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Re: How do you adjust Idle speed
My 08 1098 had a very bad fuel leak that was visible. I was told that I overfilled the tank, but that was not it. What it turned out to be was a missing bolt out of the bottom of the injector body that let the fuel leak with ease. My local dealer could not believe what they had found, now it is leak free and I dont have the fear of bursting into flames riding down the road. I hope this helps.
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Most Chain Saw Engines Have Three Carburetor Adjusting Screws:
1. Idle Speed/Throttle Stop - This is the adjustment that controls how much the throttle valve (butterfly) stays open when the throttle trigger is released. If this adjustment is set too low, the engine will die when the throttle trigger is released. The throttle valve (butterfly) simply cuts off the supply of combustible air/fuel and the engine stops. If this adjustment is set too high, the high idle speed will cause the centrifugal clutch to engage and the chain will run. This is a dangerous condition and should never be allowed.
2. Low Speed Fuel Adjustment (marked L on carb, this is the low speed jet)- This is the adjustment that controls the proportion of fuel in the combustible air/fuel mixture at idle speed. An adjustment that is set too rich will cause the engine to load up and die at idle speed. A mixture that is too lean will starve the engine and cause it to race or surge. An extremely lean adjustment will cause the engine to die, too.
3. High Speed Fuel Adjustment (marked H on carb, this is the high speed jet) - This is the adjustment that controls the proportion of fuel in the combustible air/fuel mixture at cutting speed. It would not be accurate to say that this is the most important setting, because all of these adjustments need to be accurate for a saw to perform its best, but this is the adjustment that determines how the saw runs in the cut. An adjustment that is set too rich will not allow the saw to reach the RPM level necessary to build maximum power. Throttle response may also be sluggish and the engine would smoke and perform poorly. A mixture that is too lean will allow the engine to reach an RPM level where bearing failure and cylinder seizure are likely. It will also lack power in the cut and tend to run very hot.
The preceding information briefly explains rich and lean running conditions. It also identifies the three adjustment screws and their function. It should be noted that some chain saws lack the high speed adjustment needle. These saws have what is called a "fixed jet" which is set from the factory. "Fixed jet" carburetors are used to prohibit the saw operator from setting the adjustment too lean and damaging the saw. Unfortunately, they also often prohibit the saw from achieving maximum performance.
Generally you will find 3 small holes or slots on the pull cord side of the saw you will need a small enough slot screwdriver to fit through the holes. Depending on the age of the saw there will be a low speed adjusting screw a high speed adjusting screw and the idle set screw to establish which is the idle set screw remove the air filter cover from the top of the saw then the air filter you should be able to see the carburetor at this point, the screws should be on the left from the rear or handle end of the saw. The screw you are looking for should have a small spring on it and it should pass through an aluminum post and come against a metal lever of sorts on the top of the carb. When the screw is turned to the right the saw RPM should increase to the left should lower the RPM. When the RPM is lowered and the saw wants to stall the low speed screw will need to be adjusted. the low speed screw should have a blue plastic rotation stop on it and you may have to remove it to adjust the low speed adequately.
There is a new fuel made for 2 cycle engines that has a 50 to 1 rating and it cleans the carb and the internal saw parts. It's biodegradable and does not go stale in the saw. It's an amazing product. you should be able to get it at a chain saw dealer.Expensive but worth every penny. It comes in one ltr. or 1 gal. containers. Tune up in a can so to speak.
Hope this helps
Someplace near the carburetor should be an idle mix screw and an idle speed screw. There may also be a high-speed mix screw. Try turning the idle speed screw in 1/4-turn at a time until it idles. If you turn it too far, the clutch will always be engaged so the blade will never stop.
Once you get it to idle, adjust the idle mix screw in or out 1/4-turn at a time until it idles at the highest speed. Turn the mix screw in JUST until the idle speed starts to drop a little, then back it out 1/4 turn.
Now adjust the idle speed screw again until it idles smoothly at a low enough speed that the blade stops.
Most saws will have a high, low and idle screw adjustments.
First make sure we are dealing with a clean air filter, clean with air or tap air filter and brush to remove saw dust. Replace fuel if it is a season old or older. (Fuel filter replacement if it has seen years of use.)
2nd GENTLY turn the high screw clock wise until it bottoms out and then counter clock wise 1 and a quarter turns.
3rd do the same for the low idle.
It should run and idle at this point, let it warm up before making final adjustments. If it dies when giving it gas then more than likely it will need further adjustment on the low idle screw.
If it is really stubborn, often times the the ports are full of sludge from the bad fuel. I prefer to remove the bar and chain especially for the novice. Start the saw, secure with another set of hands if need be, turn the idle screw in to quicken the speed a little. Now you can work the low and high screws back and forth 1/4 turn while the saw is running, periodically giving it full throttle. That should be enough to dislodge buildup replace bar and chain and then your final adjustment.
If not you may have to look else where as in an air leak.
Generally this is a fuel / air ratio problem. Usually it can be solved by a carb adjustment.
On the carb there are usually two screws, one marked low or L , the other marked high or H.
Low is your adjustment for idle mixture, high is for mixture at full throttle. The saw should
Always be adjusted to run well during the cut. Make adjustments a little at a time, then try
The saw. Continue small adjustments untill the saw is performing well at full throttle while
Adjust the Low idle screw so that it doesn't die out. On most saws, to adjust the idle, look for an opening that has an L next to it (there is also one for high idle speed with an H next to it). Use a small screwdriver, and be careful--many of the idle adjustment screws are plastic so you don't want to strip it.
L is for idle speed mixture and H is for full throttle mixture. Adjust H, when engine is warmed up, with full throttle--adjust for high speed, but 4-stroking which should smooth out just as soon as you start cutting. Allow to idle and adjust L for smooth idle, but rich enough to allow the engine to 'follow the throttle'. Set idle speed screw to just allow the chain to stop moving.