:bigsmiley25: When setting timing in correct positions am getting backfiring through intake and rocker box leaks, no excessive pressure in oil bag, also, when installing pistons, put pistion 'tangs' small lines on underside of piston towards primary belt side drive. Both manuals seem confusing on this point. Is this causing crankcase pressure to be wrong and causing oil leaks? Holes in gaskets and cyclinder line up. Doesn't seem to be a carb problem because simulated same problem with two different carbs. Static timing also set and no low rpm and backfires through intake but upper rpm revs okay. Could this be a valve problem? How do you set top dead center for setting the cam timing on 1975 Shovelhead because of two marks on the pinon gear of crankshaft?