges or flash that can heat up and cause a preignite, and polish the exaust ports. Does that apply to 2s as well?
> 
> Our 89 gas is a 5% ethanol mix. I have the option at some stations of a 94 octane, but that has up to 15% ethanol in it. We'll go down to one gas can instead of two, that should keep it down to a week old max. Would you suggest mixing the oil in right away, or only as we need it? I think the Stihl mix has a stabilizer in it.
> 
> Will try the acid & q-tip to clean the aluminum off, just need to know which acid to use.
> 
> 
> Thanks for all the help!



I'd keep my gas as fresh as possible and mix just before use. I'd think about how I store my gas. Can that be improved on? Are you sure there are no options for non-ethanol gas where you live? I'd consider aviation gas if I was in a location where non-ethanol fuel is absolutely not available.

But here is the most important part -- I am pretty sure that if you had the high speed screw set just a bit richer you'd still be running your saw. So the main thing is to pay attention to the tune of your saw every time you run it. Check the tune every time you mill. I almost killed my big saw from a small air leak and not paying attention. I want mine blubbering a bit at least at the start of a cut. If its not, I want to know why.


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## WadePatton

op says he_ really cleaned up the air filter_ and the saw ran great between then and failure. if not re-tuned could that be the source of a lean condition? i'm no expert, i'm just asking.

i too am a burble freak.


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## mtngun

You can't trust month old gas ? Get real. In rural areas, people have their own gas tanks which they fill once a year. I use a 55 gallon drum, fill it in the fall, that's my winter supply. Usually there is some left over that I continue to use into summer. Yes, it does soak up water, which settles to the bottom and looks different than healthy gas. The last 5 -10 gallons from the barrel get dumped. Got careless and ended up with some of the watery, one year old gas in my pickup. It didn't like it one bit, but sputtered along. 

I am more careful with gas for saws, though. Try to use fresh ("fresh" can mean several months old, instead of a year old. My "freshest" gas at the moment was purchased in November). 

50:1 is recommended for EPA reasons. Some of the same saws, when sold in Europe, have a 32:1 recommendation. What does that tell you ?

I can believe that there was pinging, as evidenced by the broken piston edge, but it's a chicken or egg question. Did pinging lead to overheating, or did overheating lead to pinging ? I find it easier to believe that the engine was lean, either due to a leak or due to carb tuning, which made the piston too hot, and the hot piston edge acted like a glow plug and caused pre-ignition.

All theory aside, considering the value of an 880, it's worth buying a vac tester and tach to make sure things are right before putting the saw back to work. Check the fuel lines and fuel filter, too, maybe just replace them to be sure.

It's a darn shame about the saw.


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## WadePatton

*i second the vac test notion.*

only 088/880 i've ever seen (purchased new by a woodworker who free-hand slabs with it) has been to the shop twice for air leaks. (which cause lean conditions). i know it was a crank seal at least once.


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## Andrew96

mtngun said:


> You can't trust month old gas ? Get real. In rural areas, people have their own gas tanks which they fill once a year. I use a 55 gallon drum, fill it in the fall, that's my winter supply. Usually there is some left over that I continue to use into summer. Yes, it does soak up water, which settles to the bottom and looks different than healthy gas. The last 5 -10 gallons from the barrel get dumped. Got careless and ended up with some of the watery, one year old gas in my pickup. It didn't like it one bit, but sputtered along.
> 
> I am more careful with gas for saws, though. Try to use fresh ("fresh" can mean several months old, instead of a year old. My "freshest" gas at the moment was purchased in November).



The problem here is your comparing your situation with the OP and I don't think they are the same. I doubt your fresh November gas is stored in a plastic container...no you have it in a steel drum. Either way....I think the reasons your saw is alive right now has to do with your particular combination of lower compression, a well sealing top end, and you have chosen to run overly rich as your insurance rather than some other options, as many others choose too...but not our OP... Old fuel has to do with how it's stored. It would be less useful if it was kept in an open topped container. You store fuel just like the actual gas station does, then mix when needed. Not everyone does, sadly, not our OP. 



mtngun said:


> I can believe that there was pinging, as evidenced by the broken piston edge, but it's a chicken or egg question. Did pinging lead to overheating, or did overheating lead to pinging ?



I think wear led to overheating. I feel the piston was too worn and leaking, that will help it heat up nice (as evidenced by the blowby). I also agree that burbly rich = cool so he could have still been running this if it was over rich. It would still have been pinging away though until he used other fuel. You cannot get around the clean combustion chamber, pre ign marks on the piston top and head. Would it be rich enough to overcome ping? Maybe but that would have to be pretty fat...there are many options to overcome the shortcomings of poor fuel (for that combination).



mtngun said:


> All theory aside, considering the value of an 880, it's worth buying a vac tester and tach to make sure things are right before putting the saw back to work. Check the fuel lines and fuel filter, too, maybe just replace them to be sure.
> 
> It's a darn shame about the saw.



Good discussion.....it's no fun to have a failure though, and that is a nice saw. 
I might add that the fuel pump diaphram be checked for cracks..which will turn into/are leaks, another source of a vacuum leak though I think I made my failure mode clear.
No one seems to want to follow up on the timing issue. Having a solid state timing box fail offering up too much advance, or physically moving from it's fixed timing location would be a problem...follow right along with what I think happened.


----------



## Andrew96

Kicker_92 said:


> I should probably mention, all my engine experiance is with big V8 4s motors, the 2s repair world is quite new to me.


I started with 2s then moved to 4s, I'm a consultant now for various builders we have around here (cars bikes, sleds, boats...only 1 aviation engine though). I get called in when they are stumped...or cannot get a good tune going. 
The about the only difference is vacuum leaks. On a big V8 a vacuum leak causes some idle games, stumbles..all of which can be dialed out. A 2s...vacuum leaks just cause a meltdown. You cannot have any. You cannot just fire them up and see...you need to check first. If you play with v8s...get out your leak down tester..you'll need 1/2 of it. 



Kicker_92 said:


> As far as acid goes, you'd mentioned a couple differant sources, is there a particular acid to look for on the label?



What you are really after here is muratic acid...but almost any strong acid will work..that's why all the sources. If you are only going to use if for this project...get the smallest container you can. You're after about 50ml at most. I think you'll have to buy 1 liter though. Read the instructions though..it's real acid and will burn your nose eyes and skin..not to mention everything else. 



Kicker_92 said:


> Assuming I can get the cylinder to clean up ok, is there anything else to do while it's apart? On the 4s we'd usually take off any shrap edges or flash that can heat up and cause a preignite, and polish the exaust ports. Does that apply to 2s as well?



No...keep the files away from this one. I think you need to concentrate on how you're going to check everything so this doesn't happen again. Just because I guessed (based on a couple of photos) that you ran poor fuel in a worn top end...I could be wrong. There are tons of things you need to check. 
Did some of your piston end up down near the crank? That needs to get cleaned out? 
You need to check your crank seals don't leak..your case 1/2s (the block)..the whole assembly (the block plus intake manifold which is part of the cylinder) needs to be pressure tested...but I also vacuum test it (too many reasons why to go into here). You'll need to figure out how to do that with fittings and such. Read about it on the chain saw part of the forum. 
How about your ignition timing. What's it's initial..does it curve correct? 
Your fuel pump runs off vacuum...could leak.
Your carb base gasket..carb itself. I know it's just a small looking block..but everything runs off vacuum and needs to be sealed.



