Dirt Bike Rod bearing seizure (pics)

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My 2001 Yamaha WR250F's rod bearing seized on me. I barely put 4 hours of use on it before it seized. The oil level was halfway between the hash marks. Anyway, I was hoping someone could identify what caused it to seize. I had someone press it apart. The needle bearing shattered into pieces.

photo2.jpg


photo1.jpg
 
Those scratch marks almost looks like someone pounded the wrist pin on there without any lube. Unless that was you that did that removing it.
 
you are funny

the wr250f does not have a needle bearing around the wrist pin.

and a 2001 that is 11+ years old with only 4 hrs. right, was it in a museum?
 
Originally Posted By: motor_oil_madman
improper assembly most likely.


Thats what I am thinking, probably had a broken roller from the start.
 
Sorry I wasn't clear: I bought it used and I put 4 hours of light use on it before it seized on me.

I don't know what oil was in it, I was going to change it after that ride.

I think the scratches are from removal, but am not sure.

There is a needle bearing for the crank pin, which is pictured (not the wrist pin.. the wrist pin was fine, and like someone mentioned, has no needle bearing)
 
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A picture of some of the other parts and the shattered needle bearing:
DSCN5554.jpg
 
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yes that can happen on the crank pin, not on the rod.

how plugged was the oil pump screen?

replace it with another oem crank.

doesnt take much oil to keep that bearing alive. so you have/had
an issue somewhere else.

ah now my memory comes back, dang been a long time since i've seen this. this must be a last run of 01 bikes. because this issue showed up on the early 02s.

the oil hole in the crank pin wasnt lined up and so it starved the crank pin. known issue on early 02s.

steve
 
Oil pump screen was not clogged at all. In fact it was almost perfectly clean. Oil filter had a good amount of metal shavings in it, but it wasn't clogged.

Top end was in good shape, but I replaced the piston and rings anyway.

I've replaced it with a brand new OEM crank (had a superseded part no) and also gave it a new OEM oil pump (which also had a superseded part number). I've also replaced the main bearings, countershaft bearings, and all transmission bearings.

Now I'm worried this will happen again
frown.gif
 
1st off let me say that it was a very limited number of motors that had that issue.

2nd, your bike is 11 years old. yamaha isnt even required to make parts for it.

that motor is designed just like an F1 motor. how many of those are around after 11+ years? or even 2.
 
That was a known issue with your bike. Put the new parts in and enjoy it. Make sure your valves are in good shape too. Dropping a valve will ruin your day.
 
Cool, and the new crank has the hole lined up properly, I imagine?

Just wanted to make sure I (or the previous owner) wasn't doing anything wrong.

Thanks everyone
 
Could be just from normal fatigue, Like what has been said these aren't lawnmower engines.
 
Any way to tell if it was an original or overhauled OEM crank that failed, or was it aftermarket?
Do you MX the bike or just trail / play?
Get an hour meter to keep track of your maint, and keep it off the rev limiter.
It could have been worse
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Put a hot rods stroker crank in. You won't be dissapointed. Yea. Definetly check all of your head out. Pro x makes pretty good valves. While your in there ya might as well overbore and put a new piston in. If you put in a wiesco (aka seizeco) make shure you let it warm up COMPLETLY before takeoff. If I where you I would run amsoil 10w40. Or If your not into synthetics id use valvoline..
 
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