a buddy of mine crashed his cb750 last year, dislodging a lost tappet adjuster locknut that had been hiding somewhere in the head. a short time later, one of the cam lobes caught it and punched it straight through the head to open air, causing a terrible oil leak. anyway, he swapped heads out from another engine, and after one ride, found that he had some problems. after teardown, he found that one side of the camchain sprocket mounting flange on the cam had broken clean off. i thought maybe he had not tightened the bolts down enough, and one had worked loose causing too much stress on the other, but he says that the other bolt was still bolted to the cam.
anyway, anyone care to guess what happened here? i have a hard time believing that a cam ran fine until being swapped into another engine,
then experienced failure due to metal fatigue or something similar. maybe the stress of the nut getting caught under the cam lobe caused a micro-fracture?
