spark plug problms

[Aaron Jackson]

I have a 2000 honda 400ex with a stage 2 hot cam in it...im not new to atvs but i have never had a sport atv so i dont know much about them....it is jetted and piped big rev box k and n air filter and it had a champion plug in it RA6HC and it is black and the 400 dosnt run right...it cuts out at high rpms and sputters......i know i need to run a nkg plug but im not sure hot hot of a plug to run.........SOME ONE HELP ME.....

[Kaleigh]

i have some mods and i use DPR8Z

[Kaleigh]

if that doesnt help the topspeed stumble.. you might want to take a look at your airbox and see it its clean.. if the problem has not gone away.. take out your plug and take a look, you should tell if you are running the right air/fuel mixture..white-lean, black/wet-rich, brownish is good.. most likely you are running rich if it stumbles at full speed.. if this is the case.. back down one jet at a time til the problem goes away.. if you get a series of backfire.. after doin this then turn you idle up 1/8 turn til backfiring goes away.

champion atv plugs are junk...i have, nor has anyone else that i know of, had any luck with them in an atv.

the dpr8z would be the plug to run. if switching to that plug doesn't help, the jetting may be a little off

[GPracer2500]

A Champion RA6HC is equivelent to an NGK DPR8EA-9. They are very similar to a DPR8Z. The major difference is the reach. The DPR8Z extends farther into the combustion chamber.

I've used an RA6HC before without any issues.