fouled spark plugs

[jerryme72]

hi,i got a 91 kdx 250 a couple months ago.it was in pieces as the previous owner wanted to paint the frame,anyway.i got it all back together and it ran great after taking off the airbox lid (it was starving for air).than the bike started to foul plugs after two or three rides-ngk br9es.i am running the bike @50:1 with 10w30 in case.so i went and got a couple different plugs br8/br7'the 8's lasted longer but the 7's the longest.i didnt want to go hotter after the 7's kept fouling.before i rip the bike apart to check crank seals or to see if anything else is the culprit---are there any suggestions for the cause of this plug foul problem like electronic or my fuel mix or anything at all..any help will be apprieciated.thanx jerryme also when the new plug is installed the bike runs xxx-cellent...

 

[Rhodester]

What's the plug look like when it fouls? Many times fouling occurs from a rich mixture (fuel/air).

 

[jerryme72]

my fuel mix is 50:1 and i have the air screw out 1 1/2 turns.. when the plug fouls it is usally oil fouled..all black and full of oil..i have used a 50:1 fuel mix in every bike i have owned with never any problems..it is kinda like this bike is full of oil in the top end........

 

[G. Gearloose]

drop the needle.

 

[John Cena]

like G. Gearloose said put the carb needle clip up 1 or two notches, try turning out the aircrew a half turn. :nod:

Your probably to rich on the main carb jet or the Pilot jet, maybe both.

 

[jerryme72]

i dropped the needle(put the clip up 2 notches)and the bike came alive...i mean more top end and best of all,after riding all day not one plug fouled out...thanks for the fix

 

[Rhodester]

Now keep going and get all the circuits jetted just right. You'll be glad you did. BTW, I'd be hesitant to jet via the spark plug temperature range.

 

[TriniG]

10w30w? Watch that oil

Hey, I was just looking at your thread and you said you were mixing a 10w30 oil at 50:1 ? is that a 4 stoke oil?

What oil are you really using? You should have a good brand 2 stroke oil or racing 2 stroke. I'm using a synthetic oil made by Belray and mixing 40:1 which gives me a leaner gas/air mix. Works great on both my '98 220 and my '93 200.

 

[jerryme72]

I am using 10w30 in the crankcase(transmission) / I use 2 stroke oil with gasoline at a ratio of 50:1