Um acually a 4-banger can foul a plug...Sometimes if you over fill the oil, or if your motor needs new rings it will not move the oil back down the jug and try to burn it. Just liek one of my 200x's (needs a top end) it will foul plugs all day long with somebody other than me driving it because they dont know how to drive it liek that.

 

well guys the plug was oil soked. so i bought a new plug and it started right up in one push of a button. I think my oil was to full . but when the guy sold me the quad he told he is fouled sometimes and he has a running rich so he didnt burn up the motor.

 

400ex's are jetted lean from the factory so they are hard to start. i would put a 42 pilot jet in and it will start better. also, when starting it don't keep giving it gas. you may want to pump the throttle 3 or 4 times before you hit the start button. then hit the start button without hitting the gas.

 

my 83 and 84 big reds had their origional plugs untill '97, when i decided to change plugs for the heck of it. that was a mistake. i couldn't get more then 3 days of ridiong before the plug would crack, foul, or make it hard to start. after going though a lot of NGK plugs, i switched to champion. no problems since. still have those champions in there. also, my arctic cat 500 fouled it's plug in the first 200 miles. my dealer gave me a new plug, and that one has held up and now has 2000 miles on it.