Just a pet project I'm working on. Trying to track down when the reinforcing gussets existed (behind the left rear cylinder stud). This chart shows what I've been able to determine so far.
XS1/XS1B engine case revisions by serial number
1970 XS1 S650-
000101 - Rev-0 case, no reinforcing gussets behind left rear cylinder stud.
001235 - Rev-1 case, Gussets?, Transmission mainshaft needle bearing OD change.
003430 - Rev-2 case, Gussets exist, longer left & right case cover screws.
1971 XS1B/F S650-
022833 - Rev-3 case, Gussets behind left rear cylinder stud discontinued, Front mount nose shortened.
What I need is to find out if Rev-1 cases (S/N 001235 to 003429) started showing those gussets. Yes, that's a narrow range of serial numbers, this could be difficult. We know for sure that the rev-2 cases have these gussets, and that they were removed on the rev-3 cases.
Here's a top view of the first Rev-0 case, showing no gussets.
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