Difference between YZ426 & WR426 gearbox

Whenever I want to see what’s the same and what’s different between the two bikes, I start by looking up the Yamaha part numbers for a particular part on each bike. I've found that many parts for these two bikes share the SAME part number and some of course are unique to the WR or YZ. For instance, the cylinder part number for an '01 YZ426 is Y5JG-11311-00-00, and for an '01 WR426 is also Y5JG-11311-00-00... same cylinder, same part number. However, the rear fender for the YZ is Y5BE-21611-00-00, and the WR is Y5BF-21611-00-00.... different fender, different part number. Now, I'm not certain its an absolute rule that the same part number = same part, and a different part number = different part, but it would be logical to assume so and I've personally found this to be the case. Seems like Yamaha tries to use the same parts between the two whenever they can, which would make sense from a business perspective as different parts means different tooling to make them, a larger spares inventory, etc..

Anyway, back to the trannys,, I went out to PARTSFISH.COM and took a quick peek at the parts diagrams for the '01 YZ and '01 WR trannys, and it looks all the gears and many other parts do have unique YZ or WR part numbers. Seems strange, cuz I thought I remembered reading something about it being just 2 or 3 of the gear ratios being different between the two bikes,, not all of them. I suppose the two bikes could indeed share some common gear ratios, and use different gears to do it (a 1:2 ratio same as 5:10, but 1 isn't 5 and 2 isn't 10).

What do you think Rich, have you dug through these trannys any??

By the way, when I had a YZ and wanted the WR gearing, I also thought about trying to change trine gearing, but I wimped out and sold the YZ, bought a WR,, and "ZYed" the WR (seat, tank, plastics, suspension, etc..)

Originally posted by hjgird
A budy have a YZ426, but would like to make the gearing like a WR426, without changing the whole gearbox.
1) What is the differences between the gearboxes.
2) Is it possible to change only some of the gears in the YZ gearbox to WR gears.

Click to expand...

YZ
1st - 1.846
2nd - 1.500
3rd - 1.278
4th - 1.091
5th - .952

WR
1st – 2.417
2nd – 1.733
3rd – 1.313
4th – 1.050
5th - .840

Same primary ratio (62/21), final gearing 1 tooth different.

You can change only some of the gears, but that depends on which ones you try. I do know that someone at Thumpertalk.com purportedly discovered that some of the dogs didn’t line up between gears (for example, if you swapped only the fourth gears would the dogs still line up with stock third gear wheels?).

You may try a search on the topic here at DRN and at Thumpertalk as well, because this has come up many times before, and I know that at least one guy successfully changed a few of the gears in his YZ to WR parts.

Hope this helps.