Kicker_92 said:


> Our 89 gas is a 5% ethanol mix. I have the option at some stations of a 94 octane, but that has up to 15% ethanol in it. We'll go down to one gas can instead of two, that should keep it down to a week old max. Would you suggest mixing the oil in right away, or only as we need it? I think the Stihl mix has a stabilizer in it.



Warning...issuing free advice here!....I think you need to locate some other fuel source. Try anything that is ethanol free. Another gas station? Mix it on demand. If you can't I'd still go for 94 + ethanol over 89 + little less. Neither are the best choice though IMO.


----------



## huskyhank

And since the OP stated the saw had a new spark plug installed just before it melted down -- when you put it back together be sure to check the plug to see if its the right one for this saw.


----------



## WadePatton

i recalled that someone posted a laundry list of "acids" in this thread. oven cleaner and drain cleaner are not acid. they are base a/k/a lye. don't know if that makes a difference or not. the hardware store sells various acids.

i've used plenty of_ lye _cleaning cast iron, but do not know which is preferred or if both will work on the aluminum here and not the nikasil.


----------



## the westspartan

How old was the gas you were running? 

I teach college sculpture classes and bought an ms180 for the students to rough out shapes with. Ran like a top for the first semester(early spring). Was hardly ever used. Next semester(late fall) a student fueled it up before I had a chance to dump the old fuel from the can he was using. TOAST! in about a tank of gas it was toast. Piston looked just like this one. 

I know these are very different scenarios (light use on homeowner grade saw VS heavy use on a beast of a pro saw) but I imagine bad gas would do the same in either situation.

Good luck.

By the way. I am very strict about freshening my fuel supply now. Lesson learned!


----------



## BobL

A lot of what occasional CS operators think is old mix is just old straight gas. I wouldn't trust any fuel that someone else mixed 6 months ago.


----------



## the westspartan

BobL said:


> A lot of what occasional CS operators think is old mix is just old straight gas. I wouldn't trust any fuel that someone else mixed 6 months ago.



I agree! I don't ever use the school gas in MY saws, just in case. However, it was definately mix he ran through the 180 it was blue. LOL


----------



## BobL

WadePatton said:


> i recalled that someone posted a laundry list of "acids" in this thread. oven cleaner and drain cleaner are not acid. they are base a/k/a lye. don't know if that makes a difference or not. the hardware store sells various acids.
> 
> i've used plenty of_ lye _cleaning cast iron, but do not know which is preferred or if both will work on the aluminum here and not the nikasil.



Both strong acids and strong bases will work on aluminum but Muriatic acid or HCl is the most commonly used for this purpose.


----------



## Kicker_92

Muriatic is common as a pool/spa chemical, is it not? 

I'll give that a shot and see what the cylinder looks like. Learned that the same piston is used for the 880, 088, and 084, so that helps.

While I have this open, any suggestions on improvements for a milling saw? Was thinking of keeping the port timings the same, but widening and smoothing out the ports. 

Any other improments for mid range power? What about thickening the base gasket to lower the compression a bit, reduce the chances of detonation?


----------



## mtngun

Kicker_92 said:


> Any other improments for mid range power? What about thickening the base gasket to lower the compression a bit, reduce the chances of detonation?


I was going to suggest the opposite. More compression is one of the easiest ways to gain power.

But, the logical thing to do is check compression and squish after you bolt the new parts on. I assume you are near sea level, so you should see around 160 psi. If not, I'd be inclined to tweak it in that direction.

I'm not a 2-stroke guru but 4-strokes with aluminum heads can run 9:1 or 9.5:1 compression ratios on cheap gas. OEM Stihls seems to be 8:1 to 9:1, not exactly radical.


----------



## Brmorgan

Kicker, Canadian Tire has Muriatic (Hydrochloric) acid down in the paint/solvent dept (maybe around pool stuff too). It's in a white cylindrical container with blue lettering about 4" round and a foot high or so, and is kept wrapped inside a plastic bag for extra protection. It's not expensive; it's been a while since I bought mine but I think it was 6 or 7 bucks.

As a warning though, this is a STRONG acid. It fumes quite a bit, and if you leave it out in an open container it will very rapidly oxidize and corrode any nearby reactive metals. Be very careful not to sniff the fumes too - they can easily overpower you or burn your lungs; think of swimming pool chlorine but dozens of times stronger. If you get a bit on your skin, don't panic, but do wash it off with lots of water right away. Since water only dilutes acid and can't neutralize it, it can take quite a bit of water to truly wash all the acid away. 

So sad for the 880.  What was it blowing for compression before? I can't imagine a stock 880 having high enough compression to cause detonation / pre-ignition without there being another factor involved. Good ~91 octane should be good to near 200 PSI; I run it in my 180 PSI 181SE without any issues. And I'd be willing to bet there isn't a stock 880 anywhere that is running that high. If it definitely isn't fuel/mix/carburetion/airleak related, and it turns out detonation was the true culprit, I'd also be highly suspicious of the new spark plug being too hot or the ignition being out of time for some freak reason. 

This has been posted many times over in the chainsaw forum, but maybe not here in the milling hangout:
*
READING PISTON DAMAGE EXAMPLES *


----------



## Kicker_92

Got most of the alum off the cylinder, it looks pretty good other than several small grooves through the plating. Even with the plting worn out a bit on that side, I'll put a new piston & rings in and run it for a while. Will clean up the exhaust ports a bit, and knock down any high spots.

I didn't do a compression test on the MS880, I've only measured the 385xp and it was around 140. I'll buy my own comp tester and check it when I get everything back together.

It's a good time to do a BobL style muffler mod too, since this is basically a milling only saw. The parts are all in the dishwasher getting cleaned up (I have a great wife!) so will start working on it this weekend.


----------



## Kicker_92

Here's some pics of the nice clean cylinder. 

The acid took most the aluminum off, but I had to wet sand with some 400 grit to knock down the ridges from the score marks. This wore through the coating below the exhaust port. The area above the port is still good.

I'm thinking it'll be fine to run like this,but would like a second opinion before I spend the time reassembling with a new piston.

Oh, and the squish measured in at approx 0.040", plus another 0.020" for the base gasket. I haven't measured the combustion chamber yet, but there's a lot of space there. Like mtngun pointed out, it seems to be pretty conservative.

The plug:






The clean cylinder:





The exhaust port:


----------



## Coalsmoke

Diesel engines are more my game (worked as a truck and equipment tech for a while), but I rebuild my own snowmobile 2 stroke engines and wouldn't put it back together looking like that (sorry, but it is my honest opinion). There is a place in the valley here that will redo Nikasil. Forget their name but can dig it out if you need it. For what its worth though, I have a saw builder in Abbotsford that gets any serious engine work on my saws. He knows his saws well, and I don't feel like messing up an expensive Husky because I pushed it a bit too far. He has done up a 395XPG for me that screams. If you need his name / number I can get that too. Have it on file here somewhere.

Mr Westspartan, I suspect that the damage done to your 180 was the result of a lean condition and not specifically the age of the gas. With our newer fuels today, you will find that when the gas starts to turn, the engine will lose its top end capacity. Small bore engines can be more susceptible to overly lean or rich conditions.


