4th gear bad?

[Mazzeppi11x]

So i went out to the dunes yesterday and i started " losing" 4th gear. 1 2 3 are fine, but when i shift into 4th (it shifts into 4th smoothly btw), it feels like its slipping, almost like the teeth of 4th are worn down or missing a tooth. Anyone had this problem? Thanks

[husky300racer]

You have a bent shift fork and possibly a bad 4th gear! Time to split the cases:thumbsup:

[Mazzeppi11x]

so im assuming i have to replace the piston and everything too if i split it? i dont understand how it could be the shift fork. it goes into 4th fine, the problem only happens when i hit the gas and climb through the revvs

[husky300racer]

Yes it will shift into 4th just fine. but it's only partly engaging. As soon as there is a load on it, it jumps, causing a slipping of the clutch type feel. I would at least replace rings,piston and cam chain. Check all bearings and rod for play! and check valves for leakage with solvent once the head is off.

[Mazzeppi11x]

oh ok that makes sense. i just had a leakdown test done a week ago and it was still within 5% of new, and a valve adjustment was done. My mechanic and I are gonna tear into it tomorrow morning, i hope its jst the shift fork and not the gear. thanks

[1down4up]

Check the simple things first. Free play in the clutch cable(should have some), clutch condition and what kind of oil in the crankcase. some synthetics can cause a clutch slip.

[grayracer513]

The gear itself, and the one next to it, are bad. The shift fork is bent BY this condition, not the other way around. The locking dogs on the sides of the gears are supposed to have a slight undercut. When they wear, they round over, and start forcing themselves out of lock up against the shift fork, bending it in the process.

The top end has to come apart for this operation, but you need not replace any of it if it's in good condition. Rings are cheap, though.

[zZCRF450kmnZz]

yea check everything before u just jump into it. u dont wana rip it apart and have it be something else.

[Mazzeppi11x]

the clutch is golden, and its been progressively worse the last 2 weekends. it only happens in 4th, and its definitely the trans cuz i feel a slight clunk, not just a slip

[Mazzeppi11x]

ya, i definetly not gonna cut corners, i might as well replace the piston while im in there, and not have to worry about it. its an 03, its got low hours but probably needs it. i need this bike to last till yamaha comes out with EFI:thumbsup:

[Mazzeppi11x]

So my mechanic and I pulled the motor, and the shift forks look good, so im assuming its the gear itself. Hes taking it into his work (hes a mechanic at Alba Action Sports) and gonna split the cases. Well find out for sure tomorrow. Definetly gonna replace the piston while hes at it tho.

[BC3]

If you have ANY popping out of gear issues...Do yourself a favor and replace the fork along with the gears ......I'm surprised it doesn't have witness marks from the side load.....(Bent fork)

[grayracer513]

+1. The fork bears the entire load of holding against the force pushing the gears apart, and was not designed for that much load. Replace it. That's the 3rd and 4th "pinion" gears (mainshaft), and the #2 fork.

[Mazzeppi11x]

it doesnt pop out of gear ever, but i guess ill do it neway while its apart

[grayracer513]

The snapping, jerking, skipping teeth feel you describe IS the gears forcing themselves apart, out of gear, if you will. Under pressure, they force themselves apart by flexing the fork out of the way. Once apart, the load is off the gears, so the force pushing the gears apart is gone, and the fork then forces the gears back together. Unlike most car transmissions, a fork shifted by a cam cannot be pushed back to a neutral position, so your bike can't "jump out of gear" the way cars do, but the same thing is happening in principal.

[Mazzeppi11x]

so everything i need (3rd gear, both 4th gears, psiton, rings, wrist pin, clips, timing chain, shift forks, and new spark plug) would have cost me 485 bucks, but with my mechanics employees discount.....260!!! lovin it

[grayracer513]

You may not need the 4th "wheel" gear (output shaft). It does no shifting. You will want to check the condition of the locking lugs on the 4 other gears that have them, though.

Be sure you replace the left main shaft bearing while you're in there, at the very least.

[Mazzeppi11x]

ya didnt put that in , bearings gettin replaced, and everything else is good. I trust my mechanic, hes always built killer motors for me : )

[426 NOOB]

ya didnt put that in , bearings gettin replaced, and everything else is good. I trust my mechanic, hes always built killer motors for me : )

while the motors apart, dont forget to do a cam chain. Thats always a good idea.

[Mazzeppi11x]

ya at first it wasnt gonna get done, but when i got the invoice and was looking up the parts that were ordered, that was in there. there were quite a few things i didnt need per se, but they were good to do while it was split. I cant wait im ganna have a new motor!!! (basically)