21-03-2018, 09:24 PM
It could be a tappet problem as R describes, but it could also be something hitting the crank as it turns. The last 2 or 3 inch and a half cranks I’ve installed, I’ve struggled to get clearance between the con rod and crankcase. The other thing I’ve noted is with new ( not original re ground) high lift cams, the cam lobe can hit the con rod every other rev. It sounds just like that.
Alan Fairless