the bike seems to run well, but from the 2nd cylinder (from the left if you are sitting on the bike) it looks like there is oil (or black gas?) getting blown through the exhaust a little when it first is warming up. once the motor is hot it doesnt do this. a little bit leaks out of where the header meets the head of the second cylinder. the motor was just rebuilt a few hundred miles ago with a big bore (i think 700cc+). i pulled the carbs and replaced the jets, but not there's not much difference. could it be another issue in the carbs? or does that sound like something more serious? thanks, i'm new at this!