Main Cause Of fouling Plugs??

[ShiftFMX]

What is it? I use NGK BR9ES's. I run Maxima 32:1 with 110 octane

[ZRider400]

weak spark, ****ty jetting (too rich) , not riding it the way its supposed to..example..not revving it enough, and just putting around

I would switch to the B8ES, ive been running that in all of my 250R's.

my old 250r did hav eplug fouling problems which was from weak spark, but my new build has no problems and i run B8es.

[ShiftFMX]

Originally posted by ZRider400
I would switch to the B8ES, ive been running that in all of my 250R's.

my old 250r did hav eplug fouling problems which was from weak spark, but my new build has no problems and i run B8es.

Is it the BR8ES?? If so, I picked up one of those this morning, seemed to run fine, I'll pull it out tomorrow and see what color it is, I may need to mess with the jetting jusssst a hair. She runs like a champ, but its a ***** trying to start a bike with a fouled plug!

yeah i think my R is running too rich too, and i let my GF drive it and she didnt ride it liek it was supposed to be ran and fouled a plug....i am also a lil scard to change the jetting in fear of burnning up a piston or somethin

[wilkin250r]

Fouling plugs can be caused by many reasons. The most common is probably rich jetting.

The first thing you need to do is figure out WHERE you might be rich. It's very possible to be rich at idle, but lean at wide-open-throttle. You have different components that control the jetting for idle, mid-throttle, and wide-open throttle.

Do a search in the powertrain forum for "plug chop". Somewhere you will see a procedure for running your engine and checking your jetting by reading your spark plug. You'll want to do a few, at idle, mid-throttle, and WOT.

Going to the BR8ES will also help. It's a hotter plug, so it will burn off deposits a little better.

[250RGUY]

BR8EG is hotter burning race plug my friends run them in dirt bikes.

[GPracer2500]

If it turns out not to be a jetting issue, the second thing I would investigate is a bad crank seals. A bad clutch side crank seal can foul plugs from gear oil. A bad flywheel side crank seal can make them very, very hard to start. Just a though.