Stihl MS880 runs at high idle then dies.

[chad556]

first question is are you in tree cutting business?

replace p/c, fuel line, fuel filter at very least.

how did the neighbors like the saw running in apt? lol

Haha, Actually I'm in the golf course business which means I only cut trees when theres no grass to cut. Actually this year we took out some big oaks and other species and i want to try my hand at milling so I'm trying to get that 880 running.

Oh, and my neighbors probably think im crazy, not everyday you see a guy trying to start up a 120cc saw, especially in a neighborhood where the tallest tree in sight is a 15' callary pear

 

[chad556]

In post #10, the picture of the carb you can see the remains of the black gasket on the top cover. Was the gasket there when you tore down the carb? If not you could be sucking air just like a bad impulse hose would. Definatley read up pressure and vac testing.

Good eye, didnt even notice that, it sure looks like there should be a gasket there. I certainly didn't lose it, must not have been there. So I need a carb rebuild kit too? Any ideas where to find one? also, I'm having a hard time finding a good instructional pressure/vac test video/picture thread so if anyone can point me in the right direction i would appreciate it.

 

[josh1981]

Haha, Actually I'm in the golf course business which means I only cut trees when theres no grass to cut. Actually this year we took out some big oaks and other species and i want to try my hand at milling so I'm trying to get that 880 running.

Oh, and my neighbors probably think im crazy, not everyday you see a guy trying to start up a 120cc saw, especially in a neighborhood where the tallest tree in sight is a 15' callary pear

Do you do it by yourself? if so how did you get started? Golf course? lawn maint?

Well I live in a townhome my neighbor had a small craftsman saw. Actually most people in my area only use small homeowner HD saws or small stihl... And I have a 066 361 211 yes my neighbors think im crazy... but I cut firewood in winter. and storms around here can get rerally bad. $$$$ if big tree falls!

Oh I saw that staten island storm on youtube last year I think? Mayor was on there and showed one guy cutting with a stihl saw. Hope everyone was ok in that.

About your saw how is the carb and is muffler screen plugged up?

 

[mtngun]

Good eye, didnt even notice that, it sure looks like there should be a gasket there. I certainly didn't lose it, must not have been there. So I need a carb rebuild kit too? Any ideas where to find one? also, I'm having a hard time finding a good instructional pressure/vac test video/picture thread so if anyone can point me in the right direction i would appreciate it.

Carb kit is always good insurance and they don't cost much. You can either order it from a Stihl dealer, or, once you determine the kit # by looking up the carb info on the carb manufacturer's website, you can get it on the 'bay or from an AS sponsor like Bailey's.

Here's one thread on vacuum testing. Pressure testing works the same way except you need a pressure source -- only a few psi so as not to damage anything. If it passes the vac test, you're probably good to go. If it flunks the vac test, a pressure test can help pinpoint the leak. Some people like to do both tests just to be safe.

http://www.arboristsite.com/chainsaw/42768.htm

 

[chad556]

Do you do it by yourself? if so how did you get started? Golf course? lawn maint?

Well I live in a townhome my neighbor had a small craftsman saw. Actually most people in my area only use small homeowner HD saws or small stihl... And I have a 066 361 211 yes my neighbors think im crazy... but I cut firewood in winter. and storms around here can get rerally bad. $$$$ if big tree falls!

Oh I saw that staten island storm on youtube last year I think? Mayor was on there and showed one guy cutting with a stihl saw. Hope everyone was ok in that.

About your saw how is the carb and is muffler screen plugged up?

No, nothing quite as fancy as that, I have a bachelors degree in golf course management and I work as an assistant superintendent at a private club.

Oh and I think I remember that strom, it was the first week I moved down to SI about a year ago, huge mess, lots of lost power, blow downs, flooding. It made for an interesting first couple weeks on the golf course. Lots of raking.

As for the saw I think I am going to find out what I need and rebuild the carb just to be safe, as far as the muffler screen, I took it out and will probably leave it out unless there is a really good reason to have one?

Also thanks for the link to the Vac test tutorial mtngun. Seems like every time i search for something i find tons of interesting threads but not the one i need lol. I am going to harbor freight tomorrow to pick up that break bleeder kit and see if i can do a vac test. My piston kit came in the mail so thats all ready to go. My muriatic acid is coming soon so i can clean up the cylinder. Thats a lot of crap to buy but its way cheaper than going to the dealer, plus i'm getting the invaluable experience.

One more question: If i do the pressure test I need the flywheel and clutch removed so i can test the crank seals, correct? are there any other areas I should test or that i would need to access? Thanks

 

[Andyshine77]

Check the crank seals, cylinder base gasket, carb intake boot, impulse line and fuel line. That's all I can think of at this hour.

First determine that you do have an air leak with a pressure and vacuum test. If you do in fact have an air leak, yes remove the flywheel and clutch then spray down everything with soapy water. With the case under pressure any leak will produce lots of bubbles.

