Not neccessarlily the crank can be just enough out of phase enough to advance the timing put still be able to fire at the right moment, you said when your giving it gas its fine and runs great ? deff sounds like timing and I wouldnt count on the timing being set to 0 especially on a dune. Is there a degree section on your adjustable timing plate ? if there isnt your still running the stock one which is ok or its some "taiwan rip off plate" if the flywheel key looked great than I would also bet the cranks out of phase.