KDXRIDER.NET

Hi !

My '02 KDX is very squirelly at high speed, compared to my '01 XR 200. I'm a 150# beginner trail and dualsport rider, and I'm wondering if I should switch to a lighter set of springs. I was riding sandy dirt road in east Texas. The handlebar would wobble when I go over even just a little bit of sand. The first time I felt it, it scared the jesus out of me because I thought it was about to go into tank slapper mode and I was going to highside. I had to scoot my azz way back and be ready to gas it. On the other hand, my XR was super stable; I don't know if the previous owner did something to the XR suspension or not. I was told by an ex-enduro racer that wobblying is normal, but I'm skeptical about that. I was riding with people on KLR 650 and WR 250 with dualsport tires, and they fly around those sandy dirt and gravel turns. I rode the same route last year on my XR, and I was in the front of the group most of the time and was commended for riding so fast with only a 15 HP. I had to hold the throttle wide open to keep up, but the handling was solid stable. THis year, on my KDX with 35 HP, I was way back in the pack, couldn't keep pace because the steering made me so scared. What should I do? Would softer springs help? Would lowering link make it more stable? I don't ride the trail much on the KDX, it's pretty much relegated to dualsport duties.

I now have...
[*] 0.4 fork spring with 5mm preload
[*] 4.8 shock spring in the back with 4" race sag
[*] Kenda dualsport tires

There are a few things that may help. The forks ought to be flush with the tops of the triple clamps. You might try reducing preload on the rear to drop the back end a bit. You could try reducing tire pressure a bit.
The KDX has a pretty steep steering angle and short wheelbase. I know mine was never as stable at speed as the XR's I had. I had an '87 200 and a '98 400. The KDX was all right, though. Maybe you just have to get used to it?

sounds like it needs a steering stabilizer. steeply picthed forks(kdx) dont have a tendency to wobble at higher speeds. steering stabilizers can fix or dramaticaly reduce this.

What worries me is that there was not much loose sand when my KDX was wobblying. It was mostly packed by recent rain. Last year was a lot looser sand. I'm afraid the bike will do a tank slapper when it hits a big pile of deep loose sand.

By the way, the fork race sag is 2-inches. Is that too much?

Dirt bikes generally aren't overly concerned with front fork sag, general rule of thumb is like 20-30% of travel (or about 50-60 mm ~2 inches). Rear shock is the most critical and will help you determine if you're using the right spring or not. From what you've said you're in the ballpark. The other comments all have a lot of merit as well...tire pressure can make a big difference, and steering stabilizers are a godsend on the KDX (pretty much on any offroad bike). Other things like making sure your front end is not tweaked help.

I don't ride the trail much on the KDX, it's pretty much relegated to dualsport duties.

Kind of what it was designed for, not taking it on the trails is like only wearing your Air Jordans in the living room

Lol. Just read my post. Stupid auto correct! I meant steep pitched forks DO tend to shake at speed.

Indeed. The KDX was certainly built with trail riding in mind. It is not set up for dual sporting. Of course, it is a very versatile machine, and you can pretty much set it up to do whatever you want. Already some good tips here. A fork conversion helps a ton, and even a half ass attempt at balancing the wheels will help. Steering stabilizer, yes. But, make sure your suspension is suited to your weight and conditions before you bother with that expense.

Looking back at the fork spring change I did, something isn't right. I replaced the fork spring with a XR400 one (0.40) and used 5mm preload as recommended here. But I recall the stock spring (0.36) had a bunch of preload. I recall having to compress the spring a whole lot in order to install it. So it seems my front end might be sitting lower than stock geometry because it has so little preload...is this correct? Should I add more preload to raise the front end?

The stock spring is much shorter (like 50mm) than the XR spring, which is why the preload spacer was so big. 5mm might be a little low, maybe 10-15mm of preload at your weight on the XR springs will stiffen them up and may help...of course it's all subjective too The good thing about KDX preload is you can use 1" pvc to make your spacers and cut as many as you like, the hardest part is popping off the cap and dropping the new spacer in. For about a dollar and a trip to home depot you could make a whole mess of different sizes and give them a try

FWIW I found on my bike that when I was undersprung the front end pretty much did what it wanted at speed, got better when I sprung it right, and should get a lot more better (is that proper english?) when I finish m hybrid