Awhat is the adjustments on fast and idle scews

adjust the idle mixture screws first and then adjust the idle speed screw to compensate
adjusting the idle mixture screws will alter the idle speed but when properly adjusted then adjust the idle speed screw,

Check this link for fast idle adjustment.

Edelbrock Carburetors Troubleshooting Fast Idle Adjustment

Also check out the following link for details about the adjustment:

Pages 22 23 Choke Fast Idle Speed

screwdrivers
low speed adjust (scew in very slowly )untill the fastest idle is obtained.
High speed; Adjust to highest RPM while engine running wide open.
suggest taking line off. I,f while screwing either screw in, the RPM drops, open it (the screw)back up slightly.

proper adjust is tricky on these but to startadjust the 2 idle mixture screws at base all the way in then back out 3 1/2 turns. idle scew on linkage 1/4 after screw touches linkage

Start the bike and let it idle in neutral. Keep it idling for at least 8-10 minutes so the bike is good and warmed up. Once the bike is warmed up adjust the carburetor screw in or out little bits at a time until the bike idles at approx. 1800 RPM! Easy fix. Good luck!

If it's a constant speed engine with no adjustement for idle or a variable speed engine with no adjustement screw for idle , then it needs a carburator overhaull . If not adjust the idle scew , engine hot .

You need to adjust the throtte body near the carborator. Pretty simple process, just use a straight edge scew driver to adjust

Sounds like your idle fuel mixure is too lean, depending on how old you trimmer is, it should have 3 adjustment scews, one for the idle, one for the low idle mixure, and one for the high idle mixure. If all three are a flathead screw type you can make the adjustment yourself. look for the one labeled "low" and make your adjustment counterclock wise in 1/4 turn increments until it runs properly. you shouldn't have to adjust the high mixure screw. if you don't have the screw type adjustments, them you may need to buy a special tool (available at most lawn mower shops) to make the nessesary adjustment. make sure you leave the Idle Screw alone though( the one that move the cable) as adjusting this one will make adjusting the mixure harder to get right.

ok here goes. you are write to wind out the screws 1 1/4 turns +/-

you have 2 scews for the carb jets, the other is the idle speed adjuster. it has a conical shaft which simply open the throtle more as you screw it in. wind this in so that it will run a bit fast . if you can, start the saw. Without pulling the throttle, slowly turn the "low" jet in , or out untill the saw runs faster. if it starts running too fast, adjust the idle speed scew down a little. do this untill it is running best. adjust the idle speed down until the cahin just stops moving. the low speed is now set. now pull the trigger and run the saw full throttle. adjust the "high" jet in or out slightly until it is running fastest. Note..if you turn either screw in too far, the engine will stall.

I hope this helps,

Another thing that could cause problems is if there is an air gap between the carb and the cylinder. check that fixing screws are tight. check that the gasket is ok. some saws have a small rubber manifold between the carb and the cylinder. if this manifold is perferated or damaged,it will let air into the engine, and therefore will not run right.
good luck.

With the saw warmed up adjust the low for best idle.
Adjust the high for best speed then adjust a little richer from that point.
Caution......Running at best speed (power) settings which is "lean" will 90% of the time burn the piston......thats why you go a little richer on that setting.