black sooty plug

5 replies to this topic
  • stroker101

Posted June 12, 2004 - 08:40 AM


hey guy's, hate to trouble y'all w/this small problem. i did a search but did not find my answer. the spark plug in my 03 YZ450F is black and sooty, what do i need to adjust for this condition? it seems the problem just started.
thanks in advance for your help! :thumbsup:

  • John_Lorenz

Posted June 12, 2004 - 09:30 AM



But the question would be where is it rich, Bottom, Mid or top

Best way to to tell is with different reads, an expert would be able to look and see just where it is rich.

What is th bike acting like. is it blubbering in any aspect of the RPM range?
Do you see any black smoke when revving?

What is your current Jetting setup

But black and sooty can be your flavor of gas as well. Low lead cheep gas as opposed to High tech Mobile or 100 octane 76.

Try a different gas brand Highest Octane :thumbsup:

  • OC768

Posted June 12, 2004 - 07:17 PM


could just be that you do alot of low rpm riding and aren't burning it off? is it sort of greasy looking black soot or dry powder? is the very end of the electrode tan only?

...or it could be running very rich :thumbsup:

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  • stroker101

Posted June 13, 2004 - 02:57 AM


i'm pretty sure that the problem is on the low end, just off idle and a little past 1/4 throttle. it devoloped a sputter in that range but would clear up on wider throttle openings.
will turning the airscrew "in" correct this problem?
thanks fella's for your help.
oh yeah...i'm a senior +40 rider and i do ride pretty fast :awww:. thanks again :thumbsup:

  • John_Lorenz

Posted June 13, 2004 - 03:17 AM


You say just recently started to sputter

Would you say this is frm Temp / Weather change time frame?

When was the last time you cleaned the Carb?

I would say that maybe adjusting the air screw may see some changes as well as dropping the needle down one.

But it may be a dirty air jet as well.

If the carb has not been cleaned I would say its ready to be :thumbsup:

  • stroker101

Posted June 13, 2004 - 05:49 AM


i have never cleaned the carb or inspected the jets for foreign materials. :thumbsup:, good idea! i'll tear into the carb on my next day off from work. thanks.

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