Transmission issues on 2008

I have a 2008 YZ450f with 121.7 hours. I change the oil every 6-8 hours with Amsoil MCF (10w-40), and use a Scotts stainless oil filter which I clean every time. I have never noticed an abnormal amount of metal shavings or parts in the oil filter. I'm not extremely hard on my bike and I don't believe I have any abnormal habits while riding that would lead to a trans issue or even a possible future failure.

I noticed a few months ago that when shifting from third gear to fourth gear the trans popped out of gear temporarily, then went back in. Then about a month ago I noticed the bike pop out of gear again once or twice. I did a desert race two weeks ago and it popped out of gear twice, and finally earlier today at a GP the bike popped out of gear 2-3 times.

It sounds like I have a bent shift fork which could be causing the splines on the transmission gears to wear abnormally( which would explain while the problem is getting worse). Does this sound like a descent assumption?

Also, this may be a good time to look into putting WR gears into my bike. If anyone has any feedback that would be helpful. ( I've searched through various threads about this topic, but feel free to input:thumbsup:)

One more thing...If anyone has a good recommendation as to where to buy parts please feel free to post as well.

Edited by jim513

It sounds like I have a bent shift fork which could be causing the splines on the transmission gears to wear abnormally( which would explain while the problem is getting worse). Does this sound like a descent assumption?

It's usually the other way around. The splines have nothing to do with it, though. The locking lugs on the sides of the third and fourth pinions become worn so that they don't hold in the way they are supposed to. That progresses to the point where they push away from each other, and finally to the point where they force the fork to bend far enough to let them jump from one lug to the next. Eventually, the fork is bent too.
It's usually the other way around. The splines have nothing to do with it, though. The locking lugs on the sides of the third and fourth pinions become worn so that they don't hold in the way they are supposed to. That progresses to the point where they push away from each other, and finally to the point where they force the fork to bend far enough to let them jump from one lug to the next. Eventually, the fork is bent too.

I wasn't quite sure, so thanks for clearing that up:thumbsup:

Is there anything abnormal that would cause this, or is this an issue that just can happen over time?

IMO, the two things that would most likely lead to this are simple accumulated time, or "lazy" shifting. That is, failing to shift from one gear to the next quickly and cleanly, allowing the gears to clash briefly as they engage, and/or loading the gears before they are quite fully engaged.

It's usually the other way around. The splines have nothing to do with it, though. The locking lugs on the sides of the third and fourth pinions become worn so that they don't hold in the way they are supposed to. That progresses to the point where they push away from each other, and finally to the point where they force the fork to bend far enough to let them jump from one lug to the next. Eventually, the fork is bent too.

This was the issue, but it was less severe than I thought it would be. The locking lugs were just starting to round, and I mean just barely. The shift fork wasn't bent severely if at all ), but was just beginning to wear unevenly on the area where it contacts the gears.

Thanks for the help.:banana:

By the way, (without a discount ) I found cheapcycleparts.com to be the cheapest place for OEM parts.

Cycle parts warehouse is cheaper than cheap cycle parts, BUT go with the TT store. They will price match any reputable store.

Thanks for the info. I was hoping to but WR gears in my bike, but 3-4 of the gears are on national back order, and no one seems to know how long:banghead: I was informed that Monday they would know more about the situation with the back order. Does anyone know anything about this?

I found out today that all the gears but the 2nd pinion will be available next week. The 2nd pinion is expected to come off back order April 1st, which will get me all the parts around the second week of April.

To anyone who has done the WR tranny swap, is it worth a month of no riding?

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