Adjustable timing advance

Started by rickj, August 17, 2003, 04:15:26 PM

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I installed a Yosh adj timing adv on my FZR400 and now I have a huge bog just after launching from a standing start. Are there major carb adjustments required after installing one of these?



What kind of timing adjustments did you make? Typically, little if any carb adjusting is required.


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,



Uh, you installed flat slides and reduced effective flywheel inertia in addition to installing an ignition advancer, and you wonder why it doesn't launch the same??


No no no. I never change more than one thing at a time. Bike ran fine with FCR's, then the only thing I did was to install the adjustable ign adv, which requires removing the magneto.

The million dollar question is when the mag is permanently removed to allow for the ign adv to be installed are there recommend carb adjustments that need to be made?  



by retarding the timing the motor will bog at lower rpm's but will usually rev up quicker up top,especially if you have done any piston work IE:high comp pistons. You cant get rid of the bog with the carbs, more compression would help...
Do you want to touch my Monkey?


Schedule some dyno time would be my suggestion, that way you can safely correct your problem.
Matt Drucker
MD Racing