Locked up but still had oil???

Ok so I have a 04 YZ450f keep up on maintance, not too many hours on it, not sure the real count, but was trailriding with my friends, we were pretty much wide open, let off for a corner and she locked up on me..so I've torn it down and indeed the big rod bearing appears to be locked up, I can move it just not very good, def my problem area, so this is where I'm baffled, there was oil in bottom end, head, cam, valves are all fine with oil, and cylinder is good too. Wristpin is free as can be the only thing that appears to be damaged is the big rod end bearing. The rod doesn't seem to be discolored or anything like there was a excessive amount of heat, also it appears everything else (counter balancer ect) all turns freely like it should. So I guess my question is what can cause this failure. Guess I've never had one lock up that had oil in it. I just don't want to put it back together only to have it do it again, but I'm not real sure where to start trying to find out my problem. Any thoughts, or suggestions would be appreciated. Thanks.

Sometimes they just fail its rare but possible the bearing cage could fail or a roller could crack and take the bearing out . The oil path to the big end bearing is through the clutch cover if you flip it over there is a seal in there that fits over the end of the crank. This seal normally does not fail but if it gets damaged or hard with age you would lose pressure to the rod bearing also you can see a passage from the oil filter area to this seal if it got blocked somehow same problem.

Geoffit, Thanks alot, I will check that, I thought that the cage got oiled by the splash method, so thanks for letting me know about that, I will be looking into the passage and seal. Thanks again.

In very high hour units, more so on the '03's, the bearing cage can split as mentioned, which lets the rollers become misaligned and locks the bearing.

grey, not sure how many hours, no hour meter, however there will be one when I put it back together, I just wish that I knew for sure, don't want to put a crank in it just to have it happen again but all this makes sense and makes me more easier with putting it back together. Thanks again.

Deffinatly just check your oil passages, pump and pickup filter. Also check, all the other bearings in the engine will need cleaned or replaced. When you press your crank apart you should be able to tell if the cage broke or a roller cracked. When the cage broke in my turbo bike it got bits of the cage in almost all of the other bearings. I was able to clean them and free them up. I did replace the main bearings to be safe. Blow through the end of your crank when you get it back together, to make sure the oil passages are aligned.


I checked my crank passage, oil passage to crank all good and open, the seals that go to the crank were kinda hard, not real pliable, so I'll be replacing those, oil pump seems good, can turn by hand, but is no really loose, thinking i'll be replacing that just because I think that it should turn more freely with no effort (please correct me if wrong), other than that, yeah thanks so much for all the comments, if you can think of others, let me know. thanks.

I had a 03 450 bone stock engine , i did a full race prep on the bike after every ride , i was in a desert race first place a 1 min & 1/2 in the lead when the crank locked up on me - and like i said FULL RACE prep after every ride or race . The 03-05 yz450s had that problem & the salution was the HOT rod crank ( stock size crank ) go with a stock size Athena pistion ,KIBBLEWHITE stainless steel valves, do a little head work with the intake & exshust ports & mabe if youv got the exstra cash hot cams ( you dont realy need it for trail ) That will be a realy badass!! running 450 after the rebuild

Thanks Daniel, that is the way that I'm going to be heading I think will put the crank in, piston, and ride it like I stole it, head looks great prob will leave it for one more season. Thanks for the info. I know they had problems 03-05 but ya know how it goes, you never think its going to happen to you type of thing...:busted:

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