Sticking throttle

[cadjocky]

The throttle on my 1998 KDX200 likes to stick open at inappropriate times. I've clean and lubed the throttle mechanism, replaced and rerouted the throttle cable. I've checked the slide mechanism for debris, but it still sticks. Anybody have any ideas where I should check next? Could the spring be too weak? Could there be a resonance at certain times that locks the slide in place?

HELP!

 

[Brian]

Clean your air filter and double check for proper seating. It could be letting a grain of sand in, and sticking in the slide, even though you have visually looked over it.

 

[NYkdxer]

How many miles does your bike have on it? Is the slide sloppy in the carb? Maybe it is gettin stuck in there.

Another possibility is that the cable has a broken strand that is catching in the conduit. Does the cable move freely?

 

[cfr1970]

Analyze your problem. Is it happening when there's a lot of sloshing of the gas in the carb going on? Could be you sucked a grain of sand in the bowl (happened to me) Check your needle, is it bent or warped. That will cause sticking (also happened to me as a teenager with a sloppy carb job) Your slide should have a LITTLE play. Check for scoring. Are all of your breather and overflow tubes connected and in good shape? Is your air filter in good shape, clean and seated properly. That should give you some direction.

 

[MX175]

All good suggestions, but also add the possibility of somethig between the handlebar and the inside of the throttle tube that the grip goes on. Or the end of the handlebar hanging out past the throttle tube.


Without more information on the symptoms and severity, it is difficult to diagnose, but I like the bent needle suggestion, and kinks in the cable. Of course check for scoring on the slide. It is always best to isolate things in order to evaluate them. Remove the cable and be sure it is smooth as silk. operate the throttle with the cable removed and it should work like teflon shoes on ice. With the top on the carb, remove the intake boot and operate the slide. Good luck and let us know what happens.

 

[canyncarvr]

Ensure the nylon cable retainer that fits into the needle retainer nut is installed correctly. The tang on the retainer must fit into the slot on the retainer nut.

 

[cadjocky]

Thanks for the resonses. I have checked just about everything you have all sugested. Like I initially said, I have replaced the seemingly good throttle cable with an even smoother one. I rerouted the cable for freer movement. I took off the grip and wire brushed the handebar and lubed it. I made sure the grip was not to close to the handlebar. The grip theory is kinda ruled out because I am forcing the throttle shut by hand as much as possible. The only thing that seems plausible is the dirt getting past the filter and hanging up the slide at random times. I can't say that there is a particular motion that seems to make it stick.

At grip side of the cable, the end piece slips into a pocket with a snap ... I wonder if it is coming out of the snap slightly when I come off the throttle, then not allowing it to come back to idle.

I will check for bent needle and improper filter install tonight. I have taken the carb off and am going to find the problem!

Thanks for the help so far. I'll keep ya posted

 

[cadjocky]

BTW ... it is a 1998 with relatively low hours (< 100 )

 

[23jayhawk]

If you play with the throttle enough, can you make it stick, even without the engine running? If so, disconnect the cable from the slide and try to replicate the problem. You can't prove a negative, but if it sticks when disconnected from the carb then you've found at least part of the problem. (Doesn't mean it's not also sticking in the carb, of course.)

From the 'how could you do something so stupid file' - some time ago I had been moving levers around trying to get the ergos better for standing. Couple days later I'm moving the bike around, and notice the throttle sticking. After taking the carb apart, inspecting cable routing, accusing my son of messing around with the bike, etc, I looked more closely at the grip. I had slid the brake perch to close to the throttle housing. The adjustment screw on the backside of the brake lever was pushing on the inside of the throttle housing dust cover, which was then pinching against the inner flange of the grip. :confused:

 

[kdxmann]

do u run a k&n air filter if u do that could be letting dirt in because it has tiny holes that are larger then that of a foam air filter

 

[cadjocky]

These are the things that I did in an attempt to correct my throttle sticking problem:

1) rerouted my new throttle cable to an even more direct route
2) cleaned the carb completely looking for nicks/bent needle
3) cleaned intake track in front of carb
4) verified the throttle mechanism clean and assembled properly

I hope this does it!

 

[davidg]

I over tightened my throttle tube once and that caused it to stick open. Will the throttle tube snap back on it's own, even with the engine off?

 

[andrew]

Cadjockey, I had similar problems about a year ago that was extensively discussed on this forum. There were a lot of suggestions out there, and quite a few 'it hapens to me as well' comments.
I'll tell you what the final outcome to my problem was. The reeds (boysen RAD valve) were not sitting flat, and somehow that seemed to be creating a lean condition (running on) which felt like the throttle was hanging open. It also got progressively harder to start, even when hot. I suspected crank seals, but they tested OK. As soon as I replaced the reeds, the hard starting AND the 'hanging throttle' problem went away. Those original reeds didn't look too bad at first - maybe a 1mm gap.

Well that was my experience with the problem, hoppefully it may help you.

Cheers,
Andrew

 

[cadjocky]

Andrew ... was the hanging throttle you described a random thing or was it consistant?