03 yz450f water pump rotational free play

I'm just getting my motor back together, after the rod bearing seized.

My water pump impeller has a fair bit of rotational free play, I'd guess its about 80°. The water pump shaft is not very old, I replaced it when I did the water pump not many hours ago. The inside of the balancer shaft which drives the water pump shaft has rust in it. As far as I can tell, the free play is isolated to the water pump shaft inside the balancer shaft, and not the balancer shaft rotating as well.

The black marks on the water pump housing sealing surface are indicating the rotational free play.

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Should I be worried about this? Do I need to replace the balancer shaft?

That's a little loose, but surprisingly not much. What you are seeing is reasonably normal.

I guess I took that side cover back off to take a closer look for nothing. I'll put it back together, and keep on my re-assembly journey.

In an old thread I think I remember you mentioning 15-20° was 'normal', but I think that was on a 400 or 426.

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