----------



## mwrunt

the plug looks lean there should be a darker tan atleast on one half of the plug. And in my opinion the cyl is toast. maybe try find a good used one of see if someone makes a cheaper aftermarket. 
I noticed you are in bc it mite be cheaper to get mongoose machine to replate it. They are located in burnaby and do tons of motorcuce jugs. Mite be worth it to look them up and see 


Kicker_92 said:


> Here's some pics of the nice clean cylinder.
> 
> The acid took most the aluminum off, but I had to wet sand with some 400 grit to knock down the ridges from the score marks. This wore through the coating below the exhaust port. The area above the port is still good.
> 
> I'm thinking it'll be fine to run like this,but would like a second opinion before I spend the time reassembling with a new piston.
> 
> Oh, and the squish measured in at approx 0.040", plus another 0.020" for the base gasket. I haven't measured the combustion chamber yet, but there's a lot of space there. Like mtngun pointed out, it seems to be pretty conservative.
> 
> The plug:
> 
> 
> 
> 
> 
> The clean cylinder:
> 
> 
> 
> 
> 
> The exhaust port:


----------



## Coalsmoke

Thanks! Mongoose is the company I was trying to remember. You just saved my brain from at least 3 hours of painful wondering.


----------



## Andrew96

Actually..I don't think that plug looks 1/2 bad for ethanol enriched fuel...at least for mixture...but only because we can only see 1/2 of the plug. The side of the ceramic is pointing the wrong way to really see. The area to look at is down right now. However...it seems all for nothing if the bore won't clean up. Scratch in the chrome = bore is done. 
I did notice one other detail from your latest round of photos. If you choose to have your cylinder replated...and use it again...make sure you confirm the edge I've circled. That's a very important part of the port...a very big port and it's right on the side radius. The picture might not tell the whole story but it looks like the chamfer is not enough in that area. You can see a corresponding mark up the bore from this area but I don't think that has anything to do with the initial failure. However....if you are going to use this bore again after it's rechromed..you should address that. Hmm lets be clear here...address that port BEFORE you get it rechromed. The funny chamfer could cause your right to flutter, not a good place to unload a ring since that is about the hottest area of the whole assembly, and the worst area for the ring. See the missing marks down the bore (for 3/16")?..it's unloaded (bounced off the radius edge) before. 

If you were going to attempt any porting adjustments on this engine..don't just start opening things up, or changing the port timing (raising them). The easy one to see is to adjust your transfer ports instead. With an unbalanced burn pattern like you have..you would keep the longevity of this setup (current issue aside) and still make more power if the intake ports were balanced. Look at that burn pattern on the head...your left transfers cannot keep up with the right (that's why the burn pattern is off centered in that design head). Check your base gasket isn't/wasn't covering some of the port to make your engine lop sided (though it is really quite close...you're not looking for much...a mismatched base gasket to port could cause that).


----------



## losttheplot

This may have been said already.

Whatever killed your saw must be fixed before you run it again !

If there is any condition, such as an air leak or fuel starvation that caused the saw to break it will do the same to the new piston/cylinder. 

Examine everything VERY carefully.
There is nothing worse than rebuilding a motor twice.


----------



## mtngun

Kicker, thanks for the excellent pictures. This is a painful experience but at least we are all learning something from it.

I'm of the school of thought that spark plug readings can't be relied on, but for what it is worth, your spark plug is consistent with a lean condition.

Here is the plug from my milling saw. I just took this picture a few minutes ago. Last time it ran the weather was near zero (F) and I didn't bother to retune so the saw was running leaner than normal.





Now compare that to your squeeky clean plug.


----------



## huskyhank

mtngun said:


> Kicker, thanks for the excellent pictures. This is a painful experience but at least we are all learning something from it.
> 
> I'm of the school of thought that spark plug readings can't be relied on, but for what it is worth, your spark plug is consistent with a lean condition.
> 
> Here is the plug from my milling saw. I just took this picture a few minutes ago. Last time it ran the weather was near zero (F) and I didn't bother to retune so the saw was running leaner than normal.
> 
> 
> 
> 
> 
> Now compare that to your squeeky clean plug.



*I second the above.*

and...

What plug does Stihl tell you to use?
What plug was in the saw when it died?


----------



## Coalsmoke

Plug looks like the right one, but I agree, definitely been running hot.


----------



## excess650

.040" squish without a base gasket seems pretty wide, and another .020" makes it really wide, IMO. You really should check with the guys on the chainsaw board to see what they recommend for an 088/880, but I set my 660 up at .025" with base gasket. There are other guys who will set them up at .020" and mod the ports as well, but they're looking to increase RPMs. I'm a bit more conservative in that regard, and would rather have my milling saw run a little slower and cooler so as to live considerably longer.

I run 91-93 octane pump premium that I'm sure is laced with 10% ethanol, but that is what is available locally. My usual mix oil is a synthetic blend (Echo Powerblend) mixed 40-1, doesn't make excessive carbon or smoke, and leaves an oily coating on the piston. Being on the paranoid side about the fuel, I generally don't keep it around more than a month, and if in doubt, dump it out.

My milling saw is also tuned rich so as to limit RPM and increase cooling during longer cuts. If you're running stock spec RPM while milling, you're asking for trouble.

Your cleaned cylinder looks pretty bad to me. Those that I've cleaned and re-used have looked almost new. With the price of 880s, I would choose to err on the side of caution and get a new P&C.


----------



## Andrew96

mtngun said:


> Kicker, thanks for the excellent pictures. This is a painful experience but at least we are all learning something from it.
> 
> I'm of the school of thought that spark plug readings can't be relied on, but for what it is worth, your spark plug is consistent with a lean condition.
> 
> Here is the plug from my milling saw. I just took this picture a few minutes ago. Last time it ran the weather was near zero (F) and I didn't bother to retune so the saw was running leaner than normal.
> 
> 
> 
> 
> 
> Now compare that to your squeeky clean plug.



OK, I better stand as corrected ...all I can do is blame it all on the colour rendition of my monitor..and the photos. We know Mtnguns saw runs very nice...and he stated it was a little on the lean side prior to pulling the plug (the photos I see look very dark...but hey...must be my monitor!). When seeing a comparison, on the same monitor...I can see the pretty lean plug. However, you can also see mtnguns doesn't have any deposits from preignition either on the ceramic..or the electrode. So...though it's pretty lean..the preignition signs are still there (on the plug, on the piston, and in the head). Did your fixed timing move? Did the box fail so it was too advanced? If you are confident that the fuel was good...something else caused the preignition...I don't feel it was just lean temps. There is still something missing to the story. Lean yes...and?


----------



## mtngun

Andrew96 said:


> We know Mtnguns saw runs very nice...and he stated it was a little on the lean side prior to pulling the plug (the photos I see look very dark...but hey...must be my monitor!).


I meant lean compared to how it is normally tuned. Normally tuned to 12,000 WOT, on that cold day it was pulling 12,500 WOT. 

I feel Kicker's pain.


----------



## isaaccarlson

*Just where do you dump it?*



excess650 said:


> Being on the paranoid side about the fuel, I generally don't keep it around more than a month, and if in doubt, dump it out.



I hope you don't dump it on the ground.


----------



## Kicker_92

Andrew96 said:


> Did your fixed timing move? Did the box fail so it was too advanced?



How do you change the ignition timing on these? The module is mounted with two screws, I dont see how you could adjust it?


----------



## Brmorgan

isaaccarlson said:


> I hope you don't dump it on the ground.



I dump my old gas in the car or quad. They don't seem to mind at all, and if I do suspect some water I'll throw a bit of methyl hydrate in with it to help burn it off.



