06 yz450 oil pump drive/idler gear

The oil pump drive gear (not the gear on the pump itself) seem sloppy to me. Does anyone know how loose this should be on the shaft, or maybe even a spec on the clearance? It looks like (from the microfiche) that the shaft is replaceable, but I am guessing the case has to split (true?)

My engine makes a fair amount of noise (more so it seems than other yz's) but the noise has not gotten drastically worse so at this point my guess is that gear is worn.


The shaft bolts in from inside the cases, so they would need splitting to replace it. I doubt there's a significant amount of wear on it, though. If there is, you should be able to measure it by comparing the diameter of the shaft under the gear to the diameter just behind the retaining clip where the washer rides.

Don't know what the clearance is spec'd at for the gear, but it's a little bit looser than you might think. Most of the noise in a YZ450 comes from the primary drive gears rattling at idle, and from the transmission doing the same thing. The trans noise goes away when the clutch is pulled, and the gear noise usually disappears above idle. The idler gear really isn't big enough to add much noticeable noise to the mix.

Thanks, any guesstimates on how clearance there should be?

Not really. .002" maybe? Up to perhaps .004"

I'd hate to tell you that for sure then have you buy one with the same fit you have now.

No worries, at least I have a rough idea. I will take a really close look at the rest of them too. This thing was raced hard before I got it. I have pretty much replaced everything else in the last two years so it makes sense that the gears would be getting to the end of their life.

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