Adjust speed - Audio Technica AT-PL50 Turntable

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.

there is a spring that is hook to the throttle through a lever if you bend the lever you can adjust speed

Hi Sean
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.
Bud

Hi Mark
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

Hi Paul
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

Hi montex124, I will try to help. In the past few years carb makers have been making changes. Some carbs have no adjustment at all, the ports are all fixed inside the carb. Other carbs have only the idle speed mixture screw that can be adjusted, like yours seems to have. Is this screw you mention at the top and completely outside of the carb to adjust the throttle? If it is it's probably the idle speed screw which can be adjusted to any idle speed you want and has nothing to do with the air fuel mixture but If it is right next to the idle mixture screw, it might be the high speed mixture screw but is capped so it can't be adjusted. The low and high speed mixture screws should be marked next to each screw H and L.
The 1 1/2 turns suggested is sometimes just right but other times has to be adjusted, so you can try adjusting it to get your idle but maybe adjust the idle speed screw first to get a higher RPM so it doesn't stall on you. Like I said earlier it just adjusts the throttle, and is like when you are using it, and giving it gas as they say. I hope this helps just a bit. Regards and good luck. Get back to me if you need more help or just let me know how you did. Denis.

bace line carb settings hope this helps
The adjustment on the bottom of the float bowl is the main jet. Adjust this one for high speed. The one on the side is your low speed adjustment. The one on top is your idle speed adjustment. Adjust your main jet at full throttle adjust it by ear till the motor smooths out. The low speed adjust it just off of idle. I always adjust by the sound to were the motor sounds the best. Your lucky newer engines don't have these adjustments.

Most likely this is caused by one or both of the following. The low speed jet needs adjusting or the idle speed is adjusted too low. Most saws the user can adjust the idle speed as the adjustment screw is not protected. Adjust the idle speed so that the chain just stops turning. It may be necessary to adjust the speed up till it will stay running for you and then start turning it down till the chain stops. If the low speed jet needs adjusting it may be a better idea to run it by a Stihl service center and have them tune it up for you.