Reinforcing gussets on early XS1/XS1B engine cases

TwoManyXS1Bs

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EarlyCaseGussets.jpg

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.
Early_XS1_Rev0_case.jpg
 
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Interesting... do those gussets give a stronger set of cases and, if so, why were they discontinued?

Haven't found any definitive published info on those gussets. My best guess is that they were added to reinforce the thin/dangling case overhang, in case of a thrown drivechain or debris. Discontinued, also unknown why. Maybe not necessary after all. Many of us think of them as attractive detail touchups on the early cases...
 
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...I have one bike in the Rev-1 range (0016xx).
It has the gussets...

Absolutely fantastic, txxs! Thanx.
Great pic. It even shows another obscure area of interest, the depression around the neutral switch, another pet project.

With this, unless there's any disputing evidence, I'll declare this investigation closed.

This is the revised table concerning the early XS1/XS1B engine cases, and will be added to the engine evolution post in the Bulletins thread.

Post #7
http://www.xs650.com/threads/yamaha-xs1-xs1b-xs2-tx650-tech-bulletins-service-data-brochures.31022/

XS1/XS1B engine case evolution

1970 XS1 S650-
000101 - Rev-0 case, no reinforcing gussets behind left rear cylinder stud.
001235 - Rev-1 case, Gussets added, Transmission mainshaft needle bearing OD change.
003430 - Rev-2 case, Gussets continued, 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.
 
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