Kicker_92 said:


> How do you change the ignition timing on these? The module is mounted with two screws, I dont see how you could adjust it?



I can't speak for an 880 per se, but a lot of ignition sets have elongated mounting holes, so you can loosen the screws and rotate it a couple degrees one way or the other. This was the case on the 041s I've been working on.


----------



## Andrew96

Kicker_92 said:


> How do you change the ignition timing on these? The module is mounted with two screws, I dont see how you could adjust it?



Well it might be a fixed position (non adjustable) pickup (I don't have an 880). Are the screws tight? Did the box fail and it's advanced? Something changed...providing the fuel was good.
You'll have to put the ignition question on hold until it's all back together, you complete all the pressure tests, and get to fire it off. You might choose to check the timing but usually when the solid state ignitions fail..the timing is stuck, or non existant. It will make it interesting to start if it's stuck. Testing your timing is just one detail on your list of checks.


----------



## timberwolf

Looks like the pistong just got too hot over the exhaust side. Lots of things can tip the balance, plugged up cooling fins or fan cover, running lean on fuel.

To make the 880 into a milling machiene I would be inclined to get the squish down too about .030, this will help prevent preignition and heating of the exhaust side of the piston crown. Get an older 088 non rev limited coil so the saw AF mixture can be set with less guessing, open the muffler up and richen the jets. The extra HP gained by the saw not fighting the muffler restriction will allow it to work a little less to get the same work done. Same goes for some basic port clean up work. Keeping the RPM up with a little extra HP lets the fan do more cooling. Bogging the saw on a mill is real tough on it, produces a lot of heat but it slows the fan reducing cooling and then with the saw falling out of the powerband the cut takes longer (tripple whammy).

Good fuel and oil always, don't let the saw run dry in the cut. Keep the fan and cooling fins clear, let the saw warm up and cool down a little before and after big cuts and chain sharp.

The vast majority of saw ignitions are dead simple and don't have any advance curves. They may retard a bit at very low RPM for starting, but I have seen no significant timing shifts from idle upto WOT no load.


----------



## Kicker_92

timberwolf said:


> To make the 880 into a milling machiene I would be inclined to get the squish down too about .030, this will help prevent preignition and heating of the exhaust side of the piston crown.



Thanks Timberwolf, I've been reading through some of your posts on your 880 buildup, thats an impressive machine!

I've decided to do a bit of work on the cylinder before I reuse it, have decked about 0.035" off to give me around 0.025" squish. It slipped when I was milling (no lathe), so I might have taken a bit too much off. I'll increase the base gasket or dome the piston a bit if it went too far.

I've already widened the exhaust and intake ports to about 2mm from the edge of the piston skirt, and and now working on smoothing up the exhuast passage. I'll clean up the flash off the piston tomorrow.


----------



## Kicker_92

BobL or Timberwolf:

Do you guys have a stock compression reading from your MS880?


----------



## BobL

timberwolf said:


> To make the 880 into a milling machiene I would be inclined to get the squish down too about .030, this will help prevent preignition and heating of the exhaust side of the piston crown. Get an older 088 non rev limited coil so the saw AF mixture can be set with less guessing, open the muffler up and richen the jets. The extra HP gained by the saw not fighting the muffler restriction will allow it to work a little less to get the same work done. Same goes for some basic port clean up work. Keeping the RPM up with a little extra HP lets the fan do more cooling. Bogging the saw on a mill is real tough on it, produces a lot of heat but it slows the fan reducing cooling and then with the saw falling out of the powerband the cut takes longer (tripple whammy).
> 
> Good fuel and oil always, don't let the saw run dry in the cut. Keep the fan and cooling fins clear, let the saw warm up and cool down a little before and after big cuts and chain sharp.



All this is one reason why I installed a temp gauge. As you say, pushing the saw hard so it drops of the power curve and sits at say 6500 - 7000 rpm sees the temp rise noticeably. This is why I was slightly concerned with using an 8 pin with mildly aggressive rakers but it only dropped the operating RPM in hardwood by a couple of hundred rpm

My sensor is not ideally located (it's in a small gap above the exhaust manifold) so what the sensor measures is the temperature of the cooling air after it has passed over part of the cylinder. But it is still better than nothing. 

As reported by the sensor, if the ambient air temp is 70F the saw at idle eventually reaches about 140F.

Milling sees it increase quickly but only by about 20F, then the temp rise slows down and the final operating temp depends on 101 variables. eg
How hard the saw is being pushed
Wood hardness
Amount of contact between wood and saw or width of cut
Sprocket size
Size of chain
Sharpness of chain
Depth of rakers

It's easy to see the effect or some of these factors eg the temp increases quicker if the saw is pushed hard and dropping the RPM, but I can't really see any temp difference between using 7 or 8 pin sprockets.

As I said, once the saw has reached a nominal operating temp ~160F, the temp continues to increase. All being well, the final temp at the end of the slab (~170F) is a useful indicator of how things are going. If I don't touch up the chain and cut another slab the temperature at the end of that slab can be 190F. 

When ever the saw has been working (eg sensor measuring ~170F, ) and then left to idle (or stopped) the temp at the sensor rises immediately by about 30F at idle (and over 50F if stopped) because the amount of cooling has dropped off or ceased. 

I then leave the saw to idle until it reaches <150F - this can take as much as 2 minutes.


----------



## billstuewe

BobL, Where did you get your temp guage? What kind? and How much$?

Thanks,
Bill


----------



## BobL

billstuewe said:


> BobL, Where did you get your temp guage? What kind? and How much$?
> 
> Thanks,
> Bill



It's from a company that supplies parts for RC vehicles.
www.traxxas.com/products/nitro/jato/trx_jato_accessories.htm


----------



## Kicker_92

I've got the new piston now, and have a tach borrowed to help tune with.

So on a coil limited saw, how do you tune the fuel mixture? I've tried searching but haven't found much. The 880 I believe it limited around 11,000 rpm?


----------



## mtngun

Kicker_92 said:


> I've got the new piston now, and have a tach borrowed to help tune with.
> 
> So on a coil limited saw, how do you tune the fuel mixture? I've tried searching but haven't found much. The 880 I believe it limited around 11,000 rpm?


Good on you for scrounging a tach. 

You'll have to verify the factory spec for WOT. Lean the H until it hits the limiter. When it hits the limiter, your tach will go crazy and give erratic readings. Then richen the H until the tach starts behaving again, and the revs are at least 500 rpm below the limit. 

Traditionalists will insist that you get an unlimited coil and tune by ear, but Lakeside was comfortable tuning a limited saw with a tach. Lakeside also recommended tuning a miling saw to less than the factory rpm spec. 

You are going to have the cylinder replated, right ? Let us know how that works out.


----------



## BobL

mtngun said:


> Good on you for scrounging a tach.
> 
> You'll have to verify the factory spec for WOT. Lean the H until it hits the limiter. When it hits the limiter, your tach will go crazy and give erratic readings. Then richen the H until the tach starts behaving again, and the revs are at least 500 rpm below the limit.



That's basically what I do.

The coil is limited to 12,000 rpm so you are safe on 11,500.

I have a muffler mod on mine so it really wants to run above that but I set it on 11750 which is a couple of hundred revs above the 4 stroke burble. 

I find sitting on around 9500 in the cut gives me a good compromise between cutting speed, raker depth and temperature.


