Hey guys

Couldn't find any similar threads on the forum. Bought a 2006 klx250. When I go over a speedbump the front suspension seems to unweight and slam into whatever keeps it from coming apart? Is this an adjustment or do I need to replace something?

 

Do you know the condition of the oil and oil level in the fork? If oil was too low, rebound damping would be about zero causing a severe top out and probably clunk. There is a rebound circuit in both forks. I'm guessing if one of the forks lost enough oil, the rebound in the other fork probably wouldn't be sufficient to stop a clunking top out. Then again, someone may have been putzing around in the fork and installed a part(s) incorrectly. You're problem sounds like a severe top out or broken or incorrectly installed parts. Do you know if this fork was ever serviced?...and if so by who? If not, it's time to do a tear-down and service anyway for fresh oil, seals, and an inspection. And while it's apart, probably heavier springs are called for unless you're 160 pounds or lighter. If you can't do it, get a knowledgeable, trustworthy mechanic to do it.

Now, all of this assumes you have identified the location of the noise correctly. A loose or damaged set of steering head bearings, or even a bad shock, shock mount, wheel bearings, suspension linkage, and a few other items can cause a similar noise.

 

Have you checked your 'sag' on the bike? If, for example, the previous owner weighed a lot more than you, he may have put fork springs with a much higher spring rate. When you're on the bike, the springs are near the top, so when you go over a bump - they 'top out'. Lots of how-to's on checking sag to be found with a google search - if this is what the problem is.

 

TNC

Thanks for your detailed reply!

I don't know the level of oil in the fork, honestly I don't even know how to check (I'm sure I can search for that kind of stuff here on the forum). What you're describing sounds like what's happening. I can feel the fork through the bars hitting its max extension. Another symptom (now that I think of it) is that the fork stays compressed when I do any significant braking, like for a red light. Then when I start off again it will uncompress with the forward momentum unweighting the fork.

I'm about 165 pounds (without gear) so the stock springs *should* be just fine.
Thanks again for your time!

 

Thanks rgmr250!

I'll see if I can dig up any info on the previous rider. I assume the sag is what sort of pre-loading the suspension defaults to when you're not on it. I'll search all that stuff up and make sure it's set up correctly.
Thanks again!
-r

 

TNC nailed it and I agree 100%.

As a prosses of elimination, the easiest and best way to check if your head/stem bearings are loose or part of the cause. Lay your pointer and middle finger across the top steering stem bearing cap and frame head right under the top fork triple clamp. Do this while bike on the ground, standing on the left side, right hand on handlebar pulling front brake lever in locking front wheel. While doing this, start rocking the bike forward and back. Start slow and easy then more up to the point of compressing the forks a little, and skidding the front tire back a little. With your fingers in the correct spot, you will "Feel" any looseness in the stem with your fingers. If they are loose and that is the problem, you'll know in 3 seconds. Just a quick, timeless check of your steering head. But, it sounds to me like what TNC said. But in a few seconds, you can rule out the steering stem. You may also be able to feel exactly what IS happening while doing that check. You can get your eyes and ears up close......

Good luck, and keep us updated with what you find.

 

On what TMC was saying, if it's lost a lot/most of the fork oil, there could be some issues. Generally the oil doesn't just disappear - check the forks to see if there's oil (very light colored, lighter color than engine oil) on the forks - this would indicate that the fork seals are leaking - leaking long enough and a lot of the fork oil could be gone. Again, with what TMC said, loose steering head bearings etc. can cause a clunk.

Re the sag, a brief explanation is: There's 3 'states' of suspension - fully extended (bike on a stand so there's no weight on the suspension), static sag (bike sitting upright on its own weight), and race (or rider) sag - you on the bike, with whatever gear you normally wear sitting or standing as you normally would, off the kick stand. Generally, you measure the rear sag by measuring from the swingarm to a point on the frame - measure the extended - call it A, measure the same two points with the bike on the ground, call this B, you sit/stand on the bike and have a friend measure the same two points, call this C. A-B = static sag. A-C = race sag. Usually static sag is somewhere around 25mm and race sag around 100mm. Very similar for the front forks for measurement. Too much sag and you're likely to bottom out too easily, too little sag, and you'll top out to easily.

 

Thanks for the primer on sag, that makes a lot of sense now. Looks like I will be digging into the fork. Rear suspension is pretty new.

Also, does anyone have any experience with the corrosion in these pics? Can I just scrape that stuff off and clean it up? Should I seal it somehow?

 

I have never seen rust like that on forks. Did this bike sit outside its whole life?

 

No, that's just how things happen on Kauai. Trade off for the whole tropical paradise thing, yeah.