Stihl 021 chainsaw dies at high revs

[dorset972]

My usually trusty Stihl chainsaw has now started to die when run at high revs. It starts and idles OK but revs just die off when cutting. Air filter is clean and plug is OK. Looks like I may be getting some exercise with the bowsaw!!!
Any suggestions gratefully received.

 

[TicklyT]

An easy one to start the ball rolling - check the fuel tank vent, usually in the filler cap. If it gets blocked, the fuel can't get out of the tank and into the carb. fast enough.

 

[foxhole]

Empty and refill fuel, wrong oil mix also gives those syptoms.

 

[Burnerman]

If there are 2 adjustment screws on the carb, turn the one marked 'H' 1/4 turn anticlockwise.
If that doesn't make any difference, a carb strip plus a diaphragm / gasket set is a good idea.
John

 

[dorset972]

Thanks for all suggestions. I have ruled out the fuel mix and will try the other suggestions and let you know.
Thanks again.

 

[igotalake]

any joy Dorset?

 

[dorset972]

Yes. It was the venting on the tank. When I removed and then replaced the filler cap, the engine ran OK and then started to die after about a minute. I have cleaned the vent tube and all is OK. Thanks igotalake, your post reminded me to get it fixed. Thanks also to all other suggestions, in particular tickly T: spot on mate!

 

[igotalake]

i will try that with mine then...

cheers,

john.

 

[igotalake]

very late addition:
mine was down to some crap collected in the carb in a little metal gauze plug, called a 'welch plug' i think. it requires the removal of carb and then carefully take the bottom/top off where the needle valve is, if i remember rightly. you've got to pretty delicate getting the gauze plug out unless you get a carb service kit which should have a new one in.