Bike jerky, more noticeable in 5th

[Schultzy101]

Just bought a used 2010 yz450f, so i dont have much history on the bike. It is jerking, more so in fifth gear, but in 3rd and fourth as well. Also its more noticeable at high rpm. Its not spuddering, like it would with fuel or spark problems. More like clutch or transmission. The engine revs up, and loses power to wheels. I do not hear any grinding or skipping when this happens, its more like if the clutch were engaging and disengaging momentarily. Thought i would jump on TT and fish for ideas!

Remember, i jus bought the bike yesterday(of course it ran fine on the short test drive) so i have no history on the bike. Any ideas or suggestions would be appreciated!

So far i have cleaned air filter, changed oil(amsoil 10w40 synthetic) and tried adjusting clutch cable. I also put in fresh premium fuel with a splash of sea foam.

[ViperGTS]

Just bought a used 2010 yz450f, so i dont have much history on the bike. It is jerking, more so in fifth gear, but in 3rd and fourth as well. Also its more noticeable at high rpm. Its not spuddering, like it would with fuel or spark problems. More like clutch or transmission. The engine revs up, and loses power to wheels. I do not hear any grinding or skipping when this happens, its more like if the clutch were engaging and disengaging momentarily. Thought i would jump on TT and fish for ideas!

Remember, i jus bought the bike yesterday(of course it ran fine on the short test drive) so i have no history on the bike. Any ideas or suggestions would be appreciated!

So far i have cleaned air filter, changed oil(amsoil 10w40 synthetic) and tried adjusting clutch cable. I also put in fresh premium fuel with a splash of sea foam.

 

 

The higher the gear, the more a slipping clutch will slip. Revving up but losing power to the wheel sounds like a clutch as well

[Schultzy101]

The higher the gear, the more a slipping clutch will slip. Revving up but losing power to the wheel sounds like a clutch as well

I agree. All i could come up with is it needs new clutch. Just ordered EBC fibers plates and springs. Ill let ya know if that fixes it! I just never had a clutch jerk like that so i thought id see if anyone else had any ideas! Thanks for the help man!

[joaquin1296]

Do you know how many blues? Sounds clutch to me. Aswell.

[Schultzy101]

How many blues??

New clutch plates and fibers go in today! Fingers crossed. I have this horrible feeling im going to have to split the crank case and change some gears or forks, but i sure hope not. Old clutch did look pretty worn. Plates were all that burnt purplish brown color. So either way, clutch rebuild was necessary. Ill keep ya posted. Thanks guys

Edited August 6, 2014 by Schultzy101

[grayracer513]

If the condition is that:

• The bike will take up to a certain amount of load without a problem, AND
• Applying more than that load causes a series of harsh jerking sensations as if the chain were jumping teeth on the sprocket and catching again,

... It's probably not the clutch, but more likely to be worn locking lugs on the gear sides.  The bouncing in and out of gear will have bent the forks as well.  Clutch slippage is hardly ever jerky, but rather more like the RPM rising without an increase in speed, same as riding on wet concrete, but without the tire slipping. 

 

It is somewhat unusual for this kind of thing to be happening in more than one gear at once, though, and if it's the same kind of shudder/jerk in all three top gears, with each higher gear being worse than the next lower, that is something that reasonably points to the clutch. 

[joaquin1296]

How many blues??

New clutch plates and fibers go in today! Fingers crossed. I have this horrible feeling im going to have to split the crank case and change some gears or forks, but i sure hope not. Old clutch did look pretty worn. Plates were all that burnt purplish brown color. So either way, clutch rebuild was necessary. Ill keep ya posted. Thanks guys

Sorry meant how many hours? I know you dont know much but for instance my original Yamaha clutch lasted around 50 hours. It was then I felt the bike really not well.

[Schultzy101]

Oh, the hour meter says 41hrs. Ya im not holding my breath. I think theres more to it than clutch. Will see for sure, as soon as i get time to put back together. Fibers are soakin in some amsoil as we speak. Would you guys recommend, if i do open up crank, to replace any bearings, gaskets, etc while its opened up? Im thinkin a guy might as well, since ill probably be payin the local mechanic anyway. Might as well not put old bearings back in? Anyone know a good site to order these parts from(in canada)? Again, thanks for the info guys

[Schultzy101]

Grayracer. Yes, it gets worse with more throttle for sure. And it does feel like teeth skipping... Except when it grabs, it isnt as harsh of a jerk as when, say, chain skips on sprocket. Thats kinda why im thinkin that the clutch is slipping, but also there are transmission problems as well.

Thanks for chimin in gray

[Schultzy101]

Changed clutch. No longer slips, but now i can tell its definately transmission related. Skips as though missin some teeth on fifth or something. I have a mechanic looking at it now. Thanks for the help everyone.

[grayracer513]

It's the locking lugs.  They're supposed to be very slightly undercut ("dovetailed") so they will hold together under a load.  As the wear, they loose that undercut and become rounded, then they start forcing themselves away from each other under power instead, deflecting the fork far enough to slip over the the lugs, rotate against each other until they line up again, and the fork slams them back together.  They pop out, again, engage again, so on.  Beats up both gears that lock together and bends the fork, which makes things even worse. 

[Schultzy101]

Ya grayracer i think your probably right. Having it looked at on tuesday. When i find out for sure what the problem is ill post it. In the meantime, i better start puttin in some OT, i have a feeling this isnt going to be a cheap fix haha

[Schultzy101]

Yup, grayracer, you nailed it. Thanks for all the input!