Thread: Stihl brushcutter problems

Sounds like the mixture has changed slightly and may be running a tad rich. You should find 2 screws on the carby - marked hi and lo. I'd start by screwing in the hi screw a touch while holding the throttle open to see if it responds better. There are some good on line tutorials on how to tune a 2 stroke engine. Ill see if I can find one I used last time - it worked for me on an old chainsaw I was playing with.

i concur, play with the high needle a bit.
good luck

Tried playing with the mixtures, they were wound right up and didnt help the situation when I turned them down....

I agree with it being the mixtures, but I found it virtually impossible to tune my stihl km90r & ended up taking to an expert. Well worth the expense IMHO

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Try taking the muffler off and checking for clogs. Then look at the exhaust port on the motor. Sometimes they get gummed up with soot and will cause all sorts of bogging.....


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Does it have the one piece fuel delivery/return black rubber tubing?.
I had the same issues with mine. Turned out to be a perished fuel delivery tube making the mixture too lean. I ended up just using some aquarium air tubing to replace the inlet/return and have not had an issue since. I was a little dubious about the compatibility of the tubing with fuel but so far, all good.
Regards
Robbo

The one way air inlet valve on the filler cap may be too tight, rubber gone a bit hard. Unscrew the cap for a second while its bogging down and see if it picks up. I had this problem with a new brush cutter recently, I stuck a sharp knife in the valve and reduced its tightness a bit. Works perfectly now.

mud wasps got into the muffler on mine and made it bog down and hard to start.
Don.