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bmxchamp00

5th gear slipping?

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So my 426 is now running great, but of course there has to be another problem. All gears 1-4 work perfectly, but I get into the 5th gear and it doesn't run right. It feels like it bogs down a bit then shoots forward and repeats that until I get tired of riding it. I have been told it is transmission problem, so should I try to swap it with a friends bike which is used for a parts bike? (The same 426 as mine) or bring it in to rebuild? Not worry and don't use 5th gear???

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It's a trans problem.  If it's 5th doing this, then the trouble is specifically that the lugs on the sides of 5th and third gear on the main shaft are worn out and rounded to the point that instead of holding together under a load, they push each other apart, causing the jumping, lurching slip/grab sensation you feel. The shift fork that moves third will also be bent and need to be replaced.

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Exactly what grayracer has said, 3rd and 5th lugs are rounded over and the shift work will be bent. I have 2 yz426f transmissions in my scrap bin that are both like that.

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It's a trans problem. If it's 5th doing this, then the trouble is specifically that the lugs on the sides of 5th and third gear on the main shaft are worn out and rounded to the point that instead of holding together under a load, they push each other apart, causing the jumping, lurching slip/grab sensation you feel. The shift fork that moves third will also be bent and need to be replaced.

So I can easily swap it out with another 426 tranny?

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You can swap it with another 426.  Some people call that easy, and some don't.

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You can swap it with another 426. Some people call that easy, and some don't.

Is this problem going to get worse if I keep riding it like this? Will the 1-4 gears soon be doing this too??

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Possibly.  Can't say without a physical inspection, of course.  Bear in mind though that the engine and gear box share the same oil, so any metal debris the trans dumps into it runs through the system.  Presumably, the filter would catch most of it, but...

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