have a 99 sportster and recently had new pipes with a light baffle to help with back pressure, also had carb rejet to also help!! a couple days ago i noticed when i am at a light or just sitting still when revved it will puff some blackish slight white smoke. any ideas guys??? please help me with the problem. thanks guys

 

Is it actually smoking when the motor is revving up, or when the rpm's are coming down after you revved it up?

When revving up, the first suspect is rings.
When winding down, the first suspect is valve seals.

 

prob. just a little unburnt fuel from low rpm caused by rejetting. have a 09dyna that does the same thing.

 

I wouldn't worry about it much. I can get both of my Sporties to do that.