Symptoms
- Engine dies as soon as you release the throttle
- Idle speed seems too low or erratic
- Chain moves at idle when it shouldn't (over-adjusted idle)
- Engine surges up and down at idle
Likely causes
- CommonIdle speed set too lowThe idle adjustment screw may need a slight turn to raise idle RPM.
- CommonDirty idle jet in carburetorFine passages that control idle fuel can clog with varnish from old fuel.
- PossibleAir leak at intake gasketA worn gasket lets in extra air, leaning out the idle mixture.
- PossibleDirty air filter affecting idle mixtureRestricted air changes the fuel-air ratio more noticeably at idle.
- Less commonFuel line or filter partially cloggedReduced fuel flow shows up first at idle before affecting full throttle.
What to do
- Warm the saw up for a couple minutes before making any idle adjustments.
- Locate the idle adjustment screw (usually marked 'T' or 'LA') on the carburetor and turn it slightly clockwise in small increments to raise idle speed.
- Clean or replace the air filter if it's dirty.
- Check the fuel filter inside the tank for buildup and clean or replace it.
- If idle remains rough after adjustment, inspect the intake boot and carburetor gasket for cracks or looseness.
- Avoid turning the H or L mixture screws unless you have a tachometer, since incorrect adjustment can damage the engine.
- If idle problems persist, have a small-engine shop clean the carburetor and check for air leaks.
Tools and parts
- Small flathead screwdriver
- Air filter
Carburetor rebuild kitSearch: “chainsaw carburetor rebuild kit”
Intake gasketSearch: “chainsaw carburetor intake gasket”
When to call a pro
If the idle screw alone doesn't fix stalling, take the saw to a small-engine shop for a full carburetor tune-up.
Safety
Use caution
Keep hands and clothing clear of the chain whenever the engine is running, even at idle.