 

[chad556]

More pictures

Ok so I got my vac tester today and did my best to use bike tubing to seal the case. I kept having no luck with the muffler because it clamps on and its not designed to have a gasket so I made a piece of rubber for the outlet of the muffler (formerly where the spark arrester screen was) and that worked out ok I think. I pumped it up and no matter how fast I pumped I couldnt get it past 5 inHg on the gauge. Not sure where the leak was but strongly suspecting the gasketless muffler I tried to do a pressure test. In the process of removing the clutch and the flywheel I got my little rope jammed into the exhaust port. Long story short, I had to remove the cylinder so I decided to take the whole thing apart and take a look at what was going on. Here is what i found:

How does this look to you guys? Is it worth trying to salvage the cylinder? It doesnt look so bad to me but then again this is my first time really getting my hands dirty with this stuff.

Also I still have not gotten my flywheel off, I'm going to just keep tapping away at it but if anyone can give me a better way i would love to hear it.

 

[mtngun]

Thanks for the great pics.

I have never seen anything quite like it, so I'm hoping someone else will chime in.

That almost looks like a crack running between the exhaust port and the upper transfer ? Weird, anyway.

It's great to take the jug off to see the damage, but now you can't leak test it, and you still do need to leak test it. Dunno what to tell you about the 880's unique muffler attachment. If it's not holding vacuum, the next step is to apply a few psi pressure (easier said than done, you'll need a source of of low pressure air) and find out where it is leaking. Should be able to hear it hiss and/or spray soapy water and look for bubbles.

 

[mtngun]

Regarding flywheel removal, a special puller is required, don't try to hammer or pry it off or you'll end up breaking it.

 

[RiverRat2]

Just looking I think You cylinder is going to be fine,,, Can you hang a finger nail in any of the grooves or aluminum deposits??? You will Know better after you remove the aluminum transfer,,, Ive got an 066 that I put a Meteor piston in 3 years ago that looked worst than that,,, it makes 165 psi. compression and is bad to the bone!!!! Make sure the impulse hose is in good shape... It sounds like an air leak to me from your description and watching the vid,,,

Good luck!!!

 

[chad556]

There is a little bit of a fingernail hang up on some of the rougher spots. I am hoping that that turns out to be mostly aluminum from the piston but I wont know for sure until I clean it up with my acid (once it gets here). All I can do now is wait until i get the acid (i'll be sure to post an 'after' pic), then clean up the cylinder, install my new piston, pop off my flywheel and pressure test my seals and gaskets, rebuild the carb, then put it all back together, slap on the new bar and let her rip.

I have a pretty good assortment of pullers and related tools at my disposal at work to get that flywheel off (im not going to bang on it anymore than i have, the thing is plastic after all), also our mechanic is going to be back from his vacation so hopefully he will help me figure it all out on Monday. Thanks for all the help and advice so far and don't worry, I will keep you posted on my progress of getting this beast running again.

 

[mtngun]

I have a pretty good assortment of pullers and related tools at my disposal at work to get that flywheel off (im not going to bang on it anymore than i have, the thing is plastic after all), also our mechanic is going to be back from his vacation so hopefully he will help me figure it all out on Monday.

It requires a threaded puller. You can either get it from Stihl, or get a generic one that is used for mopeds. Can't remember the thread sizes off the top of my head.

In any event, you don't need to pull the flywheel to do a vac test, only if you suspect a leak on the flywheel side seal. Figure out a way to seal the muffler, bolt the jug back on (no need to install rings, etc) and figure out where the leak is.

 

[josh1981]

thats cool. good money.

leave the spark screen in there. its there to prevent sparks from flying out causing fires. could get ion major trouble.

good luck on rebuild.

No, nothing quite as fancy as that, I have a bachelors degree in golf course management and I work as an assistant superintendent at a private club.

Oh and I think I remember that strom, it was the first week I moved down to SI about a year ago, huge mess, lots of lost power, blow downs, flooding. It made for an interesting first couple weeks on the golf course. Lots of raking.

As for the saw I think I am going to find out what I need and rebuild the carb just to be safe, as far as the muffler screen, I took it out and will probably leave it out unless there is a really good reason to have one?

Also thanks for the link to the Vac test tutorial mtngun. Seems like every time i search for something i find tons of interesting threads but not the one i need lol. I am going to harbor freight tomorrow to pick up that break bleeder kit and see if i can do a vac test. My piston kit came in the mail so thats all ready to go. My muriatic acid is coming soon so i can clean up the cylinder. Thats a lot of crap to buy but its way cheaper than going to the dealer, plus i'm getting the invaluable experience.

