03 yz450f ?ions


2 replies to this topic
  • PJ242

Posted November 30, 2009 - 07:39 PM

#1

Ok thought i had a tranny problem. 4th gear and once in a while 3rd the bike was jumping hard like the chain was skipping teeth, but wasnt. So I had the case split and really couldnt find nothing wrong in the tranny beside the fork that locks in the gears. It had wear on it like it was rubbing off something. We couldnt tell if it was bent to the eye. Anyway we went ahead and ordered a new fork. We also ordered a timing chain while we are in there. Does any 1 else have a idea of what it could be before we put her back together?!

Also we went ahead and and ordered a high compression (13.5) Pistion and rings. Was that a good or bad thing? Its going to get honed and a clean up port job too. The valves looked good. Any thing else I should do to the bottom end while I have it apart?

Also noticed my sub-frame was bent so I have to start looking for one. IS there anything else on the 03-05 450f that are common problems?

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  • grayracer513

Posted December 01, 2009 - 07:05 AM

#2

Ok thought i had a tranny problem. 4th gear and once in a while 3rd the bike was jumping hard like the chain was skipping teeth, but wasnt.

The fork does not lock the trans in gear, it only shifts it. What holds it in gear under a load is that there is a slight undercut on the locking lugs and/or slots on the sides of the gears so that when a load is applied, they hold against one another. As these lugs become worn and rounded over, the undercut becomes reversed, and the two gears push away from each other when power is applied. The fork becomes bent as a secondary result.

You will need to identify the gears involved with the third and 4th shifts and replace them, along with the two shift forks involved. In this case, that would be all four gears of the 3rd and 4th pairs (the middle two on each shaft), and both forks. Check the condition of the lugs and slots on the other two gears tha have them, too.

  • PJ242

Posted December 01, 2009 - 08:26 AM

#3

The fork does not lock the trans in gear, it only shifts it. What holds it in gear under a load is that there is a slight undercut on the locking lugs and/or slots on the sides of the gears so that when a load is applied, they hold against one another. As these lugs become worn and rounded over, the undercut becomes reversed, and the two gears push away from each other when power is applied. The fork becomes bent as a secondary result.

You will need to identify the gears involved with the third and 4th shifts and replace them, along with the two shift forks involved. In this case, that would be all four gears of the 3rd and 4th pairs (the middle two on each shaft), and both forks. Check the condition of the lugs and slots on the other two gears tha have them, too.


When it comes to trannys i'm lost. I just tried to explain what the guy at the machine shop told and showed me when he asked me to come over. But now you edjucated me on it a little bit and i'm gunna call him up before he put it together and ask him about the lugs





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