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SoUpX
12-28-2004, 07:27 AM
I may sound like an idiot but, Since the weather has gotten colder i've had two spark plugs that fouled up. But I bought a champion plug from wal-mart, dont know which one it just looked similar to the stock one but it is shorter) This doesnt foul up, but it backfires after I let off of WOT in 5th... what going on ?? thanks

mmartin
12-28-2004, 08:33 AM
you have the wrong plug in

Just because it looks that same that does not mean that it is. Different plugs have different heat ranges will make the bike fire hotter or colder.

Rico
12-28-2004, 08:38 AM
get the correct plug and leave the dam choke alone when starting it.

underpowered
12-28-2004, 08:50 AM
the problem is you are running a champion plug. I have nothing against champion but i cannot get them tp last in any small engine, whether it is a lawnmower or a quad. get the correct plug, preferably an NGK from the local shop.

khen
12-28-2004, 09:13 AM
I ran one of those Champion 400EX plugs from Walmart. It seemed to run quite a bit hotter than the NGK plug which may be why yours didn't foul and is backfiring.

Lou400ex
12-30-2004, 09:03 AM
400ex uses DPR8Z (NGK) OR X24GPR-U (DENSO)
If you are running in high speed alot use (DPR9Z(NGK) OR X27GPR-U (DENSO).
HOPE THIS HELPS.
Lou

SoUpX
01-02-2005, 08:54 PM
yeah i know that the champ plug is the wrong plug.. .Duh, but when i use the DPR9Z or DPR8Z they foul, the Champion doesnt foul....... It's probably just because the choke, but i just wanted another opinion...... does any body elses plug foul ( I mean I started it and rode for about an hour (twice) , came inside and about 2 hours l8r tried starting it and had to push it in the garage to check the plug that was fouled (this is the second plug 1 DPR9Z and one DPR8Z) So I put the champ back in so i could ride.. Why does it foul when i use the choke, It was like 5-18 degrees that day...

trick 400ex
01-05-2005, 05:25 PM
my 400ex has the same problem and i have too put a new plug in about evry two months,and my quad stays in a heated garage and still has a hard time starting up