KDX220 Jetting problems

[Leeb17]

I bought a used '97 KDX220 a few months ago. Here's what it has.

FMF fatty pipe w/turbine core muffler
Boyseen power core w/carbon reeds
1mm over Wiesco piston
Eric Gore porting
145main
42 pilot
needle clip at 2 from top
Using Motul 800T premix @ 40:1

Here's the problem.

When I first bought the bike, it wouldn't idle w/o choke. Idle screw turned all the way in and won't idle. Also, just running it in 1-2nd gear at 1/4 throttle it feels/sounds like its on choke. Very rough sound. Also, there is oil just dripping out of the muffler. At first I thought the power valves were installed wrong, since the previous owner (2nd owner) wasn't to mechanical and had reinstalled the cyl/piston combo. Power valves checked out ok.

After compete carb clean and everything else checking out fine, I dropped the pilot jet to a 40. Not much difference...still no idle. Next I dropped it to a 38. Idles fine..a bit rough, but idles. What I can't figure out is why it still sounds like its on choke at partial throttle openings and why oil continues to drip out of the pipe. I've even taken apart the muffler, completely cleaned it out and repacked it.

The bike runs fine when ridden hard and really screams on top. However the transition from low speed to high speed is not as smooth as other 2strokes I've ridden.

I would appreciate any feedback and possibly solutions to this nagging problem. Someone also told me to check for crankseal leak as I am possibly pulling oil from the crankcase into the cyl ? I have not leak tested it yet, but thought if that was the case, I would be fouling plugs ?

Thanks,

Lee

 

[skipro3]

If you have a crank seal leak you will see a drop in oil level. Assuming you are not using gear oil, I suspect jetting or a float that is sticking or the float valve (is that right?) has a bad seat. Start with the float by checking it's full movement with the bowl off. Should move freely without any resistance. Check the seat by attaching a fuel line to the carb, blow lightly and move the float up with your finger. You should feel resistance to where you can no longer blow air. If you use a clean hose, pull a vacume by sucking lightly and see if it holds. NOt accurate but it will tell you if you got a serious problem. If your bike is more than 3 years old, I would change it out just on GP's. Then check the jetting. Those Boyesen reeds, pipe and air box lid removed allows for the bike to be jetted much leaner. Both FMF and Boyesen recommend a leaner jet with their installation. I have mine as: Main-140 pilot-35 airscrew 1 turn out, needle stock 1173L on the top clip. It works well on either top or second to top without much difference in performance. I am also in Northern California near Placerville about the 2000 ft elevation but jetted for 4-6K ft. This bike starts first kick unless warm, then 2 kicks. Idle is perfect and it has such a small bog when snapping the throttle off idle that it isn't worth the work to figure out. Good luck and if you are near, maybe we can get together to figure this out. I'm always looking for someone to ride with.

 

[Leeb17]

Yes, I have replaced the " float needle" (I've known it as the "needle and the seat") also...even checked the float height....all good. As far as I can tell, I'm not using oil any more than normal. Not sure what normal is, but don't think I'm using. I am using gear oil on the tranny...I thought that's what all two strokes use ?? I use Motul 300t tranny oil. As far as the jetting, I was heading in that direction and was going to put in 35 pilot next. I read where you need to go leaner with this intake/exhaust combo. Didn't think that lean. You would be leaner at your altitude and if jetted for 4-6k than me at about sea level...Gilroy/Hollister. Still, I should be pretty close to that ?

Thanks again for the input. Seems like I only have a few more things to try/check. I probably won't have time to work on it for a few weeks. I'm tending to another bike..TZ250 road racer...crank rebuild.

I haven't been up near Placerville to ride yet. Although a freind wants to get me up to Georgetown area...I think that's somewhat close? I ride at Hollister and Clear Creek mostly. Some day we'll hook up.

Lee

 

[Leeb17]

Oh yea, air filter is uniflow dual stage. Not sure if I like that setup or not. Been using No Toil on last bike and liked it.

