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SB105

2007 YZ 450f 4th gear issues

5 posts in this topic

I got a problem with my 4th gear, my 4th gear just simply doesnt work, being in 4th is basicaly just like another neutral for me right now. I took the engine apart hoping to find an obvious problem but now that everything is apart im not sure what the problem is. It seemed like the outer circlip holding the 2nd pinion gear had snapped out of its groove because when i pulled the set of pinion gears out, the 2nd pinnion gear and circlip were apart from the rest. Can this be the cause of my problems?.....there is also some wear on one of the shifter forks and the 4 square blocks(i dont no what they're called) that lock the gears together between the 3rd and 4th pinion gear have some wear, the square edge is rounded off a bit....

anybody know what i need to do to fix this problem

http://www.ronniesmailorder.com/fiche_section_detail.asp?section=556224&category=Motorcycles&make=Yamaha&year=2007&fveh=12915

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The clip could be why 4th doesn't work. That clip holds both 4th and 2nd from drifting away from the 3rd pinion, which locks to 4th to engage it. As for the rounded locking lugs, you'll need to replace the gears.

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Or if you don't want to spend or don't have anything to spend (like me :thumbsup: ), than you can grind those locking lugs with a dremel multitool (or similar) back to being "square", or better, (as I did with my 5th gear locking lugs), you can give them a slight negative angle. You have to make sure that all lugs engage at the same time, so you can't just grind one of them. Of course buying a new one is simpler, faster (but more expensive :lol: )

Good luck

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I don't advise refinishing the locking lugs by hand under any circumstance because there is no way to ensure that you grind them uniformly within the necessary tolerances. All 3 or 4 lugs must bear the drive load equally if the gear is to be as strong as intended. If one is just .003" larger than the rest, it will carry the load by itself, and may break off because of it.

Furthermore, in recutting the lugs, you may grind through the hard face into softer metal underneath, in which case the gears will wear rapidly afterward. For $50 apiece, I don't think it's worth it.

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False neutral is usually caused by gears not holding, ie. the cogs are rounded or a shift fork is bent.

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