05 water pump leak

I had a mates 450 in a couple of months ago to fix the water pump which would dump about a 1/2 cup of coolant out of the weep hole at first start up but then once warm would not leak for the rest of the ride. I pulled it apart and the put 2 new seals in plus the shaft bearing, I did not replace the shaft as it did not seem to have any wear where the seals ran (fingernail test), so I linished it with some emery and put it back together with the new seals/bearing.

Now a couple of months later it seems to have the same issue, is it defiantly going to be the shaft or is there another issue I am not aware of?


The shaft could be the culprit. If there is any significant groove worn in by the seal, that will "trap" the lip of the new seal and lead to its failure.

The other thing is that the inboard end of the shaft is supported by the balancer shaft, and as such is supported by the balancer shaft bearing. If this has worn significantly, the clearance will cause an excessive amount of tilt along the impeller shaft, which the seal will be unable to handle.

If this bearing needs replacement in an '05 or earlier YZ4**F, the cases must be split.

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