which sparkplug for 400ex

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Feb 23, 2008 | 12:38 PM

treekiller

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which sparkplug for 400ex

i have a 07 trx 400ex.when we ride, we go fast and ride hard for extended periods of time. about to do a little bit of racing. is the factory plug o.k.,or should i "upgrade"? keep in mind we never put around.

Feb 23, 2008 | 01:11 PM

hondabuster

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which sparkplug for 400ex

If the motor is jetted correctly, the stock plug is fine.

Feb 23, 2008 | 01:20 PM

treekiller

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which sparkplug for 400ex

the only modifications are a muzzy slip on exhaust and k@n filter w/ air box lid still on.never messed w/jetting

Feb 23, 2008 | 03:14 PM

hondabuster

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which sparkplug for 400ex

Both of the things you did, changed the jetting, maybe not much, but whenever you do things to allow more air in and out, you need an increase in fuel too.