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06 YZ450F Shifting Problems!!

15 posts in this topic

My 06 YZ450F is having problems shifting from 3rd to 4th. During a race it gets stuck and will not shift into 4th gear. I can stand up and put all the pressure in the world on it, but it will not shift. Then after trying for a while sometimes it shifts. I bought the bike brand new. I had the same problem about a month after getting it. I adjusted the clutch and it seemed to go away. Now it is back. I have always used yamalube. I recently changed to amsoil. It seems to be worse when the bike is warm and under power. If the bike is cold I can start it up and go around slow and it shifts fine. Also, I can shift it fine on a stand. When I take off at the start and go into 3rd it is fine, but then going to 4th it sticks. I kept thinking is was something I was doing, but I have been riding it for 2 years now and not had the problem except once right after I got it. I read the thread about a bearing being bad and changing it out to and 07 one. I am going to check that and do that. Does anyone else have any suggestions of what it could be?

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try changing the clutch cable and perch, but for sure do cet bearing

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try changing the clutch cable and perch, but for sure do cet bearing

Hopefully I will get a chance to take it apart today and will know if it is that bearing.

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I have taken it apart and I do not think it is the bearing. The bearing works fine. I see what the problem is but do not know why it is doing it. That bearing rolls on a drum (looks like a sprocket) with indentions on it. The manual calls it the segment. Each of these indentions on the segment is a gear. In between each indention is a lobe. I can see on one of the lobes is neutral. When you shift from one gear to another the bearing rolls over the lobe and into the next indention or gear. It works fine until you shift into 4th gear. When you shift into 4th gear the bearing gets stuck on top of the lobe. This is the lobe between 3rd and 4th. It gets stuck on the 4th gear side of the lobe, but does not drop into 4th gear. You then have to move the shifter back towards 3rd gear. It moves back on the lobe but on the 3rd gear side of the lobe. It does not drop all the way into 3rd gear. Then when you shift it to 4th it will drop all the way into 4th the next time. Something is not allowing the bearing to move all the way over the lobe and into 4th gear. Sorry if I did not explain this all correct. I am no mechanic, but can half way work on bikes. Does anyone have any clue, what could be causing this? I really do not want to split the cases.

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It gets stuck on the 4th gear side of the lobe, but does not drop into 4th gear. You then have to move the shifter back towards 3rd gear. It moves back on the lobe but on the 3rd gear side of the lobe. It does not drop all the way into 3rd gear. Then when you shift it to 4th it will drop all the way into 4th the next time. Something is not allowing the bearing to move all the way over the lobe and into 4th gear.

I doubt the indexing lever/roller has anything to do with this. For one thing, you said:

... I can shift it fine on a stand.
Have you tried rocking the rear wheel while you try to shift?

Are you using the clutch when you shift? If not, are you letting off the gas a bit? It may be more a matter of getting the trans out of 3rd than into 4th. In this case, it could be just normal if you're trying to force it to shift under power.

But if it is hard to shift at high rpm in all gears, you might have a problem with a trans bearing.

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Just an update on this. I was able to get it into 4th on the stand at track. Now that it is home I am even having trouble getting it from 3rd to 4th on the stand. It will go, you just have to play with it.

Grayracer513 - I think you are correct that it has nothing to do with the indexing lever. I noticed something last night. When I try and shift from 3rd to 4th the shift lever does not go all the way up. It stops at about half way through the motion. No matter how hard you pull it will not go all the way up. This is why the lever sticks on top of the segment between gears. Then you push it back down and pull it up and it goes to 4th. I have tried rolling the back wheel back and fourth and nothing seems to help. Yes I do use the clutch. When it happens I have tried everything. I let off the gas all the way and use the clutch and still nothing happens.

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While the right side is opened up, watch how the ratchet elements work. The ratchet engages one of the pins on the shift cam and then pushes/pulls it into its new position. When released, the level must re-center itself, catching the next pin. Does this happen normally?

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From what I see in the yamaha pictures the shift cam is the actual rod that runs through the case that the shift lever sits on. I am not quite sure if this is the answer you are looking for, but it looks like that part that attaches to the shift cam levels back out when you shift it. I am not sure what pin you are talking about it catching. I am looking right in area where the shift cam attaches to the lever and then attaches into the segment. When you have it in neutral the segment stays loose and does not engage. When it gets stuck in gear, it is doing the same thing. I am not sure if I explained it correct, but the inside of the segment looks like it does when it is in neutral.

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This is a pic of it when it is stuck and will not shift to 4th.

<a  href=dsc01671gn4.th.jpg' alt='dsc01671gn4.th.

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This is a picture of the outside of the segment when it goes into gear.

<a  href=dsc01673vy0.th.jpg' alt='dsc01673vy0.th.

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This is a picture of the outside of the segment when it does not go into gear.

<a  href=dsc01674ls4.th.jpg' alt='dsc01674ls4.th.

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The shift segment is bolted to the end of the shift cam. The part that wants to back out to the right is the shift shaft.

I confused the issue by describing an older system, and I apologize for the angst. Look at page 4-70 of the manual. The shift lever (which by the way is held in place by the crankcase cover when everything's assembled) is #10. it engages a roller (#13) on the shift lever assembly (#15). This assembly sits on a pivot pin/bolt combo in the center of the segment. The lever assembly consists of two sets of ratchet pawls (#17-19), and the rotation of the assembly is limited by the shift guide (#14). Pulling up on the external lever rotates the internal lever up and back (counterclockwise). The upper of the two ratchet pawls catches a notch cut in the segment and rotates the cam to engage the next gear, stopping when the internal lever hits the stop peg on the shift guide plate. Releasing the external lever should allow the centering spring (#12) to return the lever to the at ready position, and moving it either up or down should cause a ratchet pawl to engage the segment and rotate it.

Try to see what is causing the stoppage at 4th gear. If you cannot see anything in the area of the segment and internal linkage, remove the internal lever assembly and shift guide plate, and try to use a deep socket on the pivot bolt to rotate the shift cam through the gears. If it won't engage or shift past 4th to 5th from there, the problem is internal, possibly involving a damaged shift fork or cam.

Be advised: Sweep the floor and move the drip pan before you remove or reassemble the internal shift lever/ratchet/guide plate. It will generally fall apart 2-3 times as you work with it, and you don't want to loose parts.

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I can't be certain, but it looks like there is something under the shift lever pawl in the last picture. If so, that could be your whole problem.

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