Take off the carb.

Clean it off as best as you can to get all of the glow fuel out that is possible.

Hook up a NEW clean piece of tubing to the input nipple.

Open the barrel up fully and blow through the other end of the hose.

You should be able to get a slow sustained HISS of air with just a little pressure build up.

If not adjust the needles until you do. Note which needle causes the greatest change.


Now close the barrel leaving about 3-4mm of the intake hole open.

Blow again. You should get a small HISS, but it will take some pressure to move the air.

Adjust the needles until you do....

Finally close the throttle all the way down, blow again. NO air should flow.

If you are unable to close the throttle fully, you may have to back out the LS needle ( depending upon design ).

With the throttle fully closed adjust the LS needle until there is no airflow if necessary.


The above should let you find out which screw controls which setting... and it will put the carb into the range where the engine SHOULD start, though the engine will be grossly out of tune.


I use this technique to check other people's problematic engines at the field....

It assures no blockage and at least minimum fuel flows, while identifying how the needles work.