Spark Plug Breakdown

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Mar 3, 2001
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#1
Left the bike on tickover for about a minute and it stopped.Removed the spark plug which was black and wet and cleaned it and refitted.The bike started first kick and run for about another 30 seconds then stopped,so i fitted a new plug and the bike now runs fine.The original plug was only about a month old and this is the second time this has happend.The plugs are the correct standard items and the jetting is all standard to the best of my knowledge but the air box lid/snorkel has been removed.Any help please,Thanx in advance.
KDX 200 H2 1996
 
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#2
Once a plug is wet fouled it may never recover properly so change it. Use the recommended heat range. So an NGK rep told me...Hmm. No I do believe him.

New bikes are usually set up too rich as it is the safe option. If you are using a decent oil at the ratio recommended on the bottle then it will not be the problem, ever.

Why leave the bike to idle for minutes at a time? This is bound to foul the plug eventually. Start playing around with the jetting particularly at low throttle positions (Pilot etc). Use the recommendations from the website & various threads as a starting point.
 
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#3
Cheers David,I run the bike on 40:1 mix at the moment but I am gonna change that to 50:1 as recomended on the oil bottle,Thanx for your time and tips Cheers.Chippy:)
 

MADisher

Grand Data Poohbah
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#4
Chippy if you change from 40:1 to 50:1 you'll end up richer (less oil = more gas) which is fouling your plug not the oil.

Search for other threads on the topic.
 

canyncarvr

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#5
repeat?

chippy...You're clear on the 'rich...safe option' part having NOTHING to do with premix ratio, right?

Regardless of what ratio you're using, if your bike is 'too rich' (and it is if it's as jetted from the factory), it's the jetting (pilot jet, main jet, needle clip position, the needle itself, air screw and possibly the slide/throttle valve) that need to be changed/adjusted.

..which of course all changes with humidity, temperature, elevation and barometric pressure.

Sounds like a lot of fun, huh??? Of course it is!!!

:D
 
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#6
Yeah that’s what I was saying, thanks for clarifying. If the oil is somewhere in the right ballpark it is irrelevant to your problem, just be aware that changing the oil ratio changes the petrol content of the mixture you pour into the tank.

The engine will suck the same amount of gas into the cylinder through a given jet size irrespective of what it’s sucking. (yeah yeah if the viscosity is the same).

You need to alter the petrol to air mixture which is set up on the rich side from the factory.