2002 HONDA 400EX, HAVE OWNED FOR 4 YEARS HAS RAN GREAT TILL RECENTLY, TERRIBLE BACKFIRING OUT THE EXHAUST. HAVE PUT NEW GAS IN TANK, NEW PLUG, LOTS OF CARB CLEANER ALL MANIFOLD INTAKE CONNECTIONS ARE TIGHT. NOW I AM ALSO NOT GETTING ANY FIRE FROM THE SPARK PLUG. ARE THE COIL PACK KNOWN TO GO OUT. OR WHAT ELSE MIGHT I TRY. APPRECIATE ANY HELP.

 

It may be the CDI, it may be something as simple as the battery cables not tight on the battery.
You say it ran great until recently. Did it start these symptoms while riding it or after sitting for awhile?

 

CDI, spark plug, spark plug cap, coil, ignition switch, kill switch, decompressor on the cam...
Any of the above ?

----- Gimpster -----

 

mine started running crappy too, just as u described. all it took was a battery change for me! like night and day.

 

mine has started to backfire really bad it used to stop once it got warmed up but now it backfires all the time

 

CAN ANY BODY TELL ME WHICH WAY THE COIL AND PLUG WIRE GO BACK ON. IT WAS LATE AND DID NOT MAKE A NOTE OF THE DIRECTION IT WAS POINTING IN WHEN TAKEN APART, THERE IS ALSO THE WIRE THAT GOES INTO THE HARNESS, I BELIEVE IT GOES ON THE FRONT BOLT. THANK YOU