WR + YZ = WR250XYZ

I'm a cheap bastard and I want to see if I can put a 21" front wheel on my WRX (and keep the 17" rear for now) while spending the least possible.

The WR-R/X have a 17mm front axle whereas YZ-F and WR-F bikes have a 20mm axle so it's either a fancy adapter or new forks.

Both the wrr and wrx have KYB 46U forks and (according to Racetech) the guts are pretty much the same as the:

2003 ~ 2004 WR450F & 2003 YZ450F
2001 ~ 2002 WR426F & 2000 ~ 2002 YZ426F
1998 ~ 2000 WR400F & 1998 ~ 1999 YZ400F

After 2004 (2005 for the WR) the YZ went to 48mm forks so those will not fit the triples on our bikes. Also I'm not including the WR/YZ250F or YZ125/250 2-stroke bikes because the spring rates vary more across models and are lower (.44 or .43 vs .46) so it would take work to shim to the desired higher rate (wrr is .46, wrx is .47) and I might have to buy new springs (~$100).

All the front wheels are the same across the models above and the same goes for the front brake: 250mm rotor, same caliper and caliper mount bracket. The WRX has a 298mm front rotor and larger caliper so I'll lose some braking power there but that's ok. With an 80 or 90 mm wide knobby or intermediate front tire more braking power only makes it easier to lock up the front wheel. And if I find out that 250mm isn't enough, there's alwasy 270/280mm kits.

So enough theory, here's how it looks so far: test fitting the forks, wheel, and axle.  

A few guys put wr450f forks on r models, a search should bring lots of info up on it.

You need to make new wheel spacers thats about it if you have the wheel and brakes that came with the forks.

The "guts" are not the same, the other 46mm forks have much larger and better working pistons and shims, the wrx and wrr forks have the same guts as yz 85s.

If you find a set of wr450f forks you wont ever want to put the wrx ones back on.

The 2000 to 2004 forks with YZ250 front wheel, spacer and axles bolt on. No custom spacers needed. You can use the stock caliper but because of the different fork guards, you have to either use the YZ brake line or make a Bracket mount WRR brake line clamp.

Biglake wrote:

A few guys put wr450f forks on r models, a search should bring lots of info up on it.

You need to make new wheel spacers thats about it if you have the wheel and brakes that came with the forks.

The "guts" are not the same, the other 46mm forks have much larger and better working pistons and shims, the wrx and wrr forks have the same guts as yz 85s.

If you find a set of wr450f forks you wont ever want to put the wrx ones back on.

Damn, that's actually correct: according to RaceTech the valve kit for the YZ85 (FMGV 2040) is the same as our bikes (FMGV 2040), where the WR/YZ have a different valve kit (FMGV 2830)

4play wrote:

The 2000 to 2004 forks with YZ250 front wheel, spacer and axles bolt on. No custom spacers needed. You can use the stock caliper but because of the different fork guards, you have to either use the YZ brake line or make a Bracket mount WRR brake line clamp.

That's what I did: stock YZ forks, wheel, caliper, etc. Pretty much plug and play.

Here's an update on progress, after compeletely disassembling the forks and cleaning the everything, I started reassembly with new seals and oil.



Custom seal saver:



Fork length comparison (WRx vs YZ): 57mm overall, 18.44 mm for the outer tubes.


Only thing left to do is to swap front calipers, and the knobby for a K60 and it's good to go.

All done and back together.



Also installed a SpeedoDRD, brake light flasher, and resistor to replace the EXUP motor.