You RANG?? Howdy there friends and neighbors!!
Keep in mind that the pilot jet is
primarily responsible for idle to 1/4 throttle.
The needle is
primarily responsible for 1/4 to 3/4 throttle.
The main jet is
primarily responsible for 3/4 to full throttle.
Based upon that, look at the symptoms and decide what part of the throttle range the problems occur in.
If it starts and idles ok, and full off decel is ok, then the pilot should be right. If not then adjust screw &/or rejet.
If there are issues in the 1/4 to 3/4 throttle range then an adjustment of the needle is appropriate... like removing the white spacer for example.
Running at wide open full throttle should be crisp and powerful, without bogging down or shortness of breath. If there is a problem then the main jet needs to go up or down as appropriate.
You started out saying that everything was working OK, then without any changes on your part the engine starts to backfire a little. In that case, something did change ... otherwise the symptom would not show up.
You're only getting a little backfire at less than 1/2 throttle, and the idle is now
wavering. A wavering idle sounds like an air leak at the carb or a clogged passageway.
Adjusting pilot from 1 to 2 turns out, slows at each end of it (as it should with the correct pilot jet installed), so
1.5 turns out should be about ideal.
.
Holding the throttle open a little while shifting and during decel will keep the idle up a little higher which will help prevent backfires. Throttle off decel at higher speeds will enable the carb to keep a stronger air flow through the carb bore, creating enough vacuum to pull the fuel up from the bowl and making a decent fuel/air ratio, which prevents backfire. Throttle off decel at lower speeds creates less vacuum, pulls less fuel, making a leaner fuel/air mix, which will enable some backfire.
Idle speed adjustment alone only affects engine speed at idle ...
... in order to affect the typical backfire the adjustments
MUST be made to the pilot circuit. Adjust the screw and/or change the jet ...
as needed based upon the symptoms of the engine.PAUSE: GOT TO RUN TO THE PHARMACY ... BE BACK IN 30