Bottom End Assembly - Help Me Out Please!

So I'm helping out a little guy with his CR80. Somehow or another some straight gas ended up in his tank and he fried his rod bearings. I've been helping him with the rebuild but now we're running into a problem with the assembly and can't figure out what's happening...Hopefully the wealth of knowledge here on TT can help me out.

When I assemble the cases and torque the bolts to spec, the shift drum locks up. If I loosen the bolts, it will spin freely. I think when I torque the bolts, it's drawing the case surface into contact with the end of the shift drum, preventing it from rotating easily.

I have a parts breakdown and all pieces seem to be in their place. When I manually run through the gears (before case assembly) it shifts smoothly through every gear.

Is it common to require two base gaskets when reassembling? I'm sure another gasket will do the trick to offer more clearance for the drum, but maybe I'm looking past something.

If you can, please help me (and the little guy) out.



It sounds more like you have something like a chunk of gasket left on the crankcases, a dowel pin missing or in the wrong spot, crank/main bearing not completely seated, something like that that is not allowing the cases to close up in proper alignment. The shift cam is one of the few things in that assembly that runs directly in the cases, and so would be more sensitive to such misalignment than a shaft floating in a bearing. Remember that the shift cam is not contained in place by the cases, but by the little thrust plate on the right hand case behind the clutch. If it locks up without the thrust plate, it isn't an end play problem.

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