Idles at full throttle

Please check the following:
- Throttle control cable adjustment.
- Foreign matter in throttle plate.
- Fuel line clogged.
- Water contamination in fuel.
- Vacuum leaks in the intake manifold or at the carburetor.
- Carburetor base gasket or seal.
- Air/ fuel mixture adjustment.
- PCV valve.
- Valve clearance.

Adjusting carbs on chainsaws is not to be taken on lightly, there will normally be three screws, an L screw, an H screw, and an idle scre, the L screw will increase the fuel mixture from idle to half throttle ( they are fuel screws not air screws ) the H screw will adjust from half throttle to maximum revs, start with a base setting of between one turn and one and a half turns out, start the saw and warm through, allow it to idle, if need be increase the idle screw to get an idle, turn the L screw in slowley, the revs will increase as the mixture leans off, it will reach a point where it starts to die, now back it off a quarter of a turn, blip the throttle, the saw should pick up clean, if it has a flat spot increase the L screw slightley, now set the idle so it idles without the chain moving on the bar, now screw the H screw in to get full revs, be aware this should be set with an engine rev counter, do not exceed the manufacturersmax revs, hobby saws normally run at about 12500 rpm with an idle speed of 3000 rpm.

Sounds like the main jet in the carb is clogged, pull it and take a look, clean it our with fine copper wire and some gas.

sounds like throttle cable.replace both, and you can adjust idle with adjustment knob look under carbs for round knob about an inch big.

There are adjustments on carbs for low speed air intake (air mixture screw)find out factory settings and reset that mixture.Sounds to me like those adjustments are out of sink.If so the bike will run very bad from idle to about 1/4 throttle then run great from there up to full throttle.this definitly sounds like carb problem.

hello lloyd...... definitely pull the carbs and rebuild them. Since you did everything else right, this alone should fix the problem. Joe
Thanks for choosing Fixya!

You need to fix the fueling first - without fuel it won't run!
Your other problem sounds like an air leak - either the manifold or the carb. Check by spraying WD-40 or CRC at the manifold and carb join while the bike is running - if the revs change (either up or down) you have a leak.

Remove the throttle stop adjuster and the air screw adjuster and spray carb cleaner in the holes.
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two adjusters down. Only screw these in until they LIGHTLY seat. Now turn each adjuster one and one half turns outward. Turn the pilot screw 1/4 turn counter clockwise. Check the float level. Before putting the slide back in the throat of the carb, move the clip on the jet needle one notch lower.Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. Adjust the idle speed with the Throttle stop screw. This process should get you back on the road. A “very helpful” rating for this answer? Thanks!