----------



## Kicker_92

*It's Alive!*

Fired up the saw this evening. Had a bit of trouble as I decked a bit too much off the cylinder (it slipped in the clamp while milling). Ended up at 0.013" squish. 

Not a big deal, cut a new base gasket to bump that back up to 0.025". Pulled easy for the first couple pulls, then burped. Next pull with choke off fired right up. Don't have a gauge to check compression with, but it'll take a strong shoulder even with the de-comp!

Didn't have a bar & chain on it at home, so will have to hold off on tuning until Sunday. Definately sounds a lot more mean than it used to, a lot more 'pop' in the exhaust note.

I'll set the mixture to 11,500 the see how it does in the cut. Still have to make a new plate and pipe for the exhuast too.


JUst want to thank everyone for the tips and help. Looking forward to getting it back on the mill next week and making some sawdust!


----------



## mtngun

Glad it is running again. I hope you tested it for leaks ?


----------



## robertjinnes

*Not acid---lye*

Acid will eat most metals. Lye (DRANO) will eat aluminum faster than anything else --Look at the crystals, there are chunks of aluminum mixed in. Lye eats aluminum and creates heat---TADA unplugged drain. When using LYE or acid, use caution both for you and for the cylinder. Don't dump lye in a bucket and submerge the jug. You'll actually eat the threads out everything, including the spark plug hole. Place a couple dozen granules into the cylinder near the worst aluminum build up, dribble water on them and mush the mix around on the aluminum. Dump and rinse after 30 seconds to a minute. Repeat as and where needed. Just cleaned up a Huski 3120 jug that had burned a large portion of upper ring land and then chewed up 1/3 of the top piston ring. Thanks to Nikasil, After lye and about 2 minutes with a fine long stone cylinder hone, I was left with one scratch where a piece of ring had left a minor scratch from the top of the cylinder and down the cylinder wall approx 3/8 inch with the worst above where the ring will ever hit--- $40 plus shipping for a new piston, $13 for bearings and $19 plus shipping for a complete gasket set including crank seals. That $72 changed a $200 parts saw back into a $1000 monster for my Alaskan Mill. 
Good Luck
Bob the Treeman


----------



## Oden

*Cylinder?*

Kicker
What did you end up doing with your cylinder? if replated how much did that cost?

thanks
Oden


----------



## Kicker_92

Oden said:


> What did you end up doing with your cylinder? if replated how much did that cost?



We descided to re-use the cylinder. With the age of the saw, and the high cost of a replacement cylinder, it just wasn't worth putting more money into.

And I really couldn't do some major port work on a new or re-plated cylinder.  Got the muffler opened up to around 3/4" (19mm), should hopfully get a chance tomorrow night to test and tune it. It sounds downright angry now, looking forward to throwing some chips. 

Maybe a 9-pin will be an option now?


----------



## Kicker_92

BobL said:


> The coil is limited to 12,000 rpm so you are safe on 11,500.



Bob, 

How old is your 880? I put the tach on mine tonight, and the coil seems to cut out exactly at 10,500 rpm.

It four strokes right up to that point, so I tuned it in the cut to run about 9,000 rpm. Burbles as soon as you let the pressure off the mill, but runs nice in the cut. Only had a 20" wide cut setup to work with so not a great test, but very happy with the extra grunt it's picked up!

I'll have to get it into some 40" wood and see how she does.


----------



## BobL

Kicker_92 said:


> Bob,
> 
> How old is your 880? I put the tach on mine tonight, and the coil seems to cut out exactly at 10,500 rpm.


Mine is a 2008 model.



> It four strokes right up to that point


That sounds like your H screw is set too rich, have you leaned it out as per manual?


----------



## huskyhank

Kicker_92 said:


> snipped.....
> 
> Burbles as soon as you let the pressure off the mill, but runs nice in the cut.



What BobL wrote and--

Run it like this for a cut, shut it off, pull the plug and look at it. If the plug is black and oily you might lean it out and re-check. If its just real dark brown I'd leave it alone. But you're not far off - if its running good in the cut it may be just fine as is, especially while you're breaking in the new parts. Don't go too far lean or you'll be re-building it again.


----------



## Kicker_92

BobL said:


> That sounds like your H screw is set too rich, have you leaned it out as per manual?



I'm thinking they might have slightly differant limiters since mine would be a bit older than that. (2006?) 10,500 is fine, it won't hit that in the cut, but might keep an eye out for an unlimited coil for easier tuning.

I'm sure it's set too rich, but it does smooth out once theres some extra resistance. Chain is sharp and rakers are set at 8°, and it's still asking for more in a 20" wide cut.

We'll be keeping it on the rich side for milling, can't afford to melt any more parts. It's definatly running a *lot* cooler with the exhaust mods.


----------



## mtngun

Kicker_92 said:


> I'm sure it's set too rich, but it does smooth out once theres some extra resistance. Chain is sharp and rakers are set at 8°, and it's still asking for more in a 20" wide cut.


That's the nice thing about using an 880 -- it's just loafing along instead of straining like a 90cc saw.


----------



## Haywire Haywood

Kicker_92 said:


> rakers are set at 8°.



I don't quite understand what you mean here.. Rakers are usually set in thousandths (below tooth level). I usually use a .030 guide on my firewood chain.

Ian


----------



## mtngun

Haywire Haywood said:


> I don't quite understand what you mean here.. Rakers are usually set in thousandths (below tooth level). I usually use a .030 guide on my firewood chain.


Ian, members of the elite AS milling forum take chain sharpening to a whole new level, using a digital protractor to set rakers. This is a spin-off of the File-o-plate method which attempts to maintain rakers at a more-or-less constant angle relative to the cutter.


----------



## MR4WD

Kicker_92 said:


> I'm thinking they might have slightly differant limiters since mine would be a bit older than that. (2006?) 10,500 is fine, it won't hit that in the cut, but might keep an eye out for an unlimited coil for easier tuning.
> 
> I'm sure it's set too rich, but it does smooth out once theres some extra resistance. Chain is sharp and rakers are set at 8°, and it's still asking for more in a 20" wide cut.
> 
> We'll be keeping it on the rich side for milling, can't afford to melt any more parts. It's definatly running a *lot* cooler with the exhaust mods.



Talk to tree sling'r, he'll set you up with an unlimited coil. What are you using to set your rakers? Best I could come up with was your typical analog angle finder. It's pretty big and cumbersome. I should get BobL to send me one like his! Do you have any pics of your muffler mod?


----------



## BobL

MR4WD said:


> Talk to tree sling'r, he'll set you up with an unlimited coil. What are you using to set your rakers? Best I could come up with was your typical analog angle finder. It's pretty big and cumbersome. I should get BobL to send me one like his! Do you have any pics of your muffler mod?



Digital Angle Finders (DAF) are much cheaper in the US than I can get them for here. see http://www.wixey.com/anglegauge/index.html

I also have one of the cheaper ($19.95) ones, but it chews thru batteries much faster than the more expensive ones, they also have problematic zero switches.

If you don't want to go to the bother of using a DAF then an FOP type gauge is superior to a fixed depth gauge especially as a cutter wears.


----------



## Kicker_92

I use the same Wixey gauge as Bob, we actually have them here at work for measuring angles on parts.

I think it'd be around equivalent to 0.040" raker depth on a new chain at 8°.


----------



## Kicker_92

Was going good last night, then started surging while in the cut after it had warmed up. Woudl go from screaming then bog to the point of stalling.

