i need help with a tranny idea.

i have a 2003 yz450f, it is a 4 speed...i want to change some things. i would like to make a 5 speed out of the following. 1st gear from a 2006 5 speed transmission, 2nd, 3rd, and 4th gear from my 2003 yz450f, and the 5th gear from a WR450f. will it work? or am i an idiot. HELP?

I dont know about making it a 5 speed, but people with YZ250s will put WR426/450 3rd-5th gears in their bikes. They swap right it. I believe just 5th can also be done. and 1-5 can also be done with alittle grinding of the case. So the transmissions are somewhat swap-able. Not sure about making a 4 speed a 5 speed as there would be alot more than just the gears to change.

The '03-'06 WR450 5-speed fits directly, but only as a complete trans, right down to the shift cam and forks.

Read:

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

The '06 and up YZ450 and the '07 and up WR450 are interchangeable, but they are both 12mm too wide for the first generation 450 cases.

I think you should stick with the 4 speed. You never know what you miss till you don't have it anymore. I had an 03, stupid fast, perfect gearing, and went to a 06 and chased down that magic gearing the entire time I had the bike and still never liked the gears. Now, I have a 2010 and I wish I still had that 4 spd tranny in my bike, heck, maybe even Tim Ferry's 3 spd.

The only difference between the 4 speed and YZ450 5 speeds is 4th in the 4 spd sits between 4th and 5th on the 5 spd. Otherwise, they're nearly identical:

1.929

1.533

1.278

1.091

0.952

1.929

1.563

1.278

1.050

The WR, of course, is quite different:

2.416

1.733

1.312

1.050

0.840

I just liked being able to put it in 3rd and 4th and not worry with 5th.

anyone know where i can get a complete 2003 WR450f tranny???:ride:

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