Engine dies upon acceleration after starting and idling

Implies carburetor low speed fuel circuit lean. Increase low speed fuel/air.

Initial setting is 1 1/2 turns. Increase idle speed enough to keep the engine runnning so a proper adjustment of the low speed air/fuel mix can be completed.

Basic rules; Always adjust low speed a/f first, then open throttle and adjust high speed a/f. Any low speed adjustment must be followed with a high speed adjust. Error on the rich side for high speed. Allow engine to reach operating temperature for final adjustment.

Other potentual issues, fuel quality, fouled carburetor, old impulse diaphragm (carb), carb to engine intake gasket leak, crankcase leak.

Removing tines makes it easier (safer).

https://data2.manualslib.com/pdf/8/741/74034-husqvarna/340.pdf?658888cc1e965ad6a8e290b6dfb24620&take=binary Review adjustment procedure starting at page 37.


It's a bit of an art and you have to be able to hear the slight changes in combustion and engine speeds. It took me years to become what I consider "proficient" and not struggle with adjustments of a 2 cycle. You must adjust the idle air/fuel mix first, then high speed. I read improper instructions regarding this all the time. The low speed circuit has to be set first because it changes the overall mix when high speed is open. Any changes in low speed air/fuel mix affect high speed (not the other way).


Start by remove chain. Begin with both H and L screws at 1 to 1 1/4 turns out. You want the idle speed high enough that it runs well enough to get through the idle mix adjustment without dying, but not so high that the carb high speed is opened. So if its dying while adjusting low speed, increase the idle speed. If you can't get idle adjusted without it dying, then likely you have other issues with the carburetor, spark, compression (crankcase seal) or even blocked spark arrestor screen.


Once you have low speed adjusted, you begin on high speed adjustments. See instructions. If the saw does not want to accelerate without stalling and you have opened the high speed screw, then likely the high speed circuit is fouled or there's a crankcase leak.

Turn both low and high adjustment screws carefully clockwise all the way in - do not overtighten.. Then back out each two full turns. Set the idle speed control for highest setting. Prime and start and let it run and warm up for about 15 seconds - then lower the rpms a tad and then adjust the low end screw for highest rpm. Then reset the idle to lower reasonable level. You may have to go back and forth with those two adjustments till it runs fine at low idle speed..

Then accelerate to highest speed and set the high adjustment for highest rpm. Then go from idle to high speed. If not smooth a small adjustment on the high speed screw is in order. Keep doing that until you get a nice smooth transition form low speed to high speed.

Your idling engine speed screwed to high "!" need adjustments it's holding the throttle open slightly allowing the engine to race at uncontrollable revolutions or to high an idling rpm The idling speed screw should. Located near or upon the throttle. Butterfly wind either in to slow the engine or out dependant upon the make and model of carberetor

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

If this vehicle is equipped with the cableless throttle, you need to try this first:
remove the air intake hose
clean the throttle door with an aerosol throttle cleaner
replace air intake hose
Upon starting, you may need to apply gas slightly while starting to clear the throttle cleaning chemicals from engine, continue to hold accelerator to 2000rpm for about 2-3 mins
release gas pedal slowly to allow ecm to relearn idle.
This procedure allows the ECM to relearn the vehicle true idle position.

Regarding the adjustment procedure you generally start your low and high mixture screws at one turn from seat, or slowly turn them in all the way until they bottom out and then back them out one full turn. You will adjust the high speed mixture screw at full throttle and get the median point between too rich (loads up) and too lean (dies out). You will want to do the same thing with the idle mixture screw, just adjust at idle rpm. You will also adjust the low idle mixture screw to give you a smooth transition from idle to throttle up. Once this is obtained, you adjust the third or idle speed screw low enough so the chain does not turn at idle rpm but high enough so the saw doesn't cut off. Hope this gets you going.

Is the idle speed set too low? If so, adjust it, using the idle speed adjusting screw, to the correct idle speed (900 RPM). If that's not the problem, then check for air leaks between the carburetors and the engine by spraying WD-40 around the intake manifolds with the engine running. If there is an intake leak, the engine RPM will change briefly when the WD-40 is sprayed near it.
Aside from that, there are two other things that can cause your engine to die when it should be idling: the idle speed mixture adjustment, or low cylinder compression. Of course, if it was idling fine before, and the idle mixture adjustment hasn't been changed, then do a compression check, first. To idle properly, each cylinder's compression needs to be at least 140 psi.

Sounds like your carburetor either needs cleaned or the needles need adjusted. Try turning them just a bit and continue trying to accelerate the engine. If your carb has adjustable needle screws, one will be the low speed adjustment and the other will be the high speed adjustment. You'll know when you have the right one when the motor starts to run just a bit better after adjusting the correct one.

turning Hi & Lo mixture screws in leans the mixture,out rich-ens it.turn the T screw in to increase idle speed the chain should slowly come to a stop at idle [chain brake off] adjust Low needle first until it accelerates smoothly then Hi needle for best 'revs'.then Lo again if necessary if you don't know where they were set before,start w/ screws 3/4 to 1 turn out from a lightly seated position