For some unknown reason the idle speed on my Husky 137 chainsaw has suddenly increased. I had it adjusted just perfectly and it ran that way for several years. Now it has suddenly increased to the point where the chain spins pretty fast.
Is it just a matter of readjusting the idle speed? Or could it be that a piece of dirt has partially blocked the carburetor? Last fall it speeded up but after I ran it for about 15 minutes it idled back down by itself. I just ran it for another 15 minutes and it didn't slow down this time.
I ran it dry last fall but it's got plenty of gas now.
I'm kind of concerned that it might have a particle blocking the flow of gas and causing it to run lean. But would that necessarily make it run fast on idle? And would it go away after running it for 15 minutes like it did last fall?
I had a 16 hp Johnson snowmobile and one night it leaned out. I could keep up with the neighbors 500 TX Polaris for a few hours but then it got slower and slower. We ended up replacing one of the cylinders.
I would pull the plug and have a close look and see if it's burned the plug, replace it if in any doubt, check the fuel supply line, if you can blow everything out with air (carefully) and really clean everything up and make sure the linkage etc are all clear and not binding or filled with dirt etc.
I would also suggest buying a can of Husky Pre-mix which is not only mixed 94 octane & 50:1 oil but it has a conditioner in it. You'll also know that the gas is good (apparently there has been a few not so great batches of gas hit the market).
Even though there is a spring on the idle screw, these buggers vibrate like hell and after a while it can dial out as a result. The spring can be replaced (get the right one for the job) also check the carb screws etc to make sure everything is still tight, maybe sucking a bit of air in. I only say that because you say once heated up it (15 min run) it goes back to good idle.
One thing people with two strokes should learn to do is read the plug color. A good running 2 stroke with a perfectly adjusted carb the color of the plug should look like a nice cup of cofffe with cream.
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