Ms261 slow to accelerate

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Matt Coolen

ArboristSite Operative
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Hey everyone....let me pick your brains! Just finished re-assembling an ms261. I got it with a bad crank, someone had straight gassed it, and new, uninstalled p/c of unknown (chinese) origin. So I found a good used crank, installed with new OEM seals, gaskets and OEM carb kit. After firing it up, and warming it to tune, following stihl shop manual, I have a seriously slow to rev saw. Not boggy, just really slow to wind up. Once it is about 1/3 full rpm it wakes up and goes. Took the carb back off, cleaned and blew out all orifices with compressed air and brake clean... still the same. What's next?
 
Generally ms261's won't have that instant throttle response like say a revboost 550xp. But..they can be improved, I've found dialing in the timing advance makes a very noticeable difference. But I won't put out an exeact number of degrees, its something IME you need to increase/decrease in small increments to find that sweet spot. You'll never get that light switch speed acceleration but you can really improve them over stock.
 
Generally ms261's won't have that instant throttle response like say a revboost 550xp. But..they can be improved, I've found dialing in the timing advance makes a very noticeable difference. But I won't put out an exeact number of degrees, its something IME you need to increase/decrease in small increments to find that sweet spot. You'll never get that light switch speed acceleration but you can really improve them over stock.

I have the exact same experience. A muffler mod will also help, but the timing is the real big improvement. It seems the sweet spot isn’t a big advance. 1/3 the key or even a touch less.
 
I have the exact same experience. A muffler mod will also help, but the timing is the real big improvement. It seems the sweet spot isn’t a big advance. 1/3 the key or even a touch less.
Sounds like a plan...not sure I like the idea of filing off the flywheel... but I'll try anything once!
 
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