Sticking throttle on KDX200

[blackduc98]

Blackduc98
can I fix this without rejetting, will the airscrew adjustment, be an easy fix?"

Air screw mostly helps at idle and just as you come off idle, but it only works when the pilot jet size is close enough. In other words, no it is not a fix for your rich jetting. Why are you reluctant to rejet? It is easier than messing with the floats. Jets are not expensive. When you had your carb apart, did you make note of what jets you have, and the needle position?

please tell me there is an easy fix.

Sure: you can lower the float level. It's an easy fix, though it does have one minor little bitty problem, I believe you are already familiar with it. Perhaps that's why your float level was so out of whack - the previous owner opted for this "quick fix" instead of rejetting it.

 

[rocketman1]

Carb is apart at the moment..Mainjet is a 152, Needle is a R1173, on top clip, with a 40 pilot jet, airscrew is 1 1/3 turns out. I live about 200 feet above sea level.
I would think from what i have read on Just KDX that this bike "should be" now running fairly lean what are your thoughts? bike has a FMF gnarly pipe

 

[blackduc98]

Is there a letter code after R1173? Is yours a KDX 200 or a 220, i.e. what carb do you have? It should be stamped on the side of the carb. You probably mentioned this somewhere, but I looked thru this thread and didn't find that info, sorry.

Standard needle on my 200 (pwk35 carb) is an R1174k if memory serves me right. Optional needles include R1172/3/5/6K, so you could look into alternative needles if that's the throttle range where you're having problems. The difference between those needles is the straight section diameter (larger diameter means leaner needle at low throttle openings). Here is a good reference on KDX needles: http://justkdx.dirtrider.net/jetneedles.html

Another useful reference is James Dean's jetting guide:
http://www.jdjetting.com/xcart/product.php?productid=27&cat=1&page=1

My thoughts are:
1) Call the previous owner and ask him why the float level was so far out of spec. His explanation may save you a lot of investigation.

2) Closely inspect the needle jet and the needle. On some carbs the needle jet can physically wear out, as well as the needle, since they rub against each other all the time. By "wear out" I mean the gap between them becomes larger and out-of-round. This would be bad news since the needle jet on a PWK carb is not replaceable, but you could probably get a machine shop to do it.

3) Probably your carb is not "normal", and the answer to the mystery probably lies with the previous owner. This means that "normal" jetting specs may not apply to you. So stick to fundamental jetting principles and try leaner jets and/or needles.

4) It may be worthwhile to verify float level using the factory-specified method. You'll need to get an adapter which fits into the drain plug (or make your own). You may consider setting float level at the lean end of the factory-specified range.

5) Since you have the carb apart, grab a feeler gauge and direct your attention at the junction between carb body and jet block. The jet block is attached with 2 "secure" allen bolts, and there is a rubber gasket between the jet block and carb body. Very gently see how big of a feeler gauge fits in there, i.e. how well does that gasket seal the gap.

 

[rocketman1]

Bike is a KDX200H 1998 model, carb is a Keihen PWK, needle is a R1173K,
I dont have the owners ph # anymore so I cannot contact him, i have carefully inspected the needle for wear, I cannot see the slightest hint of any wear. I will recheck the float levels and go to the leaner end of the range,
One other thing I should have mentioned is that the carb now loses petrol out the carb overflow hoses when the tap is on and the bike is being shifted about ie onto a trailer, ie motor not going, this has only happened since I redid the float level.I will look at decreasing the fuel level a little and adjusting the airscrew try it out & then if no improvement look at going for a differnt needle and getting a factory float level device, I will keep you posted, thanks very much for your help

 

[craig_enid]

I've had stuck throttle problems in the past, tracked the problem down to a wrong-routed throttle cable. It would stick when riding wide open on whoops, only. Problem solved when I re-routed cable.

 

[blackduc98]

Since your float height is set to factory specs, losing petrol via overflow hose sounds like a worn-out or contaminated/corroded float valve needle and/or seat. Or maybe a defective float. Examine the float needle and seat with a magnifier lens. If you search this forum for posts by canyncarvr you will find one where he describes gently polishing the float valve seat with a thin strip of emory paper wrapped around a Q-tip.

