YZ450 water pump free-play.

I am helping a fellow TT'er change the water pump seal on his '03 yz 450. The bike is now torn down. The pump impeller appears to have too much free-play. With the pump shaft inserted into the drive-gear, the shaft rotates about 15-20 degrees. When we did my kx500 recently, the pump impeller, which has a built-in gear on the end, was only able to be rotated a couple of degrees. Does anyone know if it is a normal condition for a yz to have that much play. We cannot detect any wear on any of the mating surfaces. I would hate to get his bike back together and have something cut loose. Any info would be appreciated. These blue bikes are still a little baffling to me.

Darn it Jeff... you beat me to my own question. Yes it is my YZ450F with the broken water pump. Like greenguy said, there is some play where the impeller shaft inserts into the gear. There is no signs of wear on the shaft or gear.

Any thoughts on how much play is normal or should there be none?

Thanks all..

There is normally a good 15~20 degrees of rotational play between the impeller shaft and the drive pocket in the balancer shaft.

Watch for an excess of play in the balancer shaft bearing itself, or in the impeller shaft bearing, or a groove worn in the shaft by the coolant seal that can be felt as a low spot with a fingernail.

You the man gray... I was waiting for your reply. I'm replacing the shaft, bearing, and seals tomorrow. The shaft has some pretty good grooves in it. But everything else looks great. I will accept the play as norm. Thanks for the reply.

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