Fine Tuning Screw L Low Speed Fuel Adjustment Screw
The screw with the {L} marking is the Low Speed screw. Set the low speed fuel adjustment. Slowly turn in the screw until the engine surges or starves for fuel. Make a mental note of the position of the screwdriver slot. Now slowly turn the adjustment screw out and the engine should run better. Keep turning the screw until the engine starts to load up. Make a note of the position of the screwdriver slot and compare it to the position of the lean adjustment. Now slowly turn in the screw to a position where it idles the best. It should be about midway between the rich and lean settings. Slowly we lean the low speed adjuster by turning it in, till the idle climbs and it then starts to die. Then we go rich and hear the saw start to blubber and the RPM’s drop, almost to a point where it dies. The optimum setting is between these two extremes. If you think you’ve found just the right spot squeeze the throttle and the saw should rev up without any hesitation or stumbling.
Fine Tuning Screw H High Speed Fuel Adjustment Screw
Best method is to turn the {H} screw out 2 turns and fire up the engine. With the engine running full speed, adjust the {H} screw outwards until the engine exhaust burns slightly black and or blue smoke. Then turn the same screw inwards until the engine just starts to run too lean. This may be indicated by a drastically or slightly increased speed just before the engine appears to die slightly or totally. The center point between the 2 extremes is often times but not always, the best setting. On a 2 cycle engine. I adjust the high speed rich, causing it to slow down and bubble. Then we adjust it lean causing it to sound smoother and then it starts to starved Screw