Blow up one piston, shame on Stihl. Blow up two pistons, shame on me. Blow up three pistons...?

[pepe_silvia]

It would not idle right for one thing. You my not notice a leak at full speed. A vac test should be done on this saw before you have another meltdown. Check the spark plug it should be tan not white after a hard run. Make sure the plug is the correct one for that saw. Are you using regular grade gas or super?

92 octane.

 

[lone wolf]

Pictures of the damaged piston, a shot of each side may help diagnose the problem.

 

[pepe_silvia]

This is all I've got at the moment.

 

[BobL]

.....every tooth is identical, every raker the same, it shows in the surface finish of the boards,

I disagree that a grinder gives a better finish and that every tooth has to be identical. All that has to be approximately the same is the raker angle. That's the angle between the raker - the cutter edge and the wood. If that is the same then every cutter will take the same amount of bite and that's what keeps the chain square on the rails. I stopped worrying about cutters being the same length back in 2008.

This is my standard finish, full comp, hand filed.

 

[KiwiBro]

Yeah, but you're milling granite. But seriously, some time ago I changed my sharpening around to the raker angle notion you have mentioned before. I went so far in testing to grind cutters different lengths and rakers different heights, as long as the angle stayed the same. As long as I didn't get too crazy with it, the chain still cross cut OK. The trick now is working out how far i can push it in different woods and uses (steeper raker angles for bucking for firewood compared to felling in the same woods, for example). Thanks for the raker info. That original thread was one of AS' gems.

 

[BobL]

Yeah, but you're milling granite.

Not all the time
I can make the finish as crappy as anyone else.
Note zig-zagging.
This is also a full chisel skip chain which is one of the hardest to get a good finish


I can't deliberately generate a good washboard but I do come across it occasionally.

 

[lone wolf]

This is all I've got at the moment.

That could be from gas with no mix or a lean seize. Got any one there that could have screwed it up? If I could see the other side of the piston I could tell more. Straight gas will do that but it could be an air leak. How is the air filter? That saw needs a rebuild and a vac test. Dont run it with out the vac test. Ship it to me and I will fix it for you if you need help.

 

[lone wolf]

This is all I've got at the moment.

http://www.madsens1.com/saw_piston_fail.htm

 

[Mad Professor]

I posted a pdf quite a while ago from husky that had pics of piston failure and causes. Lost it on my old HD when it crashed. Might be worth a search?

It does look like a lean sieze or straight gas. have also seen the same when someone saw some water in the tank and they dumped in a good portion of dry gas

 

[Timberframed]

One more thing on the oil/gas mix. The saws I use for milling are concrete demolition saws designed to run wot 24/7 25:1 manufacturer mandated. Even the tech guy over the phone said don't deviate from that. There are two labels printed on the saws 25:1. Anyway after milling Lord knows how many linear feet, inch feet, both saws still run crazy strong and periodic inspections show unscathed interiors. Just something to consider when taking a saw designed to fell/buck buck idle buck idle and make it run wot for hours.

 

[marshall]

One more thing on the oil/gas mix. The saws I use for milling are concrete demolition saws designed to run wot 24/7 25:1 manufacturer mandated. Even the tech guy over the phone said don't deviate from that. There are two labels printed on the saws 25:1. Anyway after milling Lord knows how many linear feet, inch feet, both saws still run crazy strong and periodic inspections show unscathed interiors. Just something to consider when taking a saw designed to fell/buck buck idle buck idle and make it run wot for hours. View attachment 497398

Timberframed - what manufacturer and model saw are you using? I am definately interested in any saw designed for WOT on a 24/7 basis. Thanks in advance.

 

[Timberframed]

The concrete/stone saw (ICS 633gc) is actually an Oleo Mac 999F modified however to run like a ***** ape. Reggio Emilia, Italy. I know nothing of the newer versions other than they sized down the cc's on 695, 685 and others. Alpina is also made in Italy.

 

[pepe_silvia]

The concrete/stone saw (ICS 633gc) is actually an Oleo Mac 999F modified however to run like a ***** ape. Reggio Emilia, Italy. I know nothing of the newer versions other than they sized down the cc's on 695, 685 and others. Alpina is also made in Italy.

I've seen the Stihl Rock Boss's floating around, just assumed they were MS461s at the core, with a some external features (better air filter, something to spray water on the chain, etc).

 

[marshall]

Great info - thank you. Sounds like a good enough execuse to expand the saw collection.

 

[Blisters]

Hello my name is Nate, and I'm addicted to chainsaws.

 

[BobL]

I've seen the Stihl Rock Boss's floating around, just assumed they were MS461s at the core, with a some external features (better air filter, something to spray water on the chain, etc).

They are - there's nothing special about rock cutting saws.
According to the RB manual
- same basic specs except it's 5.8 HP versus 6 HP for the straight 461. Maybe the filter has something to do with this.
- it also uses 50:1 gas/oil ratio.
- Don't forget these have no oiler. Oil is superior to water in cutting wood as it reduces resin build up and I found it also reduces B&C wear and tear.
- The other right PITA is the upright fuel cap. This means the cap is sideways when milling and if you run out of fuel while milling it is much harder to add more fuel.

Even in the Stihl manual they referred to "oil rich mix"!

 

[Grande Dog]

Howdy,
Single ended: http://leftcoastsupplies.com/?s=long+titanium&post_type=product
Double ended: http://leftcoastsupplies.com/?s=gb+double+ended&post_type=product
Regards
Gregg

 

[Streblerm]

I suspect your saw has a vacuum leak. I doubt it has anything to do with mix. It is probably a fairly small one, but under severe duty it is enough to cause your problem. I bet the leak was what caused the first meltdown. The usual suspects would be intake or crank seals. The symptom was addressed with a new P&C but not the underlying cause.

There is a ton of reading in the chainsaw forum on performing pressure/vacuum tests. The basics are seal the intake and exhaust and apply pressure/vacuum. There are all kinds of ways to do this. I usually just make block off gaskets out of inner tube for the carb and muffler and then I pump a few pounds of air through the plug hole. Then a spray of soapy water or a quick dunk in a bucket should reveal any leaks. It is a good idea to turn the crank while testing.

 

[Paragon Builder]

A saw should be tuned every time it is used and for the type of use. I keep a little orange screwdriver on me when I cut. When you learn to listen to the saw when cutting you will know when something isn't right. When milling it is more important to tune properly, but needs to be done in the cut. And a dull chain will kill your saw in heavy use as easily as a a bad tune or air leak.
If you can't wrap your head around constant tuning, buy mtronic or auto tune, then it's done for you.


Sent from my iPhone using Tapatalk

 

[lone wolf]

A saw should be tuned every time it is used and for the type of use. I keep a little orange screwdriver on me when I cut. When you learn to listen to the saw when cutting you will know when something isn't right. When milling it is more important to tune properly, but needs to be done in the cut. And a dull chain will kill your saw in heavy use as easily as a a bad tune or air leak.
If you can't wrap your head around constant tuning, buy mtronic or auto tune, then it's done for you.


Sent from my iPhone using Tapatalk

The dull chain is very overlooked as a cause.