Wheel bearing replacement
 

I have just replaced all my wheel bearings and seals. Approx. 4000km. 2 of them needed replacement due to water ingress, the others felt OK but I replaced them anyway. I used SFK bearings and seals sourced at trade prices direct from SFK New Zealand head office. This worked out to be about twice the price of the "All Balls" kits which I could have bought on line. I hope it was worth the extra dollars. I must admit I was a bit suprised. The 2 front bearings were $NZ 35 each due to being "narrow", according to SKF.

As for the infamous spacer between the 2 sprocket side bearings.... I found mine to have the same dimension step on both sides, so it could fit either way. It is simply a 2mm spacer that keeps the 2 dissimilar sized inner races apart i.e squeezed together when the axle is tightened. Wear is evident on both sides of this spacer - seems like a bit of poor engineering design, and then to make the thing out of aluminium? ?

Iv done 100 hours and just replaced both my wheel bearings. I used the all balls kits, but pulled the seal back and filled with more grease.
As for the spacer, I found that mine was definately directional, should be slightly concave. I think the spacer is there to distribute the force of tightening the swingarm bolt away from the centre of the bearing the axle runs in. The spacer runs in the outer bearing, gets loaded up from the axle and the spacer is pushed onto the outside on the second bearing. If it wasnt there, then tightening the axle would crush the bearings.

The front wheel bearing kit is the same as the kit for an LT50 :D

Um.. I think you will find it was concave because it has been distorted that way due to RShit design. On one side you have the inner race of the 6004, on the other you have the inner race of the 6005. These are being squeezed by the axle, via the large stepped (outside) spacer thingy - that has a land machined into it which is squeezing the (outside) inner of the 6005. Its smaller central land is recessed and doesn't bottom out on anything.
This means there is a shear type force on the 2mm aluminium spacer washer, because of the 2 different inner race diameters, and that's why it was concave. Mine wasn't but there was some wear marks on each side wear the inner races were. It's hard to put in words but I know what I mean!

The underlying principle is : the inner races of all the bearings must be squeezed tightly together by the axle. The outer races "float" in the hub