Chainsaw idles bad, long throttle response time

rubydog

rubydog

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Jul 12, 2021
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My chainsaw, (a ryobi pcn4040) is having some issues. the fuel lines were worn out, so i replaced them and put the saw back together. when i started the saw, it would only run for a few seconds, and run at full throttle for no reason. i tried adjusting the low and high speed screws, to no avail. i took the carby off and found lots of gunk, so i cleaned the carby and re-assembled the saw. now, it is holding idle. However its idle is erratic, changing speeds constantly, and also the throttle response time is very bad. (i will pull in the throttle, it takes a good 3-4 seconds to rev up fully, then when i release the throttle it will very slowly rev down. i have tried adjusting the screws again, but i cant get it to run right. any ideas?
thanks
 
Westboastfaller

Westboastfaller

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In short of buying a new carb, I suspect it needs a soak due to inner build-up.
Friend would use a real strong brake cleaner & drop it in a coffee can with lid on for 24h.
Strip it down the best you can.
Can't leave any plastics or anything like that or it will eat it.
The good stuff would actually bleach out the metal when you got them back. Other stuff he used needed a three day soak to do anything.
 
rubydog

rubydog

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thanks for the replies, i will try cleaning the carb as you described. i also forgot to mention that the primer bulb only fills up about half way with fuel, does this mean much?
 
Okie294life

Okie294life

Small engine jackwagen.
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Arkansas
thanks for the replies, i will try cleaning the carb as you described. i also forgot to mention that the primer bulb only fills up about half way with fuel, does this mean much?
Late to jump in but it sounds like the screen in the carb is clogged up. Unless you are good at rebuilding carbs I’d recommend getting another carb. Most of the newer stuff that’s out there isnt rebuildable…..it’s a trend. If it’s not the screen that’s the issue the jets are probably gummed up and if the carbs one of those rotary valve carbs or one that has the needles locked in for H&L speed jet….you’re out of luck.
 

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