So we just put a new rebuilt 800 motor in an 07 800. The old motor tossed the crank.... the rebuilt motor was for that year bike, identical, and built by a repubal builder.. .. we plumbed it in with all the old stuff... sensors, injectors and what not. Start it and it runs great but put a significant amount of black smoke out the exhaust.... we thought it was just clearing out assembly lube at first but it hasnt cleared up after an hour or so of run time... it has to be over fuelling ? Plugs are new, filter is new, could the o2 sensor be bad ? Would maybe getting the computer reflashed help ? All suggestions are welcome. Thanks