Need to Adjust the carburetor -- the procedure to adjust the high speed and the low speed screws- don't have the red and white caps on the screws head like the manual states. Need the procedure from setting the screws all the in then how far out and in what order. Then how to set the throddle cable. thanks

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.

low and hi speed mixture screws
one adjusts for proper idle
one adjusts for proper high rpm operation
turn them in or out to get the best throttle response and proper wide open throttle rpm's

Hi F Del
Before you remove or try to adjust your low and high speed jets you should always count the number of turns it takes to lightly seat the idle mixture screw and high speed needle adjusting screws.
Be sure to write the number of turns down on a piece of paper so you will know how many turns from the seated position to open the jets when you go to reinstall them, or if you remove them for cleaning or replacement.
If you have aready tried to adjust them then the adjustments below should get it running for you for final adjustment when warm.
Normally you will adjust your idle jet to 1/2-3/4 turn open from the bottom seated position.
Then you will re-adjust the low speed of the engine when the engine is warm by turning the idle screw in or out till the engine runs smoothly at idle speed, around 1200 RPM.
The high speed jet is adjusted to 1 1/2- 1 3/4 open from the bottom seated position, after the engine is warm.
Then re-adjusted by turning the High Speed jet adjustment screw in or out till the motor runs smoothly at high speed.
Alway use the "lightly seated" method if you have not changed the screw settings.
Please take time to rate me
Bud

There are two needle screws that can be adjusted to make the engine run properly. Be certain that the carburetor is clean and the diaphragm is in good condition, and the fuel is new. The two needle screws mentioned above should initially be adjusted at one turn open from turned in all the way (lightly seated). Each of these needle screws performs different functions. One is for idle and throttle response (this screw is marked "L" and the other screw is marked "H". L and H are marked on the carburetor body and also on the plastic "shroud" near the adjustment screws. These screws are not interchangeable, being foolproof since the thread sizes are not the same. When properly adjusted the low speed screw (L) allows the engine to idle properly and throttle response will work properly. When the high speed screw is adjusted properly the engine will have correct power at full speed. Adjust the low speed screw so that the engine idles and when you squeeze throttle all the way to wide open the engine should not hesitate and should come up to full speed and when you drop the throttle it should idle nicely without stalling. Now adjust the high speed screw. Hold throttle wide open, holding it there while you adjust the high speed screw. If this scares you (be carefully so that the spinning chain does not cut you!) you may adjust the high speed screw at idle, turning it just slightly in or out. The high speed screw should be adjusted so that the engine does not run clean at wide open throttle but sputters slightly, slightly adjusted open from running clean to slightly sputtering. When under load (cutting a log) the engine should run clean. Good luck!

You need to disassemble the carburetor and check the diaphragm. You need to blow nozzle of carburetor. If the fuel was left in him, now it has remaining traces of oil. You can try to start with a small pump to inject fuel directly into the intake of the air into the carburetor. Of course, the spark has to be here to start. Older chainsaws had a switch and a capacitor, which is very difficult to adjust. Newer chainsaws have electronic ignition, so it is easier for test. Most of carburator has three buttons to adjust. L (low), H (high) for fuel injection at low and high speeds. There is also a minimum (the chain must be stationary if it is well tuned). The chainsaw is set at low rpm throttle with screws ( L ), and its vivacity is set at high speeds ( H screw ). In the beginning is good put both to set at 1.5 turns from full closure. And then, if the chainsaw starts, you can adjust a carburetor work. Careful with adjusting with H due to high speed. Good luck!

I don't know if you have a Zama or Walbro diaphragm carburetor on this unit, so I will give you tuning methods for both! Zama First....

http://www.zamacarb.com/tipspage.html and now Walbro.......

http://footflyer.com/fix/motor/carburetor/walbro.htm

Hi John, this is probably a carburetor adjust issue, but it could be something else like an air leak, plugged air or fuel filters or lines. A possibility could also be venting of the fuel tank. This is usually done by a one way valve in the gas cap. The carburetor itself could be causing this problem, and might need cleaning or a carb kit. Try adjusting the mixture screws that could be the problem. When adjusting needle screws turn 1/8 of a turn at a time. Start by adjusting the low (idle) speed mixture screw 1/8 turn out (counterclockwise) to add more fuel to the mixture (make sure you remember the start position). Start your brush cutter and see what happens. If you have to, do that procedure 4 or 5 times. If not any better, return the screw to it's starting position. You might try turning the screw in (clockwise) a few times and see what happens. For your info (the manufacturers suggest to adjust both the high and low mixture screws 1 turn out from a lightly seated position as a starting point to adjust carb. This is very often just right, but if adjustment is necessary it is usually not by much). If the low speed screw adjust has no results, try the same with the high speed screw. I hope this helps a little bit. Get back to me if you have any questions. All the best and good luck.

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

Sure. (This will void your warranty and bypass smog requirements!) There is a red and a white limiter cap on the carburetor adjustment screws. Red= High speed / White = Low speed. Remove limiter caps. Turn both jets a 1/2 turn counter clockwise, Start, then fine tune. Use the low speed and idle screws to smooth out low to idle speed and the hi speed jet to tune the full throttle.