A lot of fault spark plugs...

[dimtsam]

Hello everyone
I got a 250 2T 2011 EC. And now my problem is that I have a lot of faulty spark plugs. I found our that when I go downhill, after a while makes the spark plug go off. I thought the problem was the jetting. I put on a smaller jet but nothing happen. Same thing...Then I tried to reduce the gas level in the carb. I adjust the float and reduce it enough. Nothing again...
What else can I do? Maybe a smaller idle jet?

 

[paulos]

Hello everyone
I got a 250 2T 2011 EC. And now my problem is that I have a lot of faulty spark plugs. I found our that when I go downhill, after a while makes the spark plug go off. I thought the problem was the jetting. I put on a smaller jet but nothing happen. Same thing...Then I tried to reduce the gas level in the carb. I adjust the float and reduce it enough. Nothing again...
What else can I do? Maybe a smaller idle jet?

What jetting specs are you running at the moment?

 

[(F5)]

. . . I thought the problem was the jetting. I put on a smaller jet but nothing happen. . .. QUOTE]

What jet? The Mainjet? - that operates when full open throttle position.

. . . . I found our that when I go downhill, after a while makes the spark plug go off.. .

Now we're getting somewhere. Idle jet controls here - and in some cases if the needle is wrong. . . In GG the needles are too thin at closed so you are getting too much wet hard to ignite gas through.

So starting at the start.

Clean filter, replace if grotty. Read up on jetting threads here, get a good needle/idlejet combo. Use decent correct plugs. Replace plug cap if in doubt (I like the blue NGK marine ones).
There is a small chance the coil is a bit crap but do above first. A modified head helps things burn better.

 

[Jakobi]

Don't forget the float height. If the fuel level is too high you'll also get excess flooding forwards into the engine (particularly down hill).

Its about putting all the pieces of the puzzle together. The needle is a big piece of that puzzle, but the rest all has to work with it.

 

[Leo]

....and are you using Grade 8 plugs? Grade 9 plugs are very prone to it on low speeds.

 

[dimtsam]

I' tried both 8's and 9's.Same shit

 

[motopsycho87]

You are most likely running rich in whatever section of the throttle you are using the most causing fouling on the plug. Does it clear up after a good burn through the gears?

Use an iridium plug, I killed plugs every 2 rides, I've had my iridium plug in almost 2 years, it got gammy last week when I rebuild my engine and used 25:1 mineral oil for break in, but runs fine once I thrashed the hell out of it.

BR8EIX is the part number. Please note, KTM 300EXCs use a heat range of '7' to combat this same issue.