Brewbrother wrote on 12/31/69 at 16:00:05:My limited understanding indicates that the spacer mod increases the amount of fuel in the carb circuit. I think the deciding factor is how many turns out you have to use for the air/fuel mixture. factoring in where it was preset at the factory. the origional post concerning this spacer mod was to open the carb remove the spacer and toss it in the trash can. Then adjust the air/fuel mixture. IMHO, whether you rejet or not depends on two main factors. The air fuel preset from the factory and where you are looking for your response point in the throttle. My main reason for the mod is engine life. I mainly ride in city traffic and could care less about performance. I have explored what the bike can do stock. I occasionally make a long ride, but almost always its a 14 mile round trip.
If you do the mods and everything is fine then you don't have to worry about the jets, but from what I've read about carb tuning is that you first have to find the proper main jet first before anything else can be adjusted correctly. I may be wrong, but just adjusting the mixture screw might help the backfiring, but the midrange and top end will still be very lean and that may not be very healthy for the engine too. Lean conditions can cause the engine to run hot and overheat and sometimes even melt the spark plug.
Pages: 
