Its running too lean..there is a plastic cover over the carb adjustment screws

some carbs have a small screw located in the throttle shaft at the lever
there may be a small plastic block that has to be removed first and then a small screw driver to adjust the screw
probably better to get a repair kit or new carby as that setting very seldom changes

Hi Mr. Martin:
Not quite sure what kind of adjustments you want to do.
All the chain saws that I've experience with have two slotted screws, one high speed, and one low speed. There may also be an idle stop adjustment screw.
Adjustments typically consist of:
1) with the saw running, adjust the low speed screw so that the engine is running smoothly.
2) with the engine running, increase throttle to maximum rpm and then adjust high speed by leaning (screw in) until maximum rpm starts to drop off, then back out 1/3 turn.
3) let the saw return to idle rpm. should be smooth, and chain not turning. Adjust as necessary.
Tool required is small screw driver. It can help if you put a small piece of plastic hose over the blade so that it will not slip off the head of the screws.
Cheerfuls

I'm sure you already tried adjusting the fuel/air mixture screw or screws. Look at the adjustment screws again, is there a plastic cap on the screw? The cap will have a slot for a screw driver. Look at the cap closely is there a tab that limits the adjustment of the screw? If there's a tab limiting how far you can turn the adjustment carefully pry or pull the plastic cap off. Be careful you don't want to bend the adjustment screw. Under the cap you should find a slot in the actual head of the adjustment screw. Turn the screw about a 1/2 turn counter clockwise then start the saw and let it warm up. Once the saw is warmed to running temp adjust the screws slowly a little at a time until your saw runs at normal idle speed by itself. I was amazed after I did this with my saw. Once my saw is warmed up I can set it down and it will idle until it runs out of gas. You may have to play with the adjustments to get it where you like. Basically the plastic caps on the air/fuel mixture screws are an EPA thing to reduce emissions, in other words keep the engine running as lean as possible. Running to lean causes stalling and since 2 cycle engines are lubricated by the oil in the gas to lean can wear the engine.

Poss diaphram problem, on the side of the carbs you will see a small cover secured by 3small screws, inside here there is a small diaphram used for adding fuel while you slow down from speed to save backfireing in the exhaust, when this fails exsess fuel is added to the engine while running, when you remove the cover dont loose the small oring

the mixture screw is underside of carb,if its between cylinder and front side of carb its fuel/air,to lean turn screw clockwise,if its between backside of carb and air box/filter,its air/fuel,turn screw counter clockwise to lean,adjust with 1/8 turn at a time.

The special toll your looking for is a thin bladed screwdriver. Some carbs have and idle and a "H" (high) adjustment only Others have third setting for "L" (low). The adjustment for idle (top of carb) is a personal judgment call but it should remain running at a low RPM. The adjustment for "H" Is done with full throttle and to the pint that it just does run at full speed without missing. DO NOT set it too lean (clock wise) or you will end up with a short lived blower. As far as setting the "L" speed (on models so equipped) you dial that one in by allowing the unit to idle then rapidly accelerate the engine to full speed. If it hesitates you turn it no more than 1/8 th turn each time and keep repeating the accelerate to full throttle rapidly routine until the hesitation stops. A few of these models have a plastic cover over the "H" adjustment screw. On some of them you can do about 1/4 turn with the cover installed but have to pry it off the jet screw head if further adjustment if required.

Thanks for choosing FixYa.

Kelly

No response to clarfication.

If you're talking about simply adjusting the idle mixture screw, you need to turn the screw inwards to lean it out. But, if you can get to the idle mixture screw, your carb has been modified as this screw has a "anti-tamper" plug covering the screw. The mixture screw is on the back side of the float bowl facing upwards.

More than likely, it sounds as if someone has rejetted the carb. That year model CV carb came with a a #42 slow jet in the carb. The modification to make them run better was to go to a #45 slow jet. This was in the original Keihen 40mm CV type carb. You can try to adjust the mixture screw and see if that allows you to pass. If it doesn't, repost and let us know. Maybe we can help you rejet your carb. Good Luck!

Could be running too lean, Should be runnning 50:1.

fist thing is run both the carb screws all the way in then back them off 1 1/4 turn this will be your starting point then start the blower to fine tune the carb if it starts then your carb was off giving it to much or to less fuel