One more question: If i do the pressure test I need the flywheel and clutch removed so i can test the crank seals, correct? are there any other areas I should test or that i would need to access? Thanks

 

[chad556]

Ok so I put my jug back on this morning and tried to seal up the muffler again, I found out there is a muffler gasket it was just stuck to the cylinder. I had a hard time getting the muffler to seal but i finally got a piece of inner tube in there and did a vac test, i pumped the gauge up to 5 in-Hg and about 15 minutes later it has only dropped about a quarter of an in-Hg on the gauge. This would be passing correct? Im not too sure where to go from here but i guess i just proceed with the rebuild? what other ways can a piston get scored like that? Bad carb adjustment, hard use, straight gas/bad mix? I think I can rule out air leak.

 

[splitpost]

Ok so I put my jug back on this morning and tried to seal up the muffler again, I found out there is a muffler gasket it was just stuck to the cylinder. I had a hard time getting the muffler to seal but i finally got a piece of inner tube in there and did a vac test, i pumped the gauge up to 5 in-Hg and about 15 minutes later it has only dropped about a quarter of an in-Hg on the gauge. This would be passing correct? Im not too sure where to go from here but i guess i just proceed with the rebuild? what other ways can a piston get scored like that? Bad carb adjustment, hard use, straight gas/bad mix? I think I can rule out air leak.

sometimes a vac test won't pic up a leak ,thats when you need to do a pressure test to be sure

 

[mtngun]

Your vac test sounds good.

There's still the fuel line, fuel filter, and carb to investigate.

I still haven't figured out the unusual wear pattern on the jug. :msp_confused: I'm hoping someone will come along and say "hey, I've seen something like that before and here's what caused it."

 

[chad556]

sometimes a vac test won't pic up a leak ,thats when you need to do a pressure test to be sure

I'm a step ahead of you there, before I took all the seals i made out I put about 10 lbs of pressure in there and sprayed the thing down repeatedly with soapy water. It held the pressure and the only bubbles I got were a couple coming from the muffler where my little inner tube couldnt hold on. No other bubbles or tell tale hisses

Also mtngun, Thanks for the advice im going to remove the impulse and fuel lines just to get a good look at them and replace if necessary. After hunting endlessly for a carb kit i found one for an 084 carby that looks like it will have most of what I need, some of the gaskets on my carb look iffy (stiff and crumbly) so I'm going to rebuild it and see. From everything I have seen so far I think the carb is the best candidate for the saw running lean. I am guessing the carb started to fail and the previous owner just kept running it, hence the damage. Sounds like a reasonable cause and effect right? I mean, it could have happened that way right?

Anyway, just waiting on my acid on monday to clean up the cylinder and then my bar chain and carb kit will come at the end of next week, get all that together and I think I will be good to go.

 

[CTYank]

Ok so I put my jug back on this morning and tried to seal up the muffler again, I found out there is a muffler gasket it was just stuck to the cylinder. I had a hard time getting the muffler to seal but i finally got a piece of inner tube in there and did a vac test, i pumped the gauge up to 5 in-Hg and about 15 minutes later it has only dropped about a quarter of an in-Hg on the gauge. This would be passing correct? Im not too sure where to go from here but i guess i just proceed with the rebuild? what other ways can a piston get scored like that? Bad carb adjustment, hard use, straight gas/bad mix? I think I can rule out air leak.

Mind you, I'm no expert in this, but it seems that your test pressure is way low. Reference I have ("Two-Stroke Engine Repair & Maintenance" by Paul Dempsey, McGraw-Hill 2010) recommends drawing down crankcase to 7 psig vac.) 5" Hg would be only about 2 psig. Dempsey further says "If pressure remains constant, or increases by no more than 4.5 psi over 20 seconds, the seals should be okay." (BTW, the book is very helpful in understanding 2-strokes.)

For pressure-testing, his recommended source is 7 psig and no more.

HTH. Regards.

 

[RiverRat2]

Chad Would you like a copy of the service Manual for an 088??? It should work for your saw and has a detailed description for leakage testing both pressure and vacumn and all the tolerances,,,

What about the IPL for the MS880????It shows the exploded view and has all the part #'s

PM me your Email Addy I would be glad to send them 2 ya

Also On my salvaged 066 I mentioned earlier it looked way worse and cleaned up real good used the muratic acid directly on the aluminum X-fer with a long Q-tip let it work a few mins then use fine emmory to polisih and clean,,, It had a few verticle lines you could see but a fingernal wouldnt hang,,, they will fill in with carbon and actually seal up pretty well.... I used a Silicone Carbide Ball hone to refresh the Cross hatching very lightly and of course ported the cylinder and piston windows and let it rip!!!!!!!!!

 

[Andyshine77]

If she held pressure like you said it doesn't have a leak. I know a few people that had 088/880's that scuffed the piston and cylinder like yours. I think it's a combination of a few things, not just one big issue, like an air leak. Tuned lean, tight cold bore, bad fuel/oil, then running the saw with a dull ass chain. All of these things will make a new $1,600 880 worth $650 in a hurry.