What Am I Doing Wrong!!!!!!

[John W Foster]

Hello All:

In the last 5 years I have had 3 saws die on me as a result of scored pistons and cylinders. Two were Husqvarna ( one an XP) and the latest a Stihl 291 that was barely a month old. The 291 had only ever seem premium gas and had only Stihl oil mixed with the gas. We always run the saws at full throttle when cutting. We use them for cutting firewood for our own use so it is not like they are being run 24/7. The curious thing is that my old Husqvarna 353 which is probably 10-15 years old keeps chugging along and has never needed major repair, it does the same work and burns the same fuel as the other saws do. Does anyone have any ideas?

Thanks
John

 

[ATpro]

Sounds like you are running them to lean, maybe not enough on the oil mix, I run a 40:1 mix. First thing I do is pull the limiter caps off and readjust the carb for a richer flow. I try to stay away from the crap you can't control they put on saws these days.

 

[Swanman]

Hello All:

In the last 5 years I have had 3 saws die on me as a result of scored pistons and cylinders. Two were Husqvarna ( one an XP) and the latest a Stihl 291 that was barely a month old. The 291 had only ever seem premium gas and had only Stihl oil mixed with the gas. We always run the saws at full throttle when cutting. We use them for cutting firewood for our own use so it is not like they are being run 24/7. The curious thing is that my old Husqvarna 353 which is probably 10-15 years old keeps chugging along and has never needed major repair, it does the same work and burns the same fuel as the other saws do. Does anyone have any ideas?

Thanks
John

Are you getting dirt and grit past the air filter?

 

[John W Foster]

Are you getting dirt and grit past the air filter?

I always use OEM air filters and I believe them to be correctly mounted.

 

[Bob Hedgecutter]

Photographs will speak volumes.
Of the removed pistons, the saws and the bar/chains.
Could be one single thing- could be a combination of unfriendly circumstances.

 

[Philbert]

STIHL, ECHO, etc., have ‘Failure Analysis Manuals’ that go into great detail on this, with detailed photographs.

Your dealer may have access to these.

Philbert

 

[ZeroJunk]

Take the MS291 back to the dealer and demand a warranty repair.

If they hesitate call Stihl directly.

 

[lone wolf]

Take the MS291 back to the dealer and demand a warranty repair.

If they hesitate call Stihl directly.

I don't know, you think STIHL will get involved or what?

 

[John W Foster]

Take the MS291 back to the dealer and demand a warranty repair.

If they hesitate call Stihl directly.

I am expecting warranty repair. After all, the saw should be set up properly at the time of sale.

 

[farmer steve]

I don't know, you think STIHL will get involved or what?

I've seen a few threads here over the years where someone went to the "top" and got better results.

 

[ZeroJunk]

I don't know, you think STIHL will get involved or what?

I would. So far, they do not check behind us.

 

[ballisticdoughnut]

I would absolutely pursue a warranty claim on the 291. The dealer should be adjusting the carb before it leaves the store, they run too lean out of the box. I just sold a 291 not ten minutes ago. Opened up the high speed almost 1/2 turn and low speed about 1/4 turn. Bumped the idle speed up as well. We adjust every single new two stroke machine that goes out the door.

 

[pro94lt]

post a picture of the chains...

 

[knoxman]

I got a lot of good advice on my recent MS291 scoring case; https://www.arboristsite.com/threads/ms291-cracked-piston.371479

From my recent learning causes of overheating in the MS291 can be:
- dull chain or improperly set chain rakers causing saw to rev too high and overheat
- carb settings too lean (strato carb tendency with ms291)
- leak sucking air causing lean condition and overheating
- improperly mixed fuel or too lean fuel to oil mixture: try 40:1
- water in fuel

 

[stihltech]

You can only get an answer if you take it back. Or tear it down yourself, but why would you do that?
Stihl is fair with us as long as we are fair to them. Need a diagnosis first.

 

[ZeroJunk]

We have a couple of card board boxes full of top ends and complete four mix engines in case Stihl ever wants to come and inspect. They never have.

If they have an issue they know it. If they don't have an issue they know it.

I would. So far, they do not check behind us.

I should rephrase that. We have to send it in for approval. But, if they approve it that's the end of it.

 

[NSEric]

The newer strato style saws dont like being worked hard if they're set a touch lean and running 50:1.
It's not just one thing it's a combination of all 3 things.
If you set the carb a little rich they last fine or if you run 32:1 they will last, doing a muffler mod to get rid of heat helps too.
Older saws are just tougher, they dont have strato ports so they get more gas/lube, the mufflers are more open so they dont get as hot and they're generally set a little richer keeping them cooler. This is why your 353 is still going.

 

[Bob Hedgecutter]

The newer strato style saws dont like being worked hard if they're set a touch lean and running 50:1.
It's not just one thing it's a combination of all 3 things.
If you set the carb a little rich they last fine or if you run 32:1 they will last, doing a muffler mod to get rid of heat helps too.
Older saws are just tougher, they dont have strato ports so they get more gas/lube, the mufflers are more open so they dont get as hot and they're generally set a little richer keeping them cooler. This is why your 353 is still going.

Which is exactly why I asked for photos back in post #5- but we have no further information since.

 

[stihltech]

I love the over the internet, no pictures, magic wand diagnosis.

 

[HarleyT]

For the record, this is the carb for the ms291.