2006 YZ250 Bad Vibration

So I just picked up a 2006 YZ250 rebuilt by JGR with an new case and refinished and re coated cylinder (no motor mods but 2013 cases were used) which currently has 3.6 hours on it with a few after market motor parts like vforce reed system, and a full pro circuit exhaust. When I first rode the bike the vibration didn't really seem that bad at all. I took it to the track saturday and  rode it and it seemed that the vibration got worse, almost so bad to the point where it gets hard to hold on when i give it gas since it vibrates soo much almost to the point of a shaking. I checked all the motor mounts and practically every bolt on the bike and made sure they were all tight, a few were barely loose whatsoever but it still vibrates horribly. Just for an example if its sitting there idling and I rev it it almost forces my hand of it vibrates so much, when it vibrates as well it sounds like ll kinds of metal is shaking against each other and as if the a few exhaust and motor mount bolts are really loose but they're fine. I plan on ordering some fasst flexx bars but I don't think that will fix the problem. The only things I could find by searching was some people saying that crank bearings can be going bad or a cheap quality crank was put in and/or its out of balance. As well as a flywheel weight being out of balance, installed incorrectly or going bad. I haven't checked the flywheel weight yet and I really don't wan to have the motor torn down again If i don't have to. Just spent over $2000 fixing a 250f that i traded this bike for. Quite violent vibrations? no loose bolts? Any suggestions? Also did an oil change after i got the bike before i rode, the oil still looked brand new but found this stuck to the oil screw magnet. No physical damage, scarring, its not broken. It's like a roller bearing almost but how it got there i don't know. Figured it accidentally ended up there after reinstallation since i couldn't find where it could come from without already have of locked down the motor or got chewed up at all. 


Sorry for DP but added along with the vibration part, some people say that running too low of an octane fuel can cause it especially if the timing is advanced? When I rode it at the track I only had access to 93 that day, usually i run 100 in my bikes (50/50 race gas and 90 non ethonal).

That looks like a needle bearing from inside the clutch boss.It will definitly cause a whole bunch of vibratoin. Does it feel or sound any diffrent when operating the clutch ??  Pull the clutch about halfway in while it's running it's possible you can feel it in the lever or the actuating arm. Easy fix if you catch it early.

Why not pull the flywheel cover off and have a look.

try give the fly wheel a wiggle.

That is a roller from a bearing somewhere in your engine. You need to find out where it came from. My advice is to stop riding now and take it apart so as not to risk additional damage.


First take off the right side cover and check the clutch bearing as mentioned above. Not sure where else roller bearings are used. Hopefully someone else can help.

i'm sure JGR would work with you if you had reciepts...If you just bought the bike, you now know why he sold it...People are liars and I doubt JGR ever worked on the bike.

So I thought I'd update what I've found, I stripped the clutch side down and the main clutch bearing was fine and the roller bearings in it were much bigger so that rules that out. Now what I also did find was that the 2 kick start gears (the one that the starter is on and the one that engages with the clutch basket) had some wiggle to them, is that normal? I also checked the flywheel and it was solid and wasn't moving whatsoever. I'm starting to think this vibration is normal however I could have sworn it was better the last time I rode it and I still don't know where that roller bearing came from since now I don't know of any other roller bearings in the motor, or any one that has that much of a smaller bearing.

My only other idea of how that piece ended up there was that upon reassembly it was accidentally attached to something. And souliog, I called the guy who built the motor (he works for JGR) and he told me everything about it. The motor only has 3.6 hours on it as of right now shown by the hour meter.

Is this the same bike as the trivia q in another thread? If not, pin should be #22. You'll know cuz it will fit right back in place. If not it kind of looks like the dowels to the waterpump cover, but I don't know how it would get into the engine unless it was stuck to there hand when reassembling.



When was the last time the top and bottom end were done?

What type of flywheel weight ?

Do you know if the flywheel weight was balanced properly ?

When was the last time you rode a 2t before you bought this bike? I ask because 2t always seem to have more vibration compared to 4t especially in the 2t powerband.

To moto349 yes, I guess my dad decided to post as well, but i ended up losing that little part so I'd have to get a new one, however we will check into that. To CRF, I grew up on 2 strokes and the only 4 stroke i ever owned was the last bike i had and I didn't keep it for long. The top and bottom was just redone and with new cases and cylinder all with 3.6 hours on it, I don't know what kind of flywheel is on it and I also don't know if it's balanced properly. However a flywheel wouldn't just all of the sudden come out of balance from the time i test rode it till after i was riding it for a while the next day, or at least I would think.

Could be wrong but it looks like a part of the bearing that holds the tranny. I'll find the part # hold on.

Edited by Peterrides

Well I thought I would copy and paste my reply to your dads similar thread if you haven't already read it

"Definitely looks like a needle roller from a bearing but could also be a drive pin.

It could be a dowel from the powervalve but I doubt it would have made it in the trans unless it was stuck to someone's hands during the rebuild.

You said you checked the clutch bearing so you could cross that off if your confident you had a good look at it.

First I would check the plastic water pump drive gear as it uses a drive pin of very similar diameter and length to rotate the shaft connected to the water pump impeller.

Second I would check the thrust bearing on the powervalve governor.

If by this stage you don't find anything you will probably need to split the cases as it may be one of those crappy plastic caged roller trans bearings or a thrust washer inside the transmission housing.

Good luck a report back with your findings."

If the bike is vibrating bad when revving in neutral its only going to be confined to the engine and not the trans. Its more than likely;

1. An unbalanced crank.

2. Unbalanced flywheel.

3. Piston is too small for the bore

4. Bad crank, big end, wrist pin or clutch bearing.

5. Damaged clutch assembly.

Or keep it as is and pretend its a shovelhead.

Check all your motor mount bolts, they could be lose. I had this problem before.

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