Seems like an air leak. I' forgotted to tighten up the rubber boot fromt eh carb to cylinder, so will try that and see how it tests.


----------



## BobL

Kicker_92 said:


> I use the same Wixey gauge as Bob, we actually have them here at work for measuring angles on parts.
> 
> I think it'd be around equivalent to 0.040" raker depth on a new chain at 8°.



8• is equivalent to 0.035 on a new 3/8 chain




Kicker_92 said:


> Was going good last night, then started surging while in the cut after it had warmed up. Woudl go from screaming then bog to the point of stalling.


Is that while milling or just by itself?




> Seems like an air leak. I' forgotted to tighten up the rubber boot fromt eh carb to cylinder, so will try that and see how it tests.



If is is an air leak you need to vac&press test the whole thing.

One more thing, when using the WIXEY DAF the rounded corners and inset magnets limit the contact area over which the angle measurements can be made.






This diagram shows on the left a side cross section of the DAF, The two arrows show the contact area that should be used. If a cutter or raker encroached into the inset magnet spots or rounded corner areas an incorrect angle reading will be made.

To facilitate this the right hand side diagram shows how I clamp a rebated wood block to the blade to ensure only the small contact area is used.


----------



## Kicker_92

BobL said:


> Is that while milling or just by itself?
> 
> If is is an air leak you need to vac&press test the whole thing.




It was doing it when in the cut, which would make sense since it's developing vacuum. There's a good chance it was just from missing the hose clamp on the carb to cylinder connection. The only other item would be a leak at the base gasket. Will check that after if it still has the issue.

Searching through the archives, you had something similar on you 076?


----------



## Brmorgan

BobL said:


> 8• is equivalent to 0.035 on a new 3/8 chain
> 
> 
> 
> Is that while milling or just by itself?
> 
> 
> 
> 
> If is is an air leak you need to vac&press test the whole thing.
> 
> One more thing, when using the WIXEY DAF the rounded corners and inset magnets limit the contact area over which the angle measurements can be made.
> 
> 
> 
> 
> 
> This diagram shows on the left a side cross section of the DAF, The two arrows show the contact area that should be used. If a cutter or raker encroached into the inset magnet spots or rounded corner areas an incorrect angle reading will be made.
> 
> *To facilitate this the right hand side diagram shows how I clamp a rebated wood block to the blade to ensure only the small contact area is used.*



Translation for North Americans: Rebated = Rabetted over here. In North America, "Rebate" is a term used to describe a legal way for companies to rip people off via the postal service. 


I guess maybe I _should_ take the time to get my milling chains dialed in once in a while like you do, but for the amount (and relative softness) of wood I mill, I'm just not sure the cut time I might save would offset the extra time spent. And as far as firewood chains go, I don't use a gauge of any sort. Just use a flat guide for the round file, and eyeball pretty much everything incl. cutter length, angle, and raker depth. If I really rock a chain or need to even everything up for some reason, I use the clamp-on Oregon file guide which works well enough for what I need. I could probably do a bit better but my firewood chains still seem to cut like a raped ape; I can't say I ever notice much performance falloff between brand-new and after being filed half a dozen times. And my milling times and speeds seem to be comparable to others' experiences here who have similar setups and encounter similar woods, such as Mtngun.

Kicker, I hope you get that suspected air leak sorted out pretty quickly, or you'll be right back to square one in short order.


----------



## BobL

Brmorgan said:


> Translation for North Americans: Rebated = Rabetted over here. In North America, "Rebate" is a term used to describe a legal way for companies to rip people off via the postal service.


Thanks for the clarification.



> I guess maybe I _should_ take the time to get my milling chains dialed in once in a while like you do, but for the amount (and relative softness) of wood I mill, I'm just not sure the cut time I might save would offset the extra time spent.


I agree.



> And as far as firewood chains go, I don't use a gauge of any sort. Just use a flat guide for the round file, and eyeball pretty much everything incl. cutter length, angle, and raker depth. If I really rock a chain or need to even everything up for some reason, I use the clamp-on Oregon file guide which works well enough for what I need. I could probably do a bit better but my firewood chains still seem to cut like a raped ape; I can't say I ever notice much performance falloff between brand-new and after being filed half a dozen times. And my milling times and speeds seem to be comparable to others' experiences here who have similar setups and encounter similar woods, such as Mtngun.


I'm the same for firewood and bucking - especially if I'm cutting in dirty conditions.

The cutting angle approach to setting rakers is about understanding what is going on and comes into its own on big hardwood slabs and short cutters when I clearly see the difference between dust and chip generation. Old timers never worried about specific raker depths/angles, they just kept on filing rakers until they started making chips again.


----------



## rxe

I like the temperature measurements upthread. Anything to stop the paranoia about whether I've got the mixture rich enough or whether the saw is acting "funny"...

I'm going to get a couple of these:

http://www.omega.co.uk/ppt/pptsc.asp?ref=WT&Nav=tema03

...and bolt them to the exhaust stud of my 070 and 090 milling saws. They're just Type K thermocouples, and I happen to have a meter to read them. The meter can read two at a time, so out of interest I might bolt another to the base of the cylinder head as well.


----------



## Kicker_92

*Update:*

Well, the vacuum / pressure test didn't reveal anything useful. I managed to get the cylinder bolts cranked another 1/8th turn though. There's no way of pressure testing when it's hot, so we'll have to see if that does it.

Our excavator blew a head gasket, so the sawing will be on hold a couple week while we try to fix that. Will update if I figure out the problem.


----------



## mtngun

Kicker_92 said:


> Well, the vacuum / pressure test didn't reveal anything useful. I managed to get the cylinder bolts cranked another 1/8th turn though.


At least you ruled that out. 

Surging sounds like a fuel problem, as you suggested earlier. Keep us posted.


----------



## Kicker_92

mtngun said:


> At least you ruled that out.
> 
> Surging sounds like a fuel problem, as you suggested earlier. Keep us posted.



Haven't rules an air leak out entirely, but it tests well when cold. I would assume any leak major enough to cause a drastic surging like this would be significant enough to not only occur when hot.

Waiting for the headgasket to come in for our machine, so we cut up another 13"x16"x14ft post tonight. Put in a new plug just to rule that out. It went well until about halfway through, when it started surging again.

The interesting part is that is I kep the throttle at about half, the rpms stayed a little bit lower but it continued to cut normally, just with less power. As soon as I opened the throttle too much, it would start surging. 

This really leads me to believe that something is going on with the carb. I tried to cover the "dirty air filter" port, but the tape would't stick and stay in place. Will bring something along next time to block it off and see what happens.

I love the way this saw pulls though the wood now. Top end hasn't changed much, but it's got a lot more grunt down low. Ripping through a 16" wide cut was like butter, at least until it started surging.


----------



## Andrew96

Is you fuel tank vent clean? You could be pulling a vacuum on your tank. Next test..when it starts surging...reach over a pop the fuel cap open.


----------



## BobL

Kicker_92 said:


> Haven't rules an air leak out entirely, but it tests well when cold. I would assume any leak major enough to cause a drastic surging like this would be significant enough to not only occur when hot.
> 
> Waiting for the headgasket to come in for our machine, so we cut up another 13"x16"x14ft post tonight. Put in a new plug just to rule that out. It went well until about halfway through, when it started surging again.
> 
> The interesting part is that is I kep the throttle at about half, the rpms stayed a little bit lower but it continued to cut normally, just with less power. As soon as I opened the throttle too much, it would start surging.
> 
> This really leads me to believe that something is going on with the carb. I tried to cover the "dirty air filter" port, but the tape would't stick and stay in place. Will bring something along next time to block it off and see what happens.



