Whats the deal 3rd set of front wheel bearings
2 Q's...
1 - Do you pressure wash your bike, or ride up to the front axle in mud or water allot?
2 - What characteristics do the bearings display when you've decided they are "bad"?
OK, actually 3 Q's...
3 - Have you ever repacked the bearings? (yes, sealed bearings ARE repackable)
I've found that more times than not even "new" bearings have a surprisingly small amount of grease in them. I reccomend using a dentists pick or hobby screwdriver to carefully remove the seal on the outboard side of the bearing (when installed in the wheel) or both sides (if the bearings are out) & then clean with a contact cleaner, such as brake parts cleaner, & repack with as much high-temp, high-viscosity quality grease as you can jamb in it. Re-install the seals (easy to do without tools) & you should be good to go. For how long? That depends on how much you ride & wash your bike.
I went through the same thing with my 426. The front wheel would not rotate properly so I replaced the wheel bearings, seemed better until the next ride and the bearings appeared bad again. I pulled the axle and could not find anything wrong with it, I replaced it anyway and the problem was solved.
I am wondering about the center spacer between your bearings. If this is slightly short it could put a major side load on your bearings.
2 Q's...1 - Do you pressure wash your bike, or ride up to the front axle in mud or water allot?
2 - What characteristics do the bearings display when you've decided they are "bad"?
OK, actually 3 Q's...
3 - Have you ever repacked the bearings? (yes, sealed bearings ARE repackable)
I've found that more times than not even "new" bearings have a surprisingly small amount of grease in them. I reccomend using a dentists pick or hobby screwdriver to carefully remove the seal on the outboard side of the bearing (when installed in the wheel) or both sides (if the bearings are out) & then clean with a contact cleaner, such as brake parts cleaner, & repack with as much high-temp, high-viscosity quality grease as you can jamb in it. Re-install the seals (easy to do without tools) & you should be good to go. For how long? That depends on how much you ride & wash your bike.
ok to your questions:
I always pack as much grease in every new bearing possible and then stuff it full even more..
not much mud an no water - MX only unless freshly watered track - no direct contact with pressure washer - DUH - I know
I can tell bearings are shot by side to side movement of the entire wheel - you can see free play at the axel - also see bearing grease on outer hub at seal - seems the excess grease I stuffed in there is blowing out - this is the 3rd freaken time -
Always have replaced with OEM yamaha bearings - now I am trying Pivot works ... 
You may already know but, your bearings are not special. You can also get them from any bearing supplier or anyone that sells metric farm equipment. The reason I say this is because OEM is usually about three times higher priced for no reason. If you look at your bearing you will find a name like "NTN" "NSK" or something else. Next, you will see your number like "6204" or "6203" . Lastly just make sure your bearings have seals on both side.
TW
David,
It's because you practice the Fine Art of GORRILLA MX........
Easy there Big Boy!
Bonzai
David,It's because you practice the Fine Art of GORRILLA MX........
Easy there Big Boy!
Bonzai
what the heck is "Gorrilla MX"
It might be the bike shoe. 450s are significantly lighter than 426s. How? Lighter swingarm, hubs, etc. Yamaha reduced weight everywhere and it can affect reliability. There weren't many complaints of 426 hubs exploding; not uncommon on 450s.
Front wheel bearings on Yamahas have been an issue for quite some time. The reason is because they're not sealed.
You don't need to put the OEM bearings back into the bike. I recommend you find an alternative that is sealed. This will help with the longevity emensly.
You can find sealed bearings from a bearing supply store or sometimes at your local auto parts store. All you need to do is take one of your existing bearings in and they should be able to find you a sealed alternative.
Another reason your bearings could be getting premature expiration is that the seals and spacers are worn out. If the spacers have pretty good size grooves in them then it's time to replace them. And if you replace the spacer then you should definately replace the seals too. Also, I've heard ZipTy's wheel spacers are better than stock for longevity, so you might want to try these too.
And last, a pressure washer is instant death to the stock front wheel bearings. It takes very little water to waste those bearings. The upper headset bearing suffers the same issues with the power washer.
Good advice the spacer does have the grooves worn on them - i will replace - more money
yeah my bearings on my 450 are toast-had the same problem with my 250 before this-the only thing i started doing was greasing the new bearings before install and changing the seals and wheel spacers when putting on new tires helped alot on the 250 but i havent really done anything on my 450 since i bought it-time to work on it once i can walk again.
Replace the wheel bearings and stop using the bike shoe. If it doesn't happen again, then you know it is the bike shoe that is causing it. I was reluctant in buying those "bike shoes" in the first place because I was worried about the hubs and the bearings.
ok to your questions:I always pack as much grease in every new bearing possible and then stuff it full even more..
not much mud an no water - MX only unless freshly watered track - no direct contact with pressure washer - DUH - I know
I can tell bearings are shot by side to side movement of the entire wheel - you can see free play at the axel - also see bearing grease on outer hub at seal - seems the excess grease I stuffed in there is blowing out - this is the 3rd freaken time -
Always have replaced with OEM yamaha bearings - now I am trying Pivot works ...
Sounds like you're on the right track. I was just trying to eliminate variables. Something I was not aware of though... YZ's don't have sealed bearings!?! (Hmm, I'm guessing my WR does'nt either then... to the garage!) Like others have said, I'd go with new sealed bearings & consider new spacers, both the outer ones & the one inside the hub. Let us know how it works out.
I have always used med - hig temp marine bearing grease and have never had an issue with any bearig. I repack twice per year and they look new every time the grease is in pristine condition.
I reckon a lot of these problems are related to using grease that lose its characteristics the first time it sees water.
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On my 426's (5 of them) I never had issues with front wheel bearings...On my 03 450 I am going on my 3rd set - Anyone else having issues?
I do use a ATK Bike shoes on a trailer to transport - I never had issues before - could this be the culprit?
thanks