My 1972 750 Cases Defect

Here's another defect in my 1972 750 engine. I think the quality control department was absent when my engine was assembled.

Aside from the white lithium grease on the flange, notice anything looking a bit off here??




Here's another view. The lighting isn't so good on this picture though.




Here I select a socket that is close to the tappet tunnel skirt outside diameter. It fits fairly nicely in the radius provided for the drive side tappet tunnel skirt. We can see it fits in there fairly well.





Now lets look at the timing side with the very same socket set in there.




Not quite right there, looks a bit snug.


Here's a picture I got off some ebay listing that shows what that area of the timing side case should look like.




Due to this overlooked radiusing of the timing side tappet tunnel location the cylinder barrel got pushed back so tight against the rear of the timing side case half that the cylinder barrel wouldn't fully settle down on the case flange. It sat .011" high at the timing side rear corner.

Yes, they are original matching numbers cases, not that it would make any difference in this issue.

I have already relieved this just enough to allow the cylinder barrel to freely settle on the cases.

I plan on further relief to allow some breathing room there when I get the cases back from Jim Comstock.

There was very little quality control at the time, I worked in the automotive industry 30 miles away 10 years later and it was not much better. Best not dwell too much, fix the functional issues and call the rest 'Character' or you will never finish the rebuild .

Like i tell all my clients :- They weren't made very well... If you can, look at the combustion chamber of a RH10 head, very often you will find them with the chambers in different positions. This lack of proper quality control affected the Americans as well. Prestolites QC was almost non existent. The last prestolite starter motor i overhauled had a commutator that was 12.5 thou eccentric (DTI had a travel of 25 thou) Its no wonder the Japanese took the motorbike world and made it theirs.