Lee

 

[skipro3]

When I said do you use gear oil, I really meant, does your engine gear oil deplete between changes? Is it disapearing? If you need to add additional oil between changes or notice it is low when you change, then it is going somewhere and that is probably due to a crank seal. I've had this on a previous KDX and that was the symtoms: Bad low end, oily exaust, tranny oil disaperaring. Georgetown AKA Rock Creek OHV riding area is one of my favorites and very close for me. Sounds like you know what your'e doing with the carb so just keep going the way you are and it will start working right for you. One thing I am changeing is going to race gas. Not for any performance enhancement but for the consistancy in the fuel and ease of jetting. It seems that every tank from the gas station varies in quality and that is why I was having problems jetting. Using race gas eliminates the variable in fuel as well as avoiding the ethenal / alcohol blends. Did you know that as little as a teaspoon of water in alcohol blended gas will pull all the alcohol out and put it straight to the bottom of the tank. NOw you get a huge slug of alcohol and water, no two stroke oil and can seize the bike. Happened to my riding buddy after dumping in a creek. Avoid alcohol blends like the plague it is. But, I digress....good luck getting the jetting squared away.

 

[canyncarvr]

You might check the needle number. Maybe it's been changed?

What condition is the choke plunger in?

I can't get past the first sentence. With the idle screw all the way in, something is very much wrong if the bike isn't screaming.

You don't mention the air screw. Sorry..but the AS is the brass one, and the idle screw is the black nylon one...right?

Not to be pedantic...but I've been 'round that horn before with a posted 'won't idle' problem. Turned out he thought the idle screw was brass........

 

[Leeb17]

Skipro, Ok, understand. The most miles I've put on it at one time was 45 (yea, I'm weak :) ) and I didn't notice any significant drop in oil level...even after several other rides. I did look at the sight glass and thought the oil looked a bit "milky", like it has water in it. But that was just after shutting the bike off, so it could have been a bit foamy ? But what you describe happening to you, it what's happening with me. I'm going to take closer look at the tranny oil...will drain and look at it for contamination from water etc. I will most likely ride it again next week, so I'll keep an eye on the level. Don't you think it would foul plugs if it was burning tranny oil ? Race gas...hmm. To expensive for me. I run it in my TZ at $6.00gal. I just run 87 oct in the KDX...to low an octane ? Also, possibly your jetting is more finiky since your at higher altitude? Thanks again.

Lee

Canyoncrver. Yes, idle screw is black plastic and air screw is brass. A/S is out per spec..at this moment I'm not sure of spec...1 1/2 out ?

Thanks,

Lee

 

[Humai]

Lee, those bikes really need a leaner number 6 slide or a needle profile change to work properly at low throttle.

I used to have a '98 220 (FMF/TC2) which when jetted stock blubbered down low and spooged. I changed the carb, going to a 35mm with a #6 slide, which calibrated perfectly. The #6 should work OK in the stock 33mm carb as well. BTW, for my bike, the upgrade to the 35mm carb made very little difference to the top end or mid range.

Selection of the right needle profile may obviate the slide change, therefore check this site for jetting and needle specs, as this has been dealt with in the past.

 

[Leeb17]

I'll do a search on this site for that slide/needle info, thanks. The reason I bought this KDX, is, I had a '01 KDX that was completely stock. Ran like a sewing machine...smooth, quiet, no spooge! I am just taken back by the symptoms of this bike, since the changes needed are pretty radical from a stock bike.

Thanks again,

Lee

 

[canyncarvr]

re: too low an octane?

Yes. Spec is 91 in an '00. '97 is still an 'H' model, so would assume it to be the same?

re: slides

Get ahold of ron @ RB designs. He usually has slides on the shelf for cheap (like $45 or so). I tried for months to get a leaner slide (oem is 5mm) from a local shop. I got two large body PWK slides, but never the correct one.

