KDXRIDER.NET

I recently installed klx300 usd forks, changed front wheel bearings and seals, and put new brakes up front on my 02 200. I've noticed that at higher speeds the front wheel wobbles-not side to side, but an up and down wobble like when a tire gets a flat spot on it. It started before the new brake oafs were installed. I've changed fork oil and tightened the stem and fork clamps and run tire pressure at 9 psi but no dice. That wobble is the reason my front tire feels lije it's going to wash out even at straight line riding-but it's noticeable only on the highway. It's been too cold to work on it, but what areas should I look at? It's possible the new bearings suck, but what else do I need to check? I felt no wobble with my old forks by the way. Thanks for any advice!

Is the wheel true? Tire seated evenly all the away around? Balanced?

Dirt bike wheels are so far from balanced with their single beadlock. My KDX needed 6 oz of weight opposite the beadlock just to feel like the tire wasn't hopping off the road at 55 mph. I want to say it took 9 oz in the back. Makes a huge difference, but not so much in a "washout" feeling.

How did the fork swap affect geometry? Triple clamp and axle offset? Front ride height? No one ever seems to discuss these things here, which surprises me. Changing offset even 1.5mm or moving the forks up or down 2-3 mm can make a noticeable difference.

Sent via morse code

You might try Motion Pro's lite locks----two of them are lighter than the OEM single lock---and if you locate them 180 degrees apart on your rim they even cancel out that weight. If balance isn't your problem then you might spin the tire and watch it for up and down wobble indicating that your axel isn't centered in your wheel? If you don't see any up and down wobble there then go back to working on the balance-------got to be one or the other? (most likely).
http://www.motorcycle-superstore.com/32 ... PLA1303&WT.

I actually went out after I posted and put my bike on the stand and checked the wheel- it's horribly out of balance. I'll try adding weights first chance I get. The wheel seems true, but my spokes are a mess. New wheels and spokes after tax time!

adam728 wrote:Is the wheel true? Tire seated evenly all the away around? Balanced?

Dirt bike wheels are so far from balanced with their single beadlock. My KDX needed 6 oz of weight opposite the beadlock just to feel like the tire wasn't hopping off the road at 55 mph. I want to say it took 9 oz in the back. Makes a huge difference, but not so much in a "washout" feeling.

How did the fork swap affect geometry? Triple clamp and axle offset? Front ride height? No one ever seems to discuss these things here, which surprises me. Changing offset even 1.5mm or moving the forks up or down 2-3 mm can make a noticeable difference.

Sent via morse code

i also raised the forks about 12mm to put more weight on the tire. I usually run forks flush, but I'll try it this way after I balance my wheels.

Watch out for head shake lowering the front end that much

Actionman wrote:i also raised the forks about 12mm to put more weight on the tire. I usually run forks flush, but I'll try it this way after I balance my wheels.

Are the KLX forks the same length as the KDX?

Tedh98 wrote:

Actionman wrote:i also raised the forks about 12mm to put more weight on the tire. I usually run forks flush, but I'll try it this way after I balance my wheels.

Are the KLX forks the same length as the KDX?

From the center of the axle to the top of the fork measured almost the same using my less than scientifically calibrated yardstick. The attitude of the bike seems also to be the same. My understanding is that the Klx has similar rake and trail numbers to the kdx, but I'll check my manuals later to verify. My wheel is unbalanced as heck though, so I'm actually out right now trying to find some wheel weights. It's odd that I never noticed this with the old forks though. Other than that the Klx forks are pretty good.

I remeasured my fork height in the clamps and I had only raised them 6mm instead of 12mm lol. I also went through the re-tighten procedure for the clamps and front brake/ axle. I'm actuslly on the woods right now testing lol. With the forks 6mm lower, the bike handles 1000% better! I never realized how much better it would be with that tiny amount. Also, it is more stable at higher speeds! I'm assuming I simply didn't have enough weight on the front end to get a good bite. The wheel still wobbles, but it's way, way less noticeable. When I get home ill actually use my tire weights and try to balance my wheel, but for now its a whole lot better. Makes the front suspension work better to boot!

I don't think it's so much a change in weight bias, but a change in front end geometry. Generally, when you raise the fork tubes in the triple clamps, you steepen the fork's rake angle, which quickens up the steering and reduces the high speed stability. Lowering the rear with longer links, or otherwise increasing the rake angle should have the opposite effect. That's why it's important to consider the whole geometry picture when making these kinds of changes.

Seems logical to me. It feels great! Much, much better whatever it is lol.

Are you running the front rim lock? Just a thought. If it is not there, it might throw off the balance.

Yep. I've got the lock on it.

Yeah, moving the forks 6 mm is a big move. You might try 2 mm moves up or down from there and the same with your shock preload. Or you might be thrilled with it the way it is!

This 6mm was the upper limit of how high I was going to raise them. I had previously cut a piece of pipe for another project and slid it over each fork tube and used that as a template to make sure each leg was the same distance in the clamps. It happened to be close to 6mm. What surprises is how utterly stable it is since the wheel isn't moving around as much anymore. I'm sure that when I get the wheel balanced that ill end up lowering the fork tubes again( remember that I said I slways ran them flush) to get back my stability . Man it's been so long since I've messed with dirt bikes that every time I rediscover one of these common-knowledge tricks it seems like a revelation to me lol. I love it how it is right now though; its fun in the woods and I'm a lot more confident with my front end now that the skittish feeling has been lowered a little.

I doubt very much that wheel balancing is going to let you put the forks back to flush and still feel stable. I think you accidently found a front/rear height combination that turns better.
You really do have to play around with shock preload and fork height, in pretty small increments, to find that sweet spot. I usually find a 3-4 minute loop of trail, bring my tools, and tinker with it. You'll know it when you find it.
Once you get the "attitude" how you like it you can start playing with clickers.......A whole different set of issues there....

Finally got around to adding 6 tire balancing weights to the wheel opposite the bead lock. No more wobble. Front end tracks straight as an arrow. I'd never even dreamed of balancing a dirt bike wheel, but it works great!