old fouling issue

[ZKDX]

i read threads here everyday about this problem yet i can't seem to pinpoint my problem: 87kdx200, kept fouling plugs...dropped to a 300main (was 320), 2nd position from top on needle, br9es. Better. still fouling plugs ecspecially when riding with son (xr50) i'll putt around or have to keep killing my bike to give him instructions---so i thought i'd try needle position again since i'm fouling at <1/4 throttle, i'm in very top position now and somewhere in the last 2months of trying to get this right, i've also dropped to a 290main. I'm afraid to go any leaner if this doesn't help. Am I barking up wrong tree? sorry to be so long, i've tried to fix this with prob, with what i've been reading here over the last 6months, but to no avail!!!! BTW- pulled kips apart 2wks ago after having just clean them about 3 months prior and they were nasty! (normal? or because of all my fouling) :o :o :o

 

[dirt bike dave]

The main jet primarily effects 1/2 throttle and up. It sounds like you are way too rich on the low speed jetting, espeically if putting the needle clip in the top groove is helping. You can order a leaner needle.

If your carb has an air screw and pilot jet (not all the old ones do), start there. The air screw is a small brass screw, usually on the lower left side of the carb, near the rear. Turning it out will make the bike leaner at less than 1/2 throttle, and makes a big difference below 1/4 throttle. Turn it all the way in first, counting the turns. If you are already more than 2 turns out, try a smaller pilot jet.

Some of the older models have a 'needle jet' that the needle sits in, and this can also be replaced with a leaner one.

Many KDX riders use a hotter BR8ES plug - it is more resistant to foulding than the BR9 series.


Other things to consider: Your oil and ratio. What are you using and what are you mixing it at?

Float bowl level - it is set to the correct height?

Is your silencer clogged?

Is the top end in good shape?

Good luck getting it sorted out!



Some of these maintenance things can make a big difference.

 

[mnnthbx]

If you've noticed my threads, I'm in your same shoes. It is very frustrating that I shell out 4 grand for a new bike that does'nt run right (albeit very fun when it does) . Actually, it runs fairly well, but I have to ride with a back pack full of plugs to have any confidence I'll get home. It is obviously well known that these bikes are set up way too rich, and I am at a loss for why Kawi would not work the problem out...............................

 

[MX175]

Dirt bike dave seems to be on the right track. Tooling around with an XR50 will keep you off of the main jet most of the time. I am almost positive that your carb (probably a Mikuni) does not have an air screw (like the Keihins), so drop the size of your pilot jet. For mid range, you can raise your needle clip (lower the needle), or get a leaner needle or get a leaner needle jet. Are you confused yet? If you get a new needle, you can get it leaner at the bottom or in the middle. Yeah, too many choices.

Most important would be getting a leaner the pilot jet, and then moving the needle lower. Good luck and let us know what happens.

 

[HOTRODKY428]

If you dont run long and hard "like me", throw in a plug for an 86 dodge 318. I cant remember what the specs are, but they are a tick longer, and the electrode is exposed. I put in a used champion from my truck, in 3 years it has never fouled,and my top end has never been apart.

 

[rethnal]

Now there's something for the FAQ's! :)

 

[John Harris]

Be sure your air filter is clean and good. A dirty filter will make you run rich every time. Running rich will foul plugs often, as noted and described above by others.

 

[canyncarvr]

Continuing to drop the main to 'fix' a 1/4 throttle rich situation may well cause a serious problem. You will be effecting the lower throttle ranges, but only on the fringes of where the big change is taking place.

Then, without changing anything, you'll take off on a crisp, cool day on a screaming ride..and stick something.

Main is set by plug reads after WOT plug chop tests. Period. Do what dbd sez..but get your main to something that's correct for WOT operation. That jet series changes by '5s' doesn't it? So...you're down six sizes?

I think you might wanna be rectifying that.

 

[ZKDX]

it changes by 10's started at 320 fouling throughout throttle range...went to 300 (carb parts was out of 310's) still fouling, then went to 290 (so three sizes) but i see that it is my 0 to 1/4 throttle area and that main has nothing to do with it. (now)