Fast Idle Speed

[EatenByLimestone]

I finally have my Grandfather's chainsaw running. I have a question about the carb. What does the fast idle speed screw do? How can I tell if it is adjusted correctly?

Matt

 

[EatenByLimestone]

I just looked in the manuel and the screw's official name is high speed mixture needle screw. The most guidance it gives is not to lean the engine out too much.

I wish I could go off car experience, but the only car I've had with a carb was my first, and it had a 2 barrel I couldn't adjust.

Matt

 

[elkimmeg]

with many carberators The high and low speed adjustment i I turn in the screws till fullly turned all the way in to the point of tight Not killed tight. I then back both out one full turn start the saw and listen to the motor for final adjustment the idle swrew is adjusted to the point where the chain starts to rotate and backed off 1/4 turn. I have had to adjust older saws to reflect the mixture till that fuel is gone. this can be common with older saws older saws used a 24 to 30 to 1 mixture new saws 40 to 50 to 1 mixture. You almost need two different mixtures one for the older saws and another for newer saws

 

[BrotherBart]

I can't help you with the fast idle speed but that remark about only one car with a carb made me feel really old. I think I will check Google for old folks homes.

 

[Roospike]

Here is a good start ..... If you need more help after reading this let me know. http://www.madsens1.com/sawtune.htm

 

[ourhouse]

with many carberators The high and low speed adjustment i I turn in the screws till fullly turned all the way in to the point of tight Not killed tight. I then back both out one full turn start the saw and listen to the motor for final adjustment the idle swrew is adjusted to the point where the chain starts to rotate and backed off 1/4 turn. I have had to adjust older saws to reflect the mixture till that fuel is gone. this can be common with older saws older saws used a 24 to 30 to 1 mixture new saws 40 to 50 to 1 mixture. You almost need two different mixtures one for the older saws and another for newer saws

What Elk said is a great start on any saw.

 

[slofr8]

I'll start with the screws out about 1 turn as mentioned before. I first adjust the low so it is very responsive to the throttle and does not idle to fast and make the chain turn. Then I turn (usually clockwise) the high so the saw sounds right to me. Not rough but not too lean as to spoil anything. Now adjust the idle screw as needed.
With my saws, Husky 266 and Johnsereds 630 (both from the early '80's when I used to log professionally) it ends up being about 1 1/4 out for the low and about 3/4 out for the high.
P.S. NEVER use the saw if you can't adjust so the chain stops when you release the throttle. It could need a carb. kit or have a broken clutch spring too.
Good luck. Be safe. Dan.

 

[ourhouse]

Check the clutch first. Also look at the carb boot to make sure its not cracked or torn. If it is the carb wont hold adjustment.