CR500 front fork swap to 250R *** UPDATE ***

[Derrick Adams]

It's time to finally start on this project. When I first got "Casper" I did a CR500 rear shock conversion. I ended up with over 12" of rear wheel travel and with the use of an Ohlins shock and custom spring, a much better functioning rear suspension.

The goal with the front fork swap is to gain as much suspension travel as possible without raising the bike so much that it's tippy. In preparation for these forks I previously added a custom 10" Douglas wheel with a 21" front tire. So, I effectively dropped the front of the bike 1.25".(difference in height between original front tire and new one)

So the goal is to end up with a ride height approximately 1" taller than original. I may end up modifying the forks internally to remove an inch or so, but hopefully not. We'll just have to see how it pans out. If I can get away from that, I'll end up with 12+" of travel in the front suspension too!

More importantly than the travel though, is that i'm after the larger diameter (stronger) forks. In MX the stock forks tend to flex alot under landing from jumps. To the point of the front tire actually hitting the pipe. (I've seen it with my own two eyes!)

So here's where i'm at so far:
250R triples are modified to accept the larger diameter forks
Front wheel and tire is ready
Front forks are modified to accept 250R axle assembly

Basically i'm down to fitting them on the bike and building the mounts for the front brakes. I'm going to use the CR500 front brake system, since the original 250R front brake line won't be long enough for the new forks, and the CR line is braided steel. The front brake calipers appear to be the same on both bikes.

[Derrick Adams]

Here's the pictures of what i'm up against.

First pic is the distance from where the top clamps fall in original positions.

Second pic is how i'm running the forks now to compensate for the shorter tire. As you can see, i'm looking at around a 3" difference from where I started. I'm thinking of installing some shim stock in between the forks and top triple so I can run them about 2" out the top of the triples (CR forks are tapered between the clamps). This should get me real close to my goal!

[Dusty]

well that sounds awesome....howd you have to mod the trees to accept the 500 forks....

[Derrick Adams]

I just had them bored out to the larger diameter of the forks.

[toyota200x]

Awesome project. I can't believe how much longer those CR forks are.

[Derrick Adams]

I'm finally getting around to doing this install. I did find something interesting tonight. I took the fork cap off the 500 forks and low & behold there is a factory 3" spacer installed in the forks. I pulled that out, reinstalled the cap, bled the air out and WALAA! Now it is approximately 1" taller than the stockers. Now that i've discovered this, I can fine tune the height internally.

What I really need to do though, is figure out a permanent stop for the forks for going UP. That way I have some spring stiffness adjustability.

I'll have it back together by this weekend, so we'll see how it turns out.

[MTS]

How much did you have to bore out the 250r tripples? Im wondering if there not going to be too weak Now that you removed so much Meterial and might crack/snap them on a MX track......

[MyMistress86R]

How much did you have to bore out the 250r tripples? Im wondering if there not going to be too weak Now that you removed so much Meterial and might crack/snap them on a MX track......

I've seen them in person and there appears to be plenty of material left for a solid mount. You'd be surprised how much got taken out, but how much is still left.

[Derrick Adams]

Finished up all the triples last night.
I'm putting the 350X front end on my 500R, the 250R front end on the 350X, and the 500R front end on the 250R. SOooo, I had to press out and swap all those stems around to do it. On a side note, something interesting is that the 350X has a .020 larger stem diameter than the 250R and the CR500. That made things a little interesting, but it all worked out.

I'll be installing the forks tonight and posting some updated pictures. Still have to build the brake mounts.

[Derrick Adams]

Here's some pics of the forks installed. I still have the brake left to do.

[KZXT650]

How much did you have to bore out the 250r tripples? Im wondering if there not going to be too weak Now that you removed so much Meterial and might crack/snap them on a MX track......

Hey, it's a cool idea and i dont want to rain on your parade , but I dont want to hear that you got hurt either. The factory leaves the amount of material they do around the fork tubes for a reason and there was that comment about the forks flexing to the point of the tire hitting the pipe. Just be aware of the EXTREME pressures being applied in MX jumping. I personnally have contemplated the notion of larger forks in a trike tree, and have concluded that it would be best to use a custom billet steel lower clamp with billet aluminum upper and keep a good 5/8" or even 3/4"material all around the uppers and 3/8 to 1/2" on the lowers.
On the note of ride height you can always choke your longer forks as you did up in the tree to adjust it some to keep a larger front tire.
I hope it does work out safely for you , it looks killer to see beefy forks like that there.