Well I have been working with my dealer and we are making some headway....finally. My issues always start as the temperature starts getting higher above about 85 degrees and especially at higher elevations. Hard to get started, usually 8-10 pulls, dies constantly while waiting for it to acclimate, and also dies upon throttle chop. Sometimes will just stumble and die while in the middle of a cut too. It works fine below about seven thousand feet in elevation even when hot out, but add in some elevation and all bets are off.
Saw is in its third season and has about 100 hours on it, good compression, well taken care of.
To my dealers credit they are working with me as they also want to know what is going on. I been working on saws, lawnmowers, small engines, and especially motorcycles for 50 years and am real good at problem solving, or at least was till I got started on this issue!
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First I replaced the solenoid, and went through the carb, no change, then my dealer took it went through the carb, replaced the solenoid as well as the diaphragm, and talked me into using the $tihl premix. STILL no change.
Next replaced the control unit (coil) and that made it start a little better but still hard to accelerate and stumbles and dies frequently.
Put the original coil back in and installed a brand new carb. Now it starts up with one or two pulls, idles good and long enough to acclimate with no issues, but is still stumbling a little upon acceleration and dying about 30% of the time when the throttle is released.
Now thinking it might possibly be a combination of control unit AND carb? Could I be THAT lucky?
STILL do not understand what could be going wrong in the carb as have had it apart and under a microscope a couple times checking everything out and all looks good.
I would like to know if anybody has ever seen schematics on one of these carbs or can answer a question? At the bottom of the hole where the solenoid fits in there are two small holes, one goes to a little piece pressed into the throat of the carb that I believe is probably a one way valve, possibly a ball check type. The other little hole is in a small round piece of brass that is pressed into the casting at the bottom of the hole. It has a real small angle chamfer around the top of the hole, but I cannot figure out where that little hole leads. Any ideas?
Now going to put the new control unit back on as well as leave the new carb on it and see what happens next time I head to the hills.