Yamaha forks

[kawagumby]

Hi,
I just did another USD conversion on a pristine 97 kdx 200 I recently picked up. I used the forks off of a 2004 yamaha 125.

The yamaha triples work great, you need to knurl the stock kdx stem about .005 to get it to be a very tight fit. You also need to weld a wider stop to the bottom of the stock stop to keep the tank safe from hits. The height is good with no need for a spacer vertically, but as usual, you need to shim up the upper hole diameter as the stem is a little undersized. I use thick toss-away aluminum pizza pan metal to the make the shim - it fits tight.

I used the KDX brake ass'y by changing out the caliper mounting bracket for a yamaha unit. That's the part that looks the same on all bikes but has subtle bolt location dimensional differences related to each manufacturer's take on fork design. When you get oversized rotors, that's the part that moves the caliper out. The calipers themselves are virtually identical so the yamaha bracket works perfectly.

Down below I used a KX wheel with a KDX rotor - if you want to use a KDX rotor you need to tap out the mounting holes to the larger size the KDX uses. I did this because the KDX rotor was like new. The axle is yamaha with spacers made for positioning the KX wheel to center the rotor in the caliper. Obviously, if you have a yamaha wheel that will work too with no spacer mods.

Yamaha forks have better base valve assy's than Kawa for off-road use (IMO) I've worked with both and it took only removing two shims from each of the yamaha base valves to get it to work great for trails. They have larger flow holes than the KX units I've farted with.

On top I use TAG 1/18 bar adapters to get the needed bar height to clear the fork tops (a little over an inch above the triples) which also has the benefit of making the bike more comfortable to ride IMO. It feels a little front high but it isn't, the bike turns great and flys level off of jumps and lands with confidence-inspiring handling.

Just finished my second ride and they are dialed. I never even rode this bike with the stockers.

[dfeckel]

Good info on the Yama-swap. Thanks. Have any pics?

[kawagumby]

Sorry, I don't have a picture site to use, but everythings pretty much straight forward.

[kawagumby]

I almost forgot to add an important detail. On earlier yz's and wr's the upper triple clamp handlebar mounts are too far back, making it difficult to turn the bike easily (hard to get your weight forward quickly enough). It would be best to stay with 2001 and later upper triples if possible or get an aftermarket top. To be honest, I can't remember the year they moved the bar clamps forward, but I know the 2001 and later were good.

[kawagumby]

Here's some details on the fork setup using what I assume to be stock 41 kg springs (feels like it).
no mods to the mid valve
compression stack as follows:

24 .15
24 .15
20 .15
16 .15 crossover
22 .15
20 .15
18 .15
16 .15
13 .15
11 .3

None of these were in the modified stack that came with the forks.

500 ml of 5 wt fork oil makes for about 120 mm fork level

The forks are set up in the triples 1-1/8 inch from the top of the triple to the top of the fork cap (not the nut).

I'm getting full travel with this, a little less than an inch from the bottom casting, and about a quarter inch clearance from the top of the tire to the fender.
This gives a compliant but fairly resistant set of forks for the agressive woods rider IMO. I experienced just a hint of headshake on one fast nasty downhill, so I think the geometry is pretty good for woods too, it turns well, like a typical KDX, steering with the back end.