 

[rocketman1]

thanks for this suggestion however, I have reassembled the carb back into the bike, after pushing the float level out to about 17 maybe 17.5mm, (it may have been 15mm) and winding the airscrew out until I got maximum revs at idle. I took it for blast down the street and it appears to be back to its snappy self, I couldn't get it to leak any fuel either, and it is smoking alot less, these two changes have made a huge difference, thanks again for your help, I just hope that 17mm has not made it too lean and recreated the original problem, we are taking it for a good run tomorrow on the track so will keep you posted as to how it goes.

 

[longerdeeper]

Jet Block Seal

Quote "(5) Since you have the carb apart, grab a feeler gauge and direct your attention at the junction between carb body and jet block. The jet block is attached with 2 "secure" allen bolts, and there is a rubber gasket between the jet block and carb body. Very gently see how big of a feeler gauge fits in there, i.e. how well does that gasket seal the gap.")

What can you tell me about this, I have been chasing problems that previous owners of KDX's say have been caused by this seal.
I have tried to buy a replacement but can not find anybody who can give me a part number or name of a supplier.
At the moment I have tried to get a better seal by gooing up the o-ring with 3 bond, but I don't think this is the answer.
Cheers

 

[rocketman1]

Yes it goes alot better on the track, starts first kick again, has good snappy power, though boggs a little coming out of slow tight berms, not smoking too much either I didnt get to check the gap with the feeler gauge will do next time the carb is out. I guess most of this issue was down to the incorrect float level far too excessive 22mm to start with and me a bit on the heavy side maybe 15mm on the other, 17mm has made a big difference, what a learning experience Just KDX has been thanks all for your help. So much knowledge in one site! great!

 

[blackduc98]

jet block seal

I have tried to buy a replacement but can not find anybody who can give me a part number or name of a supplier.
Cheers

I called up Sudco and they say they have it. It costs $5. Sudco has a $25 minimum, so I need to figure out what else I need to fulfill that minimum. If enough people have interest in these seals, I'll buy several and re-send them to individuals.

 

[JacDX200]

I have a 2003 KDX200. Runs great. The throttle has stuck a few times when I had it wide open (smooth straightaway). I can deal with that. Recently tho it has done it in slow sections where the throttle was barely open. Last time it was on a dirt road at about 1/4 throttle and suddenly I was at full throttle. After pulling in the clutch and hitting the kill switch to keep the engine from blowing, I worked the throttle a few times and it came back to idle. FYI this was after a long moderate downhill on a dirt road. Can't figure out how it went from 1/4 to full throttle on its own. I replaced the cable a couple of years ago and it seemed to fix it for about 3 years.

 

[Dirtdame]

I bought my 2003 KDX220 brand new. It ran fine throughout the years until last year when suddenly the throttle stuck. It felt like the throttle closed....but it was not the case for me. A mad stab on the rear brake pedal so that I could reach the clutch and kill button before shooting over the cliff saved me. With the bike safely stopped, I pushed the throttle tube and the throttle crunched shut. I sat there in the middle of the trail and worked it back and forth a few times but then it seemed alright. I cautiously finished my ride, then went home and checked the cable, the throttle housing and the slide. Seemed that my slide looked worn and there was a gouge in the carb body in front of the slide. I shrugged it off as an errant piece of debris getting into my carb. Three rides later, the throttle stuck again. I checked everything. Finally after the throttle stuck five times (and there was always two or three good safe rides between incidents) and I replaced the cable, slide (it seemed to be peeling, so I thought maybe the chrome was coming off and sticking the slide), completely disassembled the carb and had RTVd the filter cage support to the boot (even though there was no evidence of dirt getting in through there when I disassembled the airbox), I replaced the entire carburetor with a brand new one (got a smokin' deal on one from a friend who runs an accessory shop). I decided that it was cheaper and safer than trying to figure out what was going wrong. Now 20 rides later, no sign of a sticking throttle whatsoever. The only thing that I can figure is that after years of riding, the carb body wore enough that if a piece of dirt got in there, the clearance was enough for the debris to get wedged between the slide and the body. :think:

 

[Joburble]

I had a sticking throttle issue once (I managed to lay the bike down). I found the problem to be a kink in the outer that lined up with a kink in the inner at full throttle. Could be worth a look.