Hey folks.. just doing a water pump seal and noticed behind the water pump a deeper hole with some sort of irregular shaped foil hole behind it. I'm chasing a problem with coolant in the oil, and what seems like an air leak. The foil is thin... and not circular, and appears to connect the water pump directly to the crank case. I'm assuming this is a problem! Can I just plug this hole? Its odd that it is not co-planar with the crankcase gasket. Circled it in the picture. 

There should be no hole there. JB Weld or new inner clutch case. The choice is yours.

 

Any idea why the out clutch housing and the pump itself have the hole/bore then? Not seeing the point unless it was just a feature used on a different platform. Also, this is a brand new clutch case! The hole is about 1.5 inches further into the crank case than where the clutch case meets the crank case. 

Edited December 13, 20205 yr by blast_off

Sorry, but I have no idea why the hole is there. I've had the clutch cover off on both the Rev3 and Evo series bikes and neither has a hole where yours does.