Idels high speed or kills if I try to adjust lower
HUSQVARNA 455 with 18" bar and chain
recently changed air filter
need to choke even when motor is warm to start
Sometimes will run at lower idle speed but will always eventually kill out (approx 30 seconds or less)
Do not assume L or H adjustments are correct.
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Most 2-cycle chain saws have 3 carburetor adjustments; idle speed, low RPM fuel/air mix and high RPM fuel/air mix. The fuel/air mix needle valves will probably require a "special" driver tool to adjust them. Be careful with the adjustments, you can really mess things up by incorrectly adjusting them, then your saw goes from running poorly to not at all.
this is a sure sign of a fuel blockage some place !! id start with fuel filter and air filter and then look closely at fuel lines for signs of collapsing when running (CAREFULLY!!!!!) then move on to cleaning and resetting carb jets
remember choke richens fuel/air mix so if it needs choke to run then it's being restricted in fuel supply
Check the fuel filter, air cleaner, and muffler for plugging. Check the fuel lines for decay or other problems. Make sure that you have fresh fuel mix in the tank (50:1 ratio). Mix the fuel/oil in it's own container and shake the container thoroughly just before adding to the tank each time to prevent oil starvation. When you were cleaning the carburetor, did you check the condition of the lower diaphragm for flexibility with no holes or cracks? Turn both jet screws CW to stops (lightly), then back each out CCW 1-1/2 turns. Start the engine and allow to warm up, then pull the throttle full on. Adjust the H jet needle CW until the engine starts to speed up. Proper adjustment is when the engine 4-strokes unloaded, but immediately 2-strokes when cutting. Release the throttle and adjust L jet needle CW for better idle, but allows the engine to 'follow the throttle'. Hope this helps!
Remove the bar and chain--check the oil port in the side of the engine case where the bar fits up to. Start the engine--oil should ooze out of the port. If not, service the pump, lines and tank filter. If oil does ooze out, clean the chain groove, and the two oil passages that feed oil to the groove. If the outsides of the chain groove have flared out from chain wear, file these edges off (about 45 degrees) til they don't project beyond the bar vertical surface so that they don't catch on the kerf cut. Make sure the chain is being sharpened and adjusted properly. The 'choking down' may be from the engine overheating while trying make the cut. The engine should 4-stroke when running at speed, but immediately 2-stroke when cutting. Make sure the air cleaner and muffler are not plugged. Hope this helps!
That is where I would go. Maybe carb clean or kit if it is a sudden change. Carburetor Adjustment by Madsens.com http://www.madsens1.com/saw%20carb%20tune.htm CW is leaner; to lean will destroy the saw. If over tightened closed (CW) the adjustment screw faces are easily marred; marred adjustments are difficult to impossible to set properly. Clean the air filter; adjusting with a dirty filter can cause a run lean condition once cleaned and the saw run. There are 2 wav (sound - idle & full – may not be highlighted) files that I find most helpful, I think you will too.
If you have more questions or need additional help please reply below and I will get back to you. Thank you for using FixYa and Good Luck. HTH Lou
Your Idle and Hi speed jets are out of adjustment. If you look near the carborator you should see two, they usually brass screws. There should be markings by them one HI and the other Low for high speed and idel jet adjustment. You adjust the high speed jet for best running and power while sawing, then you adjust low speed for best idle. This needs to be done occasionally. Or take it in to a service shop. It is best if you learn to do it as from time to time it will be needed. When I was in my late teens I was a logger and these adjustments would need to be done 5 or 6 times a day.
If it is only running high at full choke - then it is not getting enough fuel.
You've cleaned out the whole thing - so it's not air that's the problem. It's running - so it's not a spark problem - it's a fuel problem.
If you have a fuel filter - change it out or clean it properly. If the fuel line is clear, then you need to adjust the running setting of the carb - there are usually 2 setting knobs -one for idle - one for running / mix.
You need it running richer till you get it going - then trim it back to stop it smoking and get a good rev.
ok, The choke is used to change the air/fuel mixture by "choking" off the air that goes to the carburator. The choke is only used to get the motor running in cold temperatures. Once the motor is started, the choke must be opened or the motor will flood and stall when you open the throttle.
I hope this solves your problem. Best wishes,