Fork compatability

I came across a 2005 YZ250F supermoto that someone is parting out. What would it take to fit the forks/shock to my 2003 WR450F? It includes a nice set of triples that I'd be happy to swap, would I need to play with wheel spacers, caliper mount, etc? How about the shock? Is there anything else I should look into getting from it?

That fork will bolt directly onto your bike, accept your brakes, wheel, axle, and most everything else.  (The brake hose routes differently.  You'll want one) You need to use the clamps it came with, however, and that might cause you to have to re-work a thing or two like the headlamp mounting.  While it should be the same, check the length of the steering stem compared to yours.  If it is significantly different, press it DOWN out of the "new" clamp and press yours in its place. 


The '05 fork was not a great fork, but it's way more than a notch or two better than the '03 fork, and it can be worked with.  The shock I would only be interested in if it was in much better condition than my own, or to have a spare to fiddle with.  Except for valving, there's not much difference in them.

I believe the bike has been set up well for supermoto, including springs/valving. Regarding the shock, is it at least compatible enough that I could fiddle with it without taking the bike out of commission? 


Is the spacing the same? Meaning will my wheel with spacers work in the new forks? I don't have a speedo drive, they're aftermarket wheels without one.

Or could I swap just forks without a problem?

I missed that you said I'd need to use the new clamps. I measured and it's significantly different diameter. I guess I'll need to find a press and swap steering head bearings. Is All Balls good, or should I go for something else? This bike sees mostly street use, so I don't mind if it just barely increases effort to turn the bars quickly (and the new triples likely have different offset anyway).

The stem will only vary in length, if that.  You will probably find that it's about 12mm shorter.  Otherwise, it will use your original bearings.


The '03 uses 46mm forks, the '05 YZ's used 48mm forks


If you use your axle, spacers, and wheel, yes it all bolts up.

Is the difference in length due to YZ vs WR, 250 vs 450, or year? The bike they came off of was a steel frame. Hopefully shorter stem isn't a problem, if it is I'll find a press. 

The difference is YZ250F vs. YZ/WR450.  The heavier bikes were built with longer stems for strength.  Having made similar swaps in the past, I feel fairly certain you will find the stem too short.  Look at your crown nut and see if you think it will work with a 12mm shorter stem (not).


It's a simple process, no heat involved, although a dab of anti-seize is a good idea on assembly.  Support the bottom of the clamp on the press bed, preferably with something like a heavy tube or a plate with a properly sized hole in it.  Allow clearance through this hole 1/8" larger than the stem so it will clear the retaining ring that keeps the stem from moving upward in the clamp.  Screw the crown nut down flush with the top thread and remove it from the clamp by pressing DOWN.  This will remove the lower bearing at the same time as it removes the stem. 


Reassemble in reverse; invert the whole thing, apply a smear of anti-seize, and press the stem back UP into the clamp from the bottom until the ring stops it.  Reinstall the bearing (or a new one) and you're done.


As little as a ten ton press should be capable of it.

Thanks. The triples are RG3, hopefully they'll accept my stock stem without a problem. 

Related question: I'd like to pick up a set of forks for dirt use, as I doubt the ones I just got will work too well there (set up for supermoto). What year/model forks will slide into my 05 YZ250F triples? I don't want to have to swap triples very often.

YZ450 triples are wider, starting year (? 2007?)

Not sure about the YZ250


You have to consider

- steering stem length

- width (tube spacing)

- wheen spacers to match the wheel you use

The wider spacing came in with the SSS fork in '06.  The fork tubes were moved 2mm farther apart, but the axle lugs were moved inboard 1mm each so that the wheel spacing and axles stayed the same.  I think that the '06 and '07 YZ450F fork and the same model YZ250 or YZ125 fork will fit the '05 clamp, and if they do, then so would the '06 YZ250F fork (the '07 YZ250F uses the aforementioned smaller caliper/master setup). 


Using any of the SSS forks in the '05 clamps will cause the front wheel to be moved 1mm off center to the right.  The fat end of the axle will stick out of the right side lug about 2mm when the forks are aligned, too. As long as this 1mm shift does not cause any problems with the alignment of the caliper and rotor, you can compensate for it either by shaving the extra MM off the left (brake side) wheel spacer, or by pulling the rim over with the spokes.  I know of at least one desert racer here locally who just ran it that way (shifted right) with no apparent problems, though, too.

I have a mini lathe so it shouldn't be too hard to turn down a left side spacer if that's the best solution. Is there a specific year/model of forks that should work better/worse for trail riding? I'm 185lb + gear. 


I don't particularly mind a smaller caliper/master if I'm swapping forks anyway - the supermoto setup has a 4pot and Brembo radial master, so I can't exactly run it on dirt anyway. The misalignment of the caliper shouldn't be a big problem, I can run some shims if it's a problem. 


Thanks for all the advice. I'm looking forward to putting the 05 YZ250F forks on the bike tomorrow.

I ran my WR with the right shift for a year, and when I just corrected it, I really noticed how much better it felt on the street.....even with the same tires..

Are the newer forks better, or is it just that I'm more likely to find them?


Also, what do I have to remove to swap the shock? I'd rather use the one that's been resprung/revalved for supermoto, and matches the new forks, but don't know how much work I feel like doing.

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