It does sound like the carby, Have you pressure tested the carby? 

BTW it is possible do a hot or at least a warm pressure tests. Set up the pressure testing gear and then use a hot air gun to heat the cylinder on the head and the exhaust side. Then do the pressure and vacuum tests. I presume you did both? To get the cylinder hot enough you need a way to blank off the exhaust port other than rubber, telflon sheet is one possibility.


----------



## mtngun

Carbs can be a pain to troubleshoot. In the ideal world, you'd swap carbs with your buddy's 880 and see if that fixes the problem. Then you would know for sure that you need to dig into the carb.

I don't remember if you did a carb kit and welch plug job during this rebuild ? Ditto fuel lines and fuel filter ?

Sounds like its going to be an awesome milling saw once the demons are exorcised.


----------



## Kicker_92

Andrew96 said:


> You could be pulling a vacuum on your tank.



That was actually one of the first things I tried, unfortunatly no change with the tank open or closed.




BobL said:


> It does sound like the carby, Have you pressure tested the carby?



How do you pressure test the carb? Do you have a link or a manual for this?





mtngun said:


> I don't remember if you did a carb kit and welch plug job during this rebuild ? Ditto fuel lines and fuel filter ?



Didn't touch any of them, only pulled the piston / cylinder. Thats why I'm leaning toward it being a problem with the increased airflow.


----------



## mtngun

Kicker_92 said:


> Didn't touch any of them, only pulled the piston / cylinder. Thats why I'm leaning toward it being a problem with the increased airflow.


Sounds like you are figuring things out.

Sometimes an internal passageway in the carb gets obstructed, or a check valve gets gummy, and it can drive you crazy trying to figure it out. The carb kit/welch plug route may make a noticeable improvement. I did one on my 066 and it fixed a mysterious idle problem, even though I didn't find anything out of the ordinary inside the carb. 

I was thinking to order one of those ultrasonic cleaners that they are talking about on the chainsaw forum because I've had my share of stubborn carb troubles over the years.

I had a saw that liked to stumble and die in mid cut. I'd wait a few minutes and restart it, and it would run for a few seconds or a few minutes until the process repeated itself. Turned out to be a dirty fuel filter. I just blew the filter out with compressed air and that fixed the problem.


----------



## Andrew96

mtngun said:


> I was thinking to order one of those ultrasonic cleaners that they are talking about on the chainsaw forum because I've had my share of stubborn carb troubles over the years.



Mtngun.....go for it. Once you get one...you'll wonder how you ever fixed anything before. I've had one for years. Just don't tell anyone you have one...soon you'll be doing all kinds of old carbs and anything else that has any sort of crazy shape to clean up. Get the biggest one you think you'll ever need. Big enough to put a monster 4bbl in..or some giant throttle body. Does wonders cleaning aluminum prior to welding, etc. Yamaha makes a carb cleaner that is magic with an ultrasonic cleaner...best stuff I've ever found. All kinds of dirt shows up after a good cleaning even on things that were working seemingly fine.


----------



## BobL

Kicker_92 said:


> How do you pressure test the carb? Do you have a link or a manual for this?



I find it hard to imagine trying to sort out this kind of problem without a manual.

I'd start by giving the carby a thorough clean. 

Then I'd go the carby kit.


----------



## jaycky

Fuel is the life of the saw.
My buddy has a stash of gas on property and it's been awhile in the jerry cans I will not use it due to cold hot causing condensation aka water build up. He has mentioned he killed a saw in the blink of an eye last time getting wood for town and he thinks it's from screw turning on him I think it's poor fuel. But we could argue about this for ever or I could try his fuel on my saw and see what happens! Not...
Anyways I'm not screwing around with my 880 and when I start milling it gets a simple cheap and easy fix a temp gauge. I don't know why others don't just get one they under 50 bucks and it's like a triple life line...


----------



## jaycky

Oh while running shop in alberta do you have any idea how many issues we had with the dumb asses parking diesel trucks inside for the night after a -40 day it's not a great idea unless you were to top up all tanks which they never did. Within days failures on pumps engines and on and on. Not to say how much diesel fuel anti gel they added? One night equipment developed mega water condensation In fuel tanks after a week things weren't running . People just don't think . But point is fuel left out all day in sun expansion cold contraction it kills fuel so just mix what's needed and keep the main batch in a cool area store it proper and should be golden. I have read big saws over certain cc's should be mixed at 33.1 so if you did 35.1 or even 40.1 saw should be great and back to setting saw up every-time before getting milling! But cheapest insurance is a temp gauge IMO


----------



## BobL

jaycky said:


> . . . . . when I start milling it gets a simple cheap and easy fix a temp gauge. I don't know why others don't just get one they under 50 bucks and it's like a triple life line...



I wouldn't rely on an external contact temperature gauge to prevent overheating. By the time these gauges register the temp that will overcook a saw the saw will be toast. A better gauge would be an EGT but finding one that will run on a small battery and that is physically robust enough to survive on a powerhead could be tricky. Most EGTs are 12V for motor vehicles and not suitable to locate on a powerhead. I would look into the RC accessory market and if you find a good one let us know.


----------



## jaycky

http://www.trailtech.net/722-et3

What you think if this?


I was more a less thinking tune saw before work and keeping eye on it in mill cut to keep it in the range basically if something starts to move up then double check? Just a cheap insurance on an expensive saw


----------



## BobL

jaycky said:


> http://www.trailtech.net/722-et3
> What you think if this?



That's more or less what I have and being a contact thermometer and will lag too far behind the real temp inside the saw. 
An EGT gauge will be a lot quicker


----------



## jaycky

Hmmm


----------



## Rx7man

Just speaking from my experience with my old husky saws, I noticed a slight power improvement running a bit richer than 40:1 when I had to make extended heavy cuts, and once they were ported, they really appreciated the extra oil of 32:1. If I do mostly limbing, and cutting small stuff, the leaner mix is fine. I had the compression on mine bumped up to 185PSI @ 1200ft elevation.

On a saw that cuts for a long time without being let up, like on a mill, I think I'd run a little more oil on it.


----------



## BobL

Rx7man said:


> Just speaking from my experience with my old husky saws, I noticed a slight power improvement running a bit richer than 40:1 when I had to make extended heavy cuts, and once they were ported, they really appreciated the extra oil of 32:1. If I do mostly limbing, and cutting small stuff, the leaner mix is fine.



There's no such thing as a "lean mix".
Leaness and richness refer to the "air to gas" ratio.
"Gas to lube" ratios are just "gas to lube" ratios, and should not be confused with the previous.

Running lower "oil to gas" ratios without retuning the saw will reduce the amount of gas relative to the amount of air taken up through the carby, which actually ends up "leaning the saw" and that's why it may seem like there's more power. It might seem like it's taking more care of a the saw but it's actually pushing things the wrong way so it is really important to retune the saw and make it rich using the H screw.

The extra lube actually does little to nothing towards cooling the internals of the saw, that is done by the unburnt gas. Modern saws will in fact run happily with very little lube in the mix (even a 100:1) but you'd have to be careful about getting the ratio, and tuning the saw , right because a slight mistake the wrong way will be a problem. 50:1 is recommended by manufacturers because that is about the practical limit that operators (especially in the field) can make up without getting into trouble. 

