Guys, When I crank my bike it backfires, after it gets hot it cranks great. I had the bike put on a dyno and tuned when I built the engine. I DID change the exhaust, a RB Racing 2 into 1 and I put a Heavy Breather on during my latest rebuild. I had a Samson Caliber 2 into 1 exhaust and a regular SE breather before (when dyno tuned). It also has some "Black" smoke that comes out just after cranking (the first time-cold). I would normally think that means its rich, but I would think if anything it would be running lean. Whats up??? O'yea its an 03 model bike with JIMS cylinders 10.5 CR, cams, head work, bla, bla, bla. Thanks in advance for any help/comments.
PS: I told the dyno guy that I was going to change the exhaust/filter later and he told me it would be ok to ride back (80 miles) to have it re-tuned that it wouldn't "hurt" the engine. Famous LAST words!!!!!

 

Take it a short ride 5 miles or so. Pull the plugs and see how thier burning. That is what I'd do first. Hope this helps