What Am I Doing Wrong!!!!!!

[lone wolf]

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

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Wearing EPA handcuffs!

 

[HarleyT]

With no pics, it is silly to say much.

 

[ZeroJunk]

Wearing EPA handcuffs!

You can adjust those things with a little hex driver until you push that insert in when they come as a part.

 

[capejwc]

Let it warm up a little before starting to cut. Sounds like you are having some cold start scoring and possibly running too lean.

 

[Philbert]

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

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Looks more like a motor for a small drone!

Philbert

 

[lone wolf]

You can adjust those things with a little hex driver until you push that insert in when they come as a part.

What is it a 4mm hex?

 

[SteveSr]

What is it a 4mm hex?

2mm hex. It is designed to bend/break a 2mm driver if you try to adjust it with the caps in place. So you have to carefully remove the caps and then reinstall them in "factory" position, do your adjusting and then push the caps home.

 

[Seachaser]

Let it warm up a little before starting to cut. Sounds like you are having some cold start scoring and possibly running too lean.

That was my first guess. I try to let mine warm up a minute and cool down a minute.

 

[John W Foster]

Sorry about the no pictures, but the saw is in at the dealer's shop so I can't get pictures.

 

[ZeroJunk]

What is it a 4mm hex?

Even if it is pushed in you can disable it with the correct Stihl tool and pop it back out.

Personally. I never see new equipment that is sold. So, it goes out the way the factory set it.

I don't think it is like every piece of equipment is too lean, because they certainly don't all come back.
If somebody brings a saw back and think it is too lean we can remedy that. Did one the other day.

 

[Tony Mayhew]

NSEric hit it right in the bullseye with the diagnosis of muffler being the culprit of scored piston half the time. The muffler/exaust pipe on all these newer saws are way to restrictive and collect heat with all the crap like Baffles, spark arrestors, and blunt faces the heat runs into before direction changes to end up exiting out of a tiny hole such as the screw in spark arrestor that stihl uses on some of their equipment. It collects heat that gets transferred back into the cylinder and creates way too much heat and things go down hill from there.

 

[Lightning Performance]

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

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POS is what you have there.
Looks just like the sad 201T carb.

 

[stihltech]

Man- I wish I could diagnose like this at the shop! I can't speak for your dealer, but there is a procedure. No magic wand. The piston usually tells the story. The pressure and vacuum test may tell the cause. WAY to many variables to diagnose here without pictures.

 

[Lightning Performance]

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

Muffler mod them and tune.

 

[Lightning Performance]

Man- I wish I could diagnose like this at the shop! I can't speak for your dealer, but there is a procedure. No magic wand. The piston usually tells the story. The pressure and vacuum test may tell the cause. WAY to many variables to diagnose here without pictures.

He needs the brake bleeder tool now. It was already cooked. Vactest is best.

 

[huskihl]

NSEric hit it right in the bullseye with the diagnosis of muffler being the culprit of scored piston half the time. The muffler/exaust pipe on all these newer saws are way to restrictive and collect heat with all the crap like Baffles, spark arrestors, and blunt faces the heat runs into before direction changes to end up exiting out of a tiny hole such as the screw in spark arrestor that stihl uses on some of their equipment. It collects heat that gets transferred back into the cylinder and creates way too much heat and things go down hill from there.

And yet there are some mufflers with catalytic converters in them that glow red hot and the engines last fine because they are tuned for it