Ron got one to me in two days! He's HERE

re: AS spec

There isn't one. You set it to best 'seat-of-the-pants' response. Best set in (example) 2nd gear, walking speed, under load (slightly uphill) and a quick twist should get you instantaneous reponse. A misadjusted AS will be evidenced by a bog when you wick-it-quick.

For some great jetting input, check the archives for the RB designs carb thread. Pay special attention to JDs input.

Thanks for clearing up the AS/idle part. ;)

 

[Leeb17]

Thanks for the slide info and link to RB website.

Re the octane. Just me being cheap I guess. :) I run 110oct in my roadrace bike, but I'll be darned if I'm going to put $6/gal stuff in my dirt bike. I will try 91 oct next time though to see if any difference.

I'm thinking of going with the #35 pilot and dropping main down to 140. Do you think that is to much ?

Re A/S. Understood. I've always set it by the idle drop method. Turn in until idle speed drops and then back out slightly to get smooth idle. Again, I've been mostly a four stroke guy for many yrs (street, roadrace) and this is really my first 2 stroke dirt bike needing any jetting mods.

I see your CB700sc listed at bottom. Great bike..hydraulic valves, not adjustment, that great torque reaction from the shaft drive. I've always liked those. Re Tech 8's. Not sure what that means, but have you tried Fox's new Forma Pro? Very nice !

Lee

 

[Leeb17]

I'm having problems doing a search. Up above these posts, I click on Search. I put in "JD Designs" and it says "not enough characters". Can someone help me with searching at this site. I'm still new here...sob, sob.

Lee

 

[Leeb17]

Oops, I mean RD designs.

 

[canyncarvr]

1. The search function is experiencing a SARS attack. It's barely breathing. You can search by username, but word delimiters haven't been working.

2. Don't know if it's RB Designs you're looking for, or threads referencing the company. When I said, Ron got one to me in two days! He's HERE above, the <HERE> is a link that you can click on to go to his site. If it's threads you're searching for, goto #1 ;)

3. And I think you mean RB designs? His name is ron black, btw. 'JD' is james dean, a jetting gehru/mechanical engineer that knows stuff.

4. AS set using 'lean roll' method. That's a 4-str 'tool' for sure. Not applicable to 2-str.

5. I'd had a hankerin' for a 700SC since, oh......about '86 (second year they were made). Having ridden r5's and rd's for decades, I finally decided it was time to 'graduate' to a UJM (universal japanese m'cycle..or 4cyl transverse mounted in-line bike). I DO like it quite a bit. It's a noisey SOB, though. The little 1/4 fairing dumps turbulent air from the square headlight right on my head. Raise up on the pegs just 10", and the ensuing quiet is wonderful! One of the reasons I went 4-str is to get more miles on a tank. Ha! The 700SC tank is of course, PUNY! When it hits its sweet spot (about 9500rpm), it's FUN! And a set of battle ax tires can make your head devoid of all fluids on corners! YeeHAW!!!

6. The tech-8 remark is kind of an inside joke, I guess.

7. Here's a link to the archived thread I was talking about...with JD's valuable input:

http://www.dirtrider.net/forums3/showthread.php?s=&threadid=19686


This is in 'archived posts'. If you go to the forum front page (that lists all the forums) it's next to the last board listed. It comes up with 'no new topics added in the last 30 days', but change the display to 'since the beginning' and you can see all sorts of good stuff.

Have fun!

 

[Leeb17]

Thanks. I'll have to re read that again...lots of info. If I have to go through all that to get my bike from puking oil and running good, I'm selling it and going WR250F ! I might still do that anyway.

Lee

 

[canyncarvr]

Re: too much stuff

A day without learning is a like a day without.......well....hemorrhoids maybe?;)

Take a look at the coil rewind post on the archives board. Read techman's posts. Cripes! There are a lot of people out there that know a lot of stuff!!

......I like the square wire idea. Didn't see that developed, though.

Have fun!! Don't give up on it yet!!