Troubleshooting: Stihl saw won't idle (dies)
I've been troubleshooting an idle problem with a Stihl saw (TS-400 cutoff saw) and I'm nearly out of ideas. Hoping someone here can help. I feel invested now and don't want to simply hand it over to the service department.
By the way, I bought this saw used, so I don't know anything about its history.
The saw runs fine at higher speeds, but if I try to let it throttle down it dies immediately below a certain rpm. It also hesitates when I throttle up (does not accelerate responsively -- may actually drop a little for a half-second).
Making sure the saw is well warmed up does not help.
It was interesting that earlier, I could adjust the saw so that it would idle for a little while (less than a minute). Trying to solve that, I disassembled the carburetor, gave it a dip treatment, and reassembled with a full carb rebuild kit. I also adjusted (bent down) an inlet control lever ever so slightly to sit flush with the carb chamber floor, just as it is supposed to. But afterwards the idle performance was actually worse, and no carb adjustment corrected that.
I disassembled the carb and bent the inlet control lever the other way a bit, but that had little if any effect.
The saw passes all 3 vacuum and pressure leakage tests for the carb and crankcase.
The spark plug was replaced not long before I got serious about solving this.
- a fuel hose
- in-tank fuel filter
- auxiliary air filter
- spark arrest screen
- exhaust gasket
- decompression valve (lets the Stihl start easier with less kick-back)