At the risk of over-generalizing, most recreational dirt bike wheel bearings failures stem from water contamination, so easy on the power washer. Kawi OEM bearings that are only sealed on one side just don't last if you ride in wet conditions. Also, if your bearings are good, but your seals are crap (I'm talking about the outer rubber ones, not the seals built into the bearings) then the new bearings are not going to last long.
I was having problems with bearing failures until I went with a better quality double-sealed bearing. I'd seen the CBR website and was intrigued by the idea of a set of bearings that were pre-packed with good quality waterproof grease and came with a lifetime warranty. At $38 a set, they seemed pricey until a few other facts came to light:
1. The prices on the website have been lowered, the set was only $33 (
http://gate.tfb.com/~cbr/ ).
2. They came with new seals too ( believe the KDX uses the same one as yours).
3. My dealer was charging me $13 per bearing and $8 per seal. Total: $42
The guys out there are very friendly and answered all my questions.The bearings arrived in three days and were well packaged and individually sealed. The bearings were good quality NTN bearing. The new outer seals were a spring seal type and a much better design than the OEM KDX ones. The instructions were clear. All in all , I'm very pleased with my experience with CBR. Service was good. Quality seems high, (time will tell, eh?) and they are willing to back up their product with "lifetime" (to original purchaser) warranty.