Cylinder mounting studs
 

is there any need for the small turned diameter on the end of the m10 stud which holds the barrel to the bottom end? Its the threaded end which screws in the bottom of the engine not the part with the nuts on? Any help would be appreciated
Cheers Luke

It's probably for the type of tap used to thread the engine cases. They don't want the stud threads bottoming in the case's threaded bore.

Thanks gas gas man we presumed it was that. Just turned my self a nice new set of inconel ones..lol probably worth more than my bike lol