The majority of saws that get cooked, especially when milling, are a result of running too lean i.e. high "air to gas ratios" , irrespective of the lube to gas ratio used. Extra lube in the mix won't save the saw from frying and in fact may be counterproductive.

My experience is that using extra lube just generates an increase in the invisible fog of unburnt oil and smoke suppressant gunk around the operator and ratios of 25:1 give me a headache., and my clothes hair and chaps are greasier than usual after a full days milling.


----------



## SDB777

Someone must have been reallllly bored to go back into a topic that is 4-1/2 years old




Scott (whew, shoveling is hard) B


----------



## Rx7man

I got my information from http://forum.dirtrider.com/discussion/7169620/spooge-101-/p1

I agree that too much isn't good, but too little is more costly more quickly. a little more oil supposedly helps seal the rings better and leads to more power, I have distinctly noticed the difference between a 40:1 mix and a 32:1 mix... would be interesting for chadih to run a dyno test.
Yes, more oil in the fuel can be counterproductive if the air fuel mix isn't adjusted.

But I'm going to continue using the term "lean mix", because if you really get down to it, "Lean" means Not fat, and that refers to oil!.. There is a difference between not enough fuel in the air, and not enough oil in the fuel


----------



## Haywire Haywood

Rx7man said:


> But I'm going to continue using the term "lean mix", because if you really get down to it, "Lean" means Not fat, and that refers to oil!.. There is a difference between not enough fuel in the air, and not enough oil in the fuel



Bob's right, but since using the correct terminology isn't a requirement, carry on.


----------



## BobL

The reason I keep responding to this incorrect terminology every time it comes up in this forum is to protect newbs who might otherwise think that protecting the saw while milling just requires using more lube in the mix and they don't understand that retuning is needed. If their saw is already borderline "lean" then the extra oil can push it further into "leanness".


----------



## Kicker_92

SDB777 said:


> Someone must have been reallllly bored to go back into a topic that is 4-1/2 years old
> 
> Scott (whew, shoveling is hard) B



Wow, didn't realize it's been that long! That same MS880 is still up and running now. High compression, lots of port work, and running 3/8" 0.050" chain, it chews wood pretty well.
I have a Woodland bandmill now, so only use the alaskan to get logs into quarters now.

Even at only 9hp, the bandmill is just much more efficient.

Thanks for bringing back this old thread! Next will be the old "CSM like a swing mill" one... 

Ryan


----------



## mdavlee

The more oil you use the better the ring seal for more power. 16:1 will make more power but will choke you out. You have to tune the carb to compensate for the oil displacing the gas and richer the H screw


----------



## jaycky

I've been reading these threads scouring actually debating on leaving my 880 stock with limited carb now does this mean I'm in the already lean department? Jesus I got to say the fear factor has made me wonder or re think about getting this saws carb reworked or should I just leave it alone?


----------



## betterbuilt

jaycky said:


> I've been reading these threads scouring actually debating on leaving my 880 stock with limited carb now does this mean I'm in the already lean department? Jesus I got to say the fear factor has made me wonder or re think about getting this saws carb reworked or should I just leave it alone?


I thought the 880 had a limited coil, not a limited carb.


----------



## jaycky

Yea what he said the adjustment on this ms 880 is very little caps limiting further carb adjusting I meant. Is it fine cutting caps and leaving coil as it is ? All these threads have made me paranoid as $&)@

The last thing I want is to pooch this thing milling.. I am actually doubting myself with this saw now. Last thing I want is to burn it up so I've been scouring threads reading as much info as possible every time I read something good I find 4 things bad said... Set my mind at ease please...


----------



## betterbuilt

jaycky said:


> Yea what he said the adjustment on this ms 880 is very little caps I meant. Is it fine cutting caps and leaving coil as it is ? All these threads have made me paranoid as $&)@
> 
> The last thing I want is to pooch this thing milling.. I am actually doubting myself with this saw now. Last thing I want is to burn it up so I've been scouring threads reading as much info as possible every time I read something good I find 4 things bad said... Set my mind at ease please...



Mine hasn't needed any adjustments yet. It's always right where it should be. I left it stock. I had the same worries reading they are lean from the factory. I strapped a big bar on it and buried it in some wood. I ran maybe 2 gallons thru it cutting firewood before I milled with it. Keep your chain sharp, don't run it with the brake on, listen to it. It'll tell you something is wrong. shut it off and figure out what it is. I broke a clutch spring the first week I had it. I only fill up a gallon can and only use it for a week then I dump it in my truck and start over. Seriously it's a saw, eventually it's gonna break, they all do. Some more then others. Watch Brads video on tuning in the wood. Most issues are from not paying attention.


----------



## jaycky

Alright good I'm gonna take and the 661 out shortly with smaller bar and chop wood with it for break in. After that will then hook up to mill.


----------



## betterbuilt

jaycky said:


> Alright good I'm gonna take and the 661 out shortly with smaller bar and chop wood with it for break in. After that will then hook up to mill.


I usually run 50-1 for firewood and 40-1 for milling. Watch brads video on tuning. listen for that blubber and if it not doing it you need to tune it. 661 is an auto tune. I haven't heard of anyone milling with it yet. You may be the first.


----------



## jaycky

I will be tuning this saw regularly I think just for keeping my mind at ease.
I have that premix from stihl that I have in all my saws while not in use 50:1 so firewood and break in for the first 14 tanks.


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## Rx7man

Did anyone look at that link I posted? While it's true that more oil in the mix leans out the fuel mixture, if you're that close to the bleeding edge of being lean, you're going to be cooking the engine anyhow... Going from a 50:1 mix (2%) to a 32:1 mix (3.1%) is just over 1% change... It's equivalent to less that 1000 ft elevation drop,... Looking at air/fuel ratios, you have a 'perfect' ratio at about 14:1, but make most power around 12.5:1, and many turbo vehicles will run as low as 11:1 for the cooling effect of the fuel. 
Certainly it's possible for extra oil to push it over the brink.
Engines need a certain amount of oil, and a certain amount of fuel,.. the problem is they're getting both at once, so if you lean the saw out you're starving it for oil at the same time when you're running a 50:1 mix. A second problem with not running sufficient oil through the engine is the reduced piston sealing, and that means hot combustion gases go by the piston and rings, and heat them.
From that link, they did a dyno test on a 125cc dirt bike engine.., and jetted it properly for each oil mix


> We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.
> 
> Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.



I can say I noticed a significant increase in power in my stock saws when I increased the oil from 40:1 to 30:1.. And since a milling saw is working a long time at full throttle in a single cut, I think it would benefit it.


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## JS929

BobL said:


> In analysing the circumstance I'd be asking myself the following
> How does a bar get pinched when milling?
> What type of wood were you cutting?
> How long had it been since the chain was sharpened?
> What fuel/lube mix are you running?
> How many RPM below max have you got the H screw set at ?
> How much pushing was happening?
> 
> Fear of this is what leads me to this.
> 
> 
> 
> 
> 
> 
> I reckon your cylinder is salvageable.



Those are the exact same series of questions that I asked. I want to know how the bar got stuck milling. I'm not saying it isn't possible, but I have never done it unless the wedges slip out and I go to remove the saw from between the slab and cant.


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