Stihl ms291 help

[jerryok]

Hello all, I have a ms 291 that’s bogging down and sputtering when I’m running it full throttle. When I back off it seems to stop sputtering. I’m running stihl mottomix in it and changed the fuel filter. Spark plug looks chocolate brown so I think that’s good. Any ideas would be greatly appreciated . Gerry

 

[HarleyT]

Have you gone through the carb?

 

[jerryok]

Gonna try that next thanks

 

[066blaster]

Take the screen out of the muffler, do a muffler mod. Make sure air filter is clean.

 

[066blaster]

My saws seem to run best on 87 octane. just my observation. I tried race gas once and my 066 wouldn't even run on it. ms 290 ran rich and air filter was soaked with gas.

 

[toadman]

Mine often does this above 6k feet elevation... check carb settings. I found its because it is getting too much fuel for the amount of air it can pull in.
Also, the factory air filter gets plugged after a while. It doesn't always look as filthy as it is, so I generally Scrub it gently with a stiff toothbrush every few days of cutting. Either one will cause the saw to bog and run awful in the cut as you described.

 

[jerryok]

Thanks guys for the help. Carb was good Harly T . Toadman it ended up being the air filter. Thanks! When I opened the cover it looked good so I didn’t think it was that. When I took it off and scrubbed it a lot of gunk and dust came out and she’s back to running fine. Guess I shouldn’t overlook the easy things first. 066blaster will look into doing that muffler mod.

 

[jerryok]

Sorry 066blaster didn’t see you told me to check the air filter. My bad.