Just wondering if anyone can point me in the right direction. I bought a TZR (my third project) last year and let my son use the engine on his bike till we got his repaired. After about a week or so of using it the gearbox oil was like mayonase. His own engine was then repaired so I stripped down my engine completely cleaned all casings and gears and put it back together with new gaskets. The problem has gone away. I'm hoping its not a cracked casing? Anyone got any bright ideas.

Waterpump seal. Not uncommon. When it fails coolant gets into the gearbox.

The rebuild with im assuming new seals will have fixed it.