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Sturdy40

2003 YZ 450 F Trans. 4 speed

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Hello: anyone

I have a very clean 2003 YZ 450F With a 4 speed trans. and want to put a2006 YZ 450 5 speed trans in its place. Is this possible?

Thanks: Steve

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Won't fit in the cases you can use a wr trans and fit yz250 gears to get the same ratios

but it pretty high$$ if you put in all new stuff you could have a grand in the trans.

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Just use the 4 speed. Stock it'll do 85MPH. The gear spacing is wider using a 4 speed, but its a 450 for God's sake. Get used to it and run it. Add a flywheel to minimize stalling.You probably wouldnt like a WR gearbox since the 4th and 5th gears are really wide, at least I didnt. I loved my 05. Raced in the desert and gp's without an issue or ever wanting more. Now my RM 250, that is a different story.It could use a different set of ratio's.

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The '06 trans is 12mm too wide to fit. You can use the '03-'06 WR450 5 speed as a bolt-in replacement, though. the WR trans is a wide ratio, and it makes a good swap for an enduro or desert bike, as it has both a lower 1st gear, and a taller high gear. To use it, you need the complete transmission, including the shift cam and forks.

http://www.thumpertalk.com/forum/showthread.php?p=2761046#post2761046

I know someone who has installed a YZ426 5 speed in an '03, but it required a considerable amount of trial and error and custom machine work. It DOES NOT bolt in.

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