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fouling plugs

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Oct 14, 2003
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#1
I own a '86 model KDX 200C, and recently the bike has been going through 1 plug every hour of riding!!
I have a mx style track and after roughly an hour of riding there is suddenly no throttle response and the bike dies. I run NGK BR9EV plugs (which is correct) and every time I remove the plug it is oiled up.

as much information and help as possible would be much appreciated.

Jade Heys

ps I am new so please be patient with my forum skills!!
 
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#2
First thing I would check is see how dirty the air filter is. If it's dirty that could be your problem. :thumb:
 

RJ-KDX

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#3
I would highly suggest you go to the Just KDX website and read about jetting. There is a thread at the top of the main page. There are too many factors to cover here, also you can do a search on jetting, I hope you're sitting down.

Good luck..... :yeehaw:
 
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#4
The 'and recently...' part implies that this is something new?

Look for leakdown (pressure test) information on this forum...one post complete with pictures and links to complete instructions for building a tester and doing the test was quite recent.

And here 'ya go...... a search on this forum for 'pressure' gets you this (from 10-9):

CLICKY CLICKY
 
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m1a

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Oct 20, 2002
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#5
Clean air filter, br7es or br8es, mix ratio 48:1 synthetic oil, mine has worked great in this config for years but would not run at 32:1 it just fouled out all the time only two stroke I've owned that acts this way but it works now and not problems for 2 years all my other bikes ran 32:1 but my kdx won't, I took it back to the dealer and had him tune the carb just a bit but it still had to run 48:1 to keep from fouling out.
 
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#6
Sorry, but 32:1 is leaner than 48:1. :(

If you're fouling plugs (mechanical problems notwithstanding), you have a improperly jetted carb.


Well...or you ride with the choke (enrichment circuit) 'on' all the time? ;)
 

RJ-KDX

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#7
Ooohhhh boy. Now let's see where did I put those can o' worms? Hhhhmmm..... :laugh:
 
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#9
I avoided the jetting issue on purpose. The post indicates this is something new. I assume that to mean the bike has been ridden enough to get an idea of how it works...and if jetting was off enough to foul plugs, it would have always been doin' it.

Right?

So...something else has happened. Like a crank seal.... :(

Thus the leakdown test input.

Would be nice if it was a jetting issue. That would be much easier to resolve.

Co$t less, too!!
 
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#10
sorry guys i forgot to mention....

I haven't had the bike for that long and my dad is a qualified motorcycle mechanic so he does the work for me. My riding spot isn't high up or anything so altitude isn't an issue realy. Ive had the bike for around 2 months and it only started fouling about 2 weeks ago. Dad hasn't worked with KDXs before though so he asked me to join the forum... It sounds like you guys think it has somethin to do with the air filter or jetting thanks heaps!

forums work wonders!!...

hope the extra info helps....

thanks heaps for the replies
 
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#11
Another go.....

If you have had the bike that short a time, you haven't had the time to get a feel for what's 'normal'.

Start with the basics if you haven't already (surely you have, right?). Any jetting should be done with a clean air filter, otherwise you are wasting your time.

Plug fouling in a kdx that has not been rejetted is common.

Go to an '8' plug as jason said. An -evx is nice, but not a requirement. You can use a less expensive plug to set the bike up, then if you wish you can change to the rare-metal plug for reliability after the jetting is sorted out.

...and you didn't list your current jet-set. You can't get any reasonable advice on which direction to go if you don't say where you are!

I read somewhere,
as much information and help as possible would be much appreciated.
;)
 
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#13
dad went and got me an a better plug and he asked what was wrong with the bike. Dad told him and the problem was that we had used premium fuel and had mixed it too rich because we had rebored it. Ill get the current jetting settings tommorow though.

roosta