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69-76 to 77-78 Engine Case Interchangeability

richardchau

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Sacramento, California
Long story short, I'm looking to replace my top engine case. This might seem like a stupid question but I'm still relatively new to the chassis.

There's a guy local to me selling the top and bottom together for a decent price so I thought I'd pick it up however, it just so happens to be a 78 (my frame is a 72). Would I be able to swap the internals over to the 78 case?

Pictures below are of the 78 crankcases.
1715744939023.png
1715744950280.png
 
The problem you will run into is this newer case set is set up for an output shaft that sticks out further, you would run into chain alignment issues with the rear wheel sprocket. you would need a newer output shaft then try to make the alignment work with the rear sprocket...either different rear sprocket or adapter spacer, if you are new to this just look for correct cases. Watch on ebay for used case set no new than 75 for your application. You can not mix one case half with another, they are machined to match as a set.
 
The problem you will run into is this newer case set is set up for an output shaft that sticks out further, you would run into chain alignment issues with the rear wheel sprocket. you would need a newer output shaft then try to make the alignment work with the rear sprocket...either different rear sprocket or adapter spacer, if you are new to this just look for correct cases. Watch on ebay for used case set no new than 75 for your application. You can not mix one case half with another, they are machined to match as a set.
Got it, thank you
 
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