hesitating on 4th gear - YZ450F 2004

dear guys,

 

I am rebuilding a YZ450F and everything is OK, but a transmission.

it felt perfect on 1, 2nd gears, but slight hesitation on 3rd and worst on 4th gear.

 

It feels like clutch keeps ON & OFF as frequency.

It accelerates and but still hesitating.

 

I tried to remove TPS, and gonna lower clutch disk numbers (I put as many as it can take).

 

I checked condition of transmission gears when it engine was open. But everything and every gears' condition was mint.

 

 

Please help.

What would be the cause???

What should I do?

WHat should I check next?

Clutch slipping?

Worn gears.  How badly the jerking "hesitation" is depends on how much load you put on it, right?   The locking lugs on the sides of the gears have lost their proper squareness and become rounded over.  When that happens, the gears force away from each other instead of binding together.  When the condition gets bad enough, they bend the shift fork over far enough to skip out to the next slot, where the fork slams them back together, repeat.

 

If this is happening to both third and fourth, you will need both shift forks, and the third and fourth gears for the main shaft and output shaft.

Worn gears.  How badly the jerking "hesitation" is depends on how much load you put on it, right?   The locking lugs on the sides of the gears have lost their proper squareness and become rounded over.  When that happens, the gears force away from each other instead of binding together.  When the condition gets bad enough, they bend the shift fork over far enough to skip out to the next slot, where the fork slams them back together, repeat.

 

If this is happening to both third and fourth, you will need both shift forks, and the third and fourth gears for the main shaft and output shaft.

Thanks to you, being here, still helping, Grayracer.

I googled for the problem solution for hours. And everywhere the problem occurred, you were there.

 

I found out what is wrong with it while reading your replies.

I am gonna check the gears soon.

As I remember, Gears were in mint condition, but forks. I think the forks must be bent.

 

After the inspection, I would replace damaged parts.

 

Anyone tell me part numbers of 3rd and 4th pinions and relating fork???

You're having this problem with 3rd also, right?  If so, you need the 3 & 4 on the output shaft as well, and the other fork.

You're having this problem with 3rd also, right?  If so, you need the 3 & 4 on the output shaft as well, and the other fork.

I am gonna part apart my engine this weekend to see what was damaged.

before the taking it apart, I should check 3rd gear again.

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