please help before i buy a 4-stroke

[ZKDX]

i'll try to make this short---jetting issues--i'm sure all are tired of hearing from us newbies, but i consider myself pretty mechanically inclined and can fix about anything, but my kdx has been giving me fits for the last 7months..So here's where i'm at: I've got about 7 plugs for this thing that i keep with me, when they foul i take them to work the next day and sandblast them (@$3 ea, i can't afford to buy 4per ride!!!) New airfilter, 30pilot, top clip on needle, and 330main, and new needle seat. Seems to foul within first 1-2min after starting or if i'm riding with son and slowing down,
speeding up, turning off, etc. After the last change (the 30 pilot) i fouled 2 plugs, but i think they were not quite clean (sandblasted) the third one was fresh and seemed to hook up. But i'm not confident the problem is gone. I have the jets to go down to 280, but i don't think it is the main, could it be my recycled plugs, and perhaps now i'm on the mark. I've tried some wot plug chops, but i don't seem to have a good area at the house to get to WOT. Any thoughts would be greatly appreciated, i really like this bike, it's just very frustrating when i can't seem to dial it in! :(

 

[kx200]

330 main thats funny
158 is stock

 

[wibby]

I just looked it up... a stock main jet for that year is a 320 and a pilot jet is 25

But sorry no help out of me


For a WOT plug chop, I just went out and found me a nice quiet road with a nice long straight stretch out in the country. (Well it was quiet before I got there!) :laugh:

 

[Robcolo]

You didn't tell us what plug you are running --very important! If it's fouling when you're putting around --it's obviously not the main jet --most likely the needle. Drop the needle a clip or two. There are also leaner needles available. Try a hotter plug if it still fouls what you are using now. You can tell of the pilot is correct by turning the air bleed screw in, then backing it out slowly. If the rpms increase at about 1 to 1 1/2 turns out, the pilot is pretty close.

 

[Boot]

I'm not sure how repeated sandblasting affects the plugs, but why don't you try going to a hotter plug? If you're running NGKs, this means a lower number, for example going from a BR9ES to a BR8ES. This will tend to burn the deposits off faster.

What about your brand of oil and mix ratio? Are you sure they are what they should be? Is the bike blowing heaps of smoke? If so, maybe on a bike of that vintage you've got a worn crank seal letting gearbox oil into the crankcase.

What you're experiencing is not normal. I have never fouled a plug on my '91 KDX no matter how much I poke around at low revs. Hope you can track down whatever is causing the problem.

 

[G. Gearloose]

1) plug heat range - what they said..

2) I forget

3) can the Mikuni for a PWK, or anything with an air screw to help dial in 0-1/8 throttle.

4) You main sounds fat, perhaps 310 or 320

5) recycled plugs:
you may be compounding the problem. If your bead-blast is also used for metal( al, steel) then you are pounding in metallics into the insulator. about as effective as wire brushing (another no-no).
If you must recycle, get a dedicated plug cleaner with SiC media. Then ensure all the media is out of the plug unless you want lines in your cyllinder.
Then heat the tip with a propane torch to burn residual carbon.
throw those plugs away.

6) choke: (enricher) could be dribbling fuel.

6.5) choke: only use it sparingly, give it stabs of choke to keep it running, don't leave it on until warmed up.

7) float level might be high

8) I doubt your bike specs a resistor plug

9) wibby may be on to something...