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Flanders87

yzf 400 spark plug

10 posts in this topic

Whats the correct spark plug for a '99? Im having a hard time starting the bike and im wondering if maybe its the plug, thanks

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the oem spark plug is -ngk cr9e-

Not according to the Yamaha Owner Service Manual. The Parts book lists both, but the OSM specifies a CR8-E. A CR9-E will foul in all but the hottest weather.

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thanks thats what i put in it. The other day it kicked over 4 times, all but one on the first kick. Today i cant get it to turn over at all, i've been kicking for several hours on and off. ITs been in my basement so it isn't the temperature, any ideas what could be wrong?

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If you did not run it up to operating temperature after starting it, it's quite likely a fouled plug. The 400's and 426's were quite particular about that; they don't like to be started and then shut down cold, especially not repeatedly. If you're going to start it, ride it.

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so if that is the problem, and the only problem if i clean the plug with a wire brush should it fix itself or do i need to buy a new plug?

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Wire brushes are never recommended for that task because they can leave conductive tracks on the insulator. Sandblasting is preferable. Sometimes you can get them clean enough to work just by drying them with carb or contact cleaner, but if such a plug starts the engine, you will definitely want to run the engine for a while to burn the plug clean.

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It's very cheap to replace a spark plug, but in case of emergency or riding for a couple of days : use some sanding paper to clean both of the electrodes of the spark plug (does not apply to iridium plugs) and then hold the plug over flame (preferably gas, like an oven. not wood or similar) for a while.

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