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help with a yz250f, please?

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I know this is the kx250f forum, but I ride a kxf and know there are some knowledgable guys in here.

I have 2 sick Yz250f's that I brought to fix up.

One is an 07 that skips in 5th (but doesn't rattle), its been stripped to order parts.

The other is the problem, I brought a 09 as a running bike with a loud rattle sounding like it was from the front/top. It's now been rebuilt serveral times and I'm at an end of ideas.

First I replaced the balance shaft bearings, made no differance,

then I swapped the 07 piston, barrel, complete head...no differance

swapped 07 cam chain...still rattles

Just done the main bearings...still bloody rattles.

What can I try next???

The rattle is through the whole rev range, and engaging the clutch or gears makes no differance.

Please help

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At least older Yamahas had a bronze bushing in the clutch basket. It required more play than a "nomal" bearing and the end result was usually noise. It was also amplified by the very thin magnesium clutch cover.

I remember the noise almost completely disappearing when I put a finger against the clutch cover.

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On the 07 trany, most of the time it takes 3 gears, shift fork and c-clip to fix the skipping or jumping in and out of gear. The pinion (or slider gear) and the wheel gears on each side of the pinion, plus the shift fork for that pinion gear needs to be inspected and I bet replaced. Any shinny or rounded off edges of the dogs on the pinion gear and look on the inside of the wheel gears where the pinion mates up with the wheel gear (the little windows or hole in the wheel gear. That is your problem.

The rattle snake 09, have you looked to see how much slop the clutch basket has? the center bearing could be worn out or the clutch basket center could be very loose and have side to side play in it. This will send sounds all over the motor and travel threw the crank. I would also look at the cam chain tensioner.

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On the 07 trany, most of the time it takes 3 gears, shift fork and c-clip to fix the skipping or jumping in and out of gear. The pinion (or slider gear) and the wheel gears on each side of the pinion, plus the shift fork for that pinion gear needs to be inspected and I bet replaced. Any shinny or rounded off edges of the dogs on the pinion gear and look on the inside of the wheel gears where the pinion mates up with the wheel gear (the little windows or hole in the wheel gear. That is your problem.

The rattle snake 09, have you looked to see how much slop the clutch basket has? the center bearing could be worn out or the clutch basket center could be very loose and have side to side play in it. This will send sounds all over the motor and travel threw the crank. I would also look at the cam chain tensioner.

At least older Yamahas had a bronze bushing in the clutch basket. It required more play than a "nomal" bearing and the end result was usually noise. It was also amplified by the very thin magnesium clutch cover.

I remember the noise almost completely disappearing when I put a finger against the clutch cover.

Thanks for the input guys.

I have just swapped the balance shaft, and cam chain tensioner and still have the noise.

The 09 runs a coller not a bearing on the clutch basket.

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Tried a few more things, and thinking it probably is the clutch basket/coller. what to change/buy though a basket, collar or both? And what would cause it??

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Maybe the whole main transmission axle needs to be changed out. I´m not quite sure how the Yamaha is built. I would suggest taking it apart and look for wear and measure the parts.

Begin with taking the clutch basket out and compare it to specs in the manual.

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