KDXRIDER.NET

Hi all. Just bought a 1994 kdx 250. Got the fork seals changed which you guys helped me with and went for a blast for about an hour.

Towards the end of the trip i got stuck down a bottle neck road jump off to move the bike and it revved really hi all on its own, i hit the kill switch and it died. Started her back up and off i go again for 5 mins home.

Since then i have cleaned the filter. Today thought i would give her a blast, started it up and started revving high again, killed it started it and done this for 10 mins. Didnt always do it when it was ticking over but as soon as i touched the throttle revs high and i kill it. After 10 mins it stopped doing it and i managed to go around the block 4 or 5 times with no issues.

Now obv i have been doing some research and im worried its an air issue, possibly the crank seals. There is a small amount of oil leaking for the manifold, silencer join. Black black oil but i know this can be normal. One thing i did notice today is in the gear oil check glass when the engine is running i can see the oil circulating. Is this normal??

So thats everything i know, at the moment im feeling pissed as its a clean bike and was sold as excellent condition so i paid top price and may be paying a little visit to the guy.

Any ideas guys?? im really stuck. Just an update, 2 hours after i posted, i thought i would start her up again take it round the block then back into the garage, started fine, got 5 metres then it died and wont re start anymore. So im guessing that spark plug and nothing else more serious?

out
of
gas




on my KDX 200 I can always tell when its about time to switch over to reserve because the bike will rev out like that, pull real strong and then fall flat

I would top her off and see what happened



about going back the the seller
I don't know about finland but here in the US there is no implied warranty and unless you can prove fraud all sales are "as is"

Clean the carburetor?

vacuum or pressure test?

Thanks for the response. She has plenty of gas, i filled her up when i got it and have around half a tank left so pretty sure its not that. So are we saying its not crank seal related?? im still unsure about the tranny oil circulating around in the check glass? or am i being a tit :)

Well i think i will put a new spark plug in it ( just realised u have to take fuel tank off to do this, great design idea there!) Clean out the bottom of the carb. I have just cleaned air filter so thats done.

Set the float height while you are in there. An incorrect float height can cause the symptoms you are describing.

I've been there with the float height. If it is too low, it won't get enough gas at higher or maintained speeds. The result is overheating and surging but won't keep a steady rev...

It sounds like your slide is just sticking open, may be a dirty throttle cable. The only way it can be revving is if there is a big enough vacuum leak. Likely not crank seals if it revs that fast.

Gotanubike wrote:I've been there with the float height. If it is too low, it won't get enough gas at higher or maintained speeds. The result is overheating and surging but won't keep a steady rev...

It sounds like your slide is just sticking open, may be a dirty throttle cable. The only way it can be revving is if there is a big enough vacuum leak. Likely not crank seals if it revs that fast.

I had a bike a low float height, that rode great, kept a steady rev, but occasionally (most often after start) would have a sudden lean take-off.

Check your throttle cable and slide. Have seen similar issue where the culprit was grime that had found it's way in through the throttle cable boot at the top of the carb and built up on the back of the slide where the cable attaches. Every now and then some of the crap would stick the slide open and cause an over rev. Would be worth pulling the carb and giving it a good cleaning (easy job that takes all of 30 minutes). Make sure your cables are properly lubed, adjusted, and routed. On my own bike I had the same symptoms, which caused me to cartwheel the bike on a climb. In that case I had recently changed bars, and in my hurry to go ride I had placed the brake master and the kill switch in the wrong positions. It caused the rubber throttle shroud to drag on the grip, and every so often wouldn't allow the throttle to snap back closed. The bent frame as a result of the crash is what prompted me to build my hybrid

I'm going with dirt/grime on the slide. I had mine take off on me while riding a whooped out section of trail. Ended up that a (TINY, TINY) bit of water got in the slide and kept it from going back down when opened full throttle. It just hung there (imagine that ). Clean that carb up, make sure the cable and boot are clean also.

6 Riders wrote:I'm going with dirt/grime on the slide. I had mine take off on me while riding a whooped out section of trail. Ended up that a (TINY, TINY) bit of water got in the slide and kept it from going back down when opened full throttle. It just hung there (imagine that ). Clean that carb up, make sure the cable and boot are clean also.

I temporarily dislocated my shoulder last summer after that happened to me! Except we were at some sand pits and there were huge puddles that we were going through at full speed. My throttle stuck at WOT and I just bailed off...didn't even think to pull the clutch

Ok thanks guys. I will give the carb a clean and look into getting to the slide, dont know where this is. Its pretty much my 1st bike so im a beginner
Thanks again appreciate it.

Also one more thing, how do u know where to set the air screw?? i started to adjust it as it wasnt ticking over all the time, didnt seem to make any difference and now not sure where it should be set.

I think it should be between 1.5 and 2.5 turns out
the fact that turning it doesn't affect the way the bike runs is telling us the carb is not jetted right

I wonder if your reed are good ?

Ok well i check it out over the weekend and have a look at the carb. With relation to jetting and how the bike was running, it was running fine apart from some white smoke and a bit of spuge from the silencer join.