Look at these pictures YZ450 gears.. What is wrong with these?


10 replies to this topic
  • llengner

Posted July 21, 2004 - 04:56 PM

#1

http://www.lengner.net/motogears.htm look at the pictures at this link. I cant find a problem with these gears. But the bike would pop in and out of 4tn gear in. feels kind of like chain slap, or when really riding hard (racing) thought I was missing a shift but realized after testing that it was a gear box problem. 4th only...

I saw a number of other posts with similar symptoms but it appeared their problems were all easily identified once they split the cases. I cant really find any problems with mine. One of the pictures shows slightly rounded gear cogs (not teeth but cogs or claws, whatever they are called) but nothing that would seem to cause major problems. Anyone have experiences in this? Do I replace everything or what?

  • John_Lorenz

Posted July 21, 2004 - 05:24 PM

#2

scoring on the forks should not occur like that. The fork is bent, or the shims are shot. You need to spec the shims make sure they are in tolerance

On the fork the only real way to tell is to do one way I know of, Stare and Compare with a new .

This link will bring up the parts Fitch form Yamaha
web page

  • Hamish

Posted July 21, 2004 - 09:13 PM

#3

the dog tooth is rounded off. And that fork is well and truely stuffed :thumbsup: Guarenteed to jump out of gear.

  • jimmyg

Posted July 22, 2004 - 02:21 AM

#4

i would replace the gears on both sides of the shift fork & the shift fork it shouldnt be scuffed like that a sure sighn its bent.

  • llengner

Posted July 22, 2004 - 05:51 AM

#5

Thank you all for the help.
Can anyone answer some additional questions. Why would a fork all of a sudden get bent. I have had the bike for 2 years. I have not fallen anytime recently. I am almost wondering if the score marks on the fork were not caused by me pulling the thing apart. They look very rough and very newly created. I would figure if the scoring was caused while riding that it would be very polished and I would have seen corresponding scoring on the adjacent parts. But I see none of that. The dealer said when replacing gears always replace the opposite gears too. I am thinking about replacing both forks and all adjunct gears. Any comments on this? What about the drum? The dealer said if the drum is worn it would cause the forks to be bent. I cant see that my drum looks worn. Any ideas?

Lastly. A gasket kit. Dealer said 175.00. That sure seemed like a lot.

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  • sparks426

Posted July 22, 2004 - 09:05 AM

#6

The fork being bent would not necessarily have caused the problem. The forks place the gears in the correct position, but the dogs have to be square to each other to help keep the gear in position. Since the dogs on the gears are worn, they put additional side pressure on the fork. The fork gives slightly due to this extra pressure, allowing the gears to seperate enough to jump out of gear. The wear on the fork is definately not from you spinning it by hand, but from the side of the gear when it jumps out of gear.

The $170 for gasket kit sounds out of hand. There is no center gasket, so you should only need head, base, and side case gaskets. Unless the kit includes all the oil seals too, but I would call around. Good luck!

  • Hamish

Posted July 22, 2004 - 09:47 AM

#7

Since the dogs on the gears are worn, they put additional side pressure on the fork. The fork gives slightly due to this extra pressure, allowing the gears to seperate enough to jump out of gear. The wear on the fork is definately not from you spinning it by hand, but from the side of the gear when it jumps out of gear.



I'll second that :thumbsup:
When I did my tranny I was able to reuse all the gaskets except for the base gasket which was under $AU15 from memory. If the head gasket hasnt been leaking and still has a raised ridge you can safely use it again.
Head gaskets are good for a few removals

  • MXKyle

Posted July 23, 2004 - 03:23 AM

#8

Sparks is right. The damage to the shifting fork is the result of an already worn gear. When the dogs on the gear get worn such as yours they will not engage under load. The shifting fork exerts a lot of force trying to get the damaged gear to engage anyway and the result is that the oil isn't enough to keep the contact area on the shifting fork from burning up. I seriously doubt that the fork is bent. It’s just smoked but it still has to be replaced. :thumbsup:

This is very typical of almost every transmission problem I have repaired since Honda came out with the Ellsinore. Don't spend too much time worrying about it. It is normal wear and tear on any tranny. If all the bikes of a particular model are having problems it is generally a metallurgical problem with the gears. For years Suzuki would have a new part number for harder gears within three months of releasing a bike.


--KT--

  • crf450f

Posted July 23, 2004 - 08:08 AM

#9

Your Dog gears are slightly rounded! I had same issue.
Look for rounded edjes on the dogs, if they do not have sharp corners, than it will slip out of gear, and cause chail slap, especiallly when putting a load on the bike.
This happened to my 426. It would slip out of 4th, and chain slap. Just a suttle rounding of the dog grooves causes this. I changed the 4th and 3rd dog and issue was gone!! Get new gears!!! Problem solved.

  • yzf450jack

Posted July 25, 2004 - 04:54 PM

#10

llenger i still have my 4 speed for sale you can't go wrong just drop em in and go :thumbsup:

  • llengner

Posted July 26, 2004 - 11:07 AM

#11

llenger i still have my 4 speed for sale you can't go wrong just drop em in and go :thumbsup:


I believe I was bidding on them on eBay?? If so the $200 was a bit much for the parts I thought. I still had to have them shipped and then worry about any possible damage that may not have apparent to you but I would inherit once installed. Besides I paid a bit less than the $200 for new parts at the dealer. both forks, some shims and spacers, necessary gears etc. I am sort of a "buy it new" kind of guy. I'll buy something used from time to time but want a screaming deal when I do. Thanks for the advice and the offer however..





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