I tried the complete range: -8 to + 12 and everything in between. The only thing that seemed to help much was extremely retarding the timing to –8, so it may be an extreme lean condition causing the bog.
I was thinking it had something to do with removing the magneto (~3lbs) which reduced the rotating mass and allows the motor to spin up more freely. So at the same throttle position the motor is actually turning more rpm due to the reduced rotating mass which means air/fuel flow into the motor would be affected.
Also, its my understanding that when these Keihin FCR’s are set up to make max HP, as mine are now, they don’t like to accept full throttle at the lower rpm’s (but it would before I installed the adjustable ignition timer). Anyway, I’m still going to try some needle changes.
Thanks for the reply,