How do i adjust the carburetor high and low mix on a weedeaterblower fb25..

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).

I don't think so. Adjusting the high and low on carburetor is a thing in the past.

Typical for any carburetor is 1 1/4 to 1 1/2 turns (out). These are just rough settings to get the saw running. Remove chain, turn idle throttle speed screw in to increase idle rpms so its less likely to stall. Follow mfg instructions for starting.

Once running, adjust low speed mix and allow a couple minutes to warm. Then re-adjust low speed and lower idle rpms by turning out idle throttle speed screw. Then with throttle wide open adjust high speed mix. If saw hesitates from idle to full throttle, open low speed mix 1/8 turn and readjust high speed mix.

If saw doesn't fire in 3 or 4 pulls remove plug. If plug is dry no fuel, if wet either no spark or idle mix to rich (or fuel metering may be fouled).

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.

You have a c@carburetor issue.. the needles need adjusting

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.

Regular unleaded with whatever oil mix the fuel cap has on it.

Try to avoid gasoline with high ethanol content. You can look online and find alcohol-free gas in your area. You wont regret it!

Sounds like you will need to clean your carburetor.
Sometimes you can get by with priming it a few times, and letting it
run a few times like that and it will flush the gunk out of the jets,
but most of the time you will need to rebuild the carburetor.
If the mower is over a couple years old, then I also recommend that you
buy and install a new carburetor repair kit, because the diaphragm will
get hard and that will cause it to be hard to crank.
When you clean your carburetor and remove the jet screws, count the
number of turns it takes to seat the jets from their original position.
That way when you go to put the jets back in, you know how many turns
they were in/out.
Please do not forget to rate me, Thanks
Good Luck, I hope this helped

May need carburetor adjusting or you could have some bad fuel mixture. I would try mixing up some fresh mixture, not from your can in the garage, and see if that helps.
Good Day.

Find the 2 screws. There will be a (h) high and (L) low. These are for hig rpms and low rpms. First tighten the screws. Then unscrew them about 1-1/4 turns. Then start the saw and let it warm up. Start with the high rpms first pull the trigger all the way then adjust the screw in 1/8 turns either way until it is running good at high rpms. Then work on the L rpms. Get the saw to idle then pull the trigger, there should not be any hesitation when going from L to H rpms. Just adjust the low same as the High. They have to work together so if the high is good and the low is not just right turn the h a small amount. If you have any more questions let me know