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Discussion Starter · #1 ·
FYI - I'm a weekend warrior, basics only...
Have a small Stihl chainsaw that instantly bogs when hit full throttle from idle. Will actually stall out if I stay on full throttle... I put a new carb on and same issue...
I noticed that if I cover the air intake hole completely with thumb it does not bog until full rpm. Release my thumb and it runs full rpm, but goes back to bogs from idle....
I adjusted the "H" screw a bit and seems better but would like to understand the root cause...
Any ideas would be much appreciated....
Saw is only couple years old. Fresh gas, new plug, appears to be no air leaks around intake box...
Thanks
Bob
 

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Welcome Bob. i moved you to chainsaws. I'll try to conjure up our chainsaw expert paging @WrongDoug
 

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It is usually a lean L jet that causes bogging on throttle advance. H jet richness should be adjusted until runs a little rough on WOT no load but then smooths out under load.
 

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Discussion Starter · #4 ·
It is usually a lean L jet that causes bogging on throttle advance. H jet richness should be adjusted until runs a little rough on WOT no load but then smooths out under load.
Is there a good step by step procedure you use to adjust all 3 screws? I've seen a few on YouTube but would like more info.
 

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I've been doing this for over 50 years, long before YouTube, so have never had to probe that resource. Basically richen up the L jet until it stops bogging and richen the H jet until it runs a little rough at WOT no load. Then adjust the idle so it doesn't stall but not so fast that the chain moves.
 

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Discussion Starter · #6 ·
I've been doing this for over 50 years, long before YouTube, so have never had to probe that resource. Basically richen up the L jet until it stops bogging and richen the H jet until it runs a little rough at WOT no load. Then adjust the idle so it doesn't stall but not so fast that the chain moves.
Where is the starting point for the screws before this procedure?
 

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1 & 1/2 full turns from all the way in. Turning it in makes it leaner. Turning it out makes it richer.
 

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Also does the saw have limiter caps on the adjustment screws?
 

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Discussion Starter · #12 ·
Aftermarket carb was put on, original carb was doing the exact same thing....
Yes, the carb has limiter caps.
 

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Aftermarket carb was put on, original carb was doing the exact same thing....
Yes, the carb has limiter caps.
Get rid of the aftermarket carb. Seriously, they aren't worth their weight in plastic. Buy a rebuild kit for the OEM carb and go from there.
 

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It’s also worth inspecting the fuel lines. Sometimes they start to fall apart and don’t deliver enough fuel. I have also had the filter fall off inside the tank and then the pick up doesn’t pull reliable fuel.


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