'03 400ex fouling plugs...

[btheld]

I have a 2003 400ex I bought last fall. The machine has very few hours on it - completely stock everything (including pipe and air filter). It runs great, except that it fouls plugs when starting it cold. It does this if it is 10 degrees out or if it is 70 degrees.

So far, the best procedure for starting is using the choke, but not touching the throttle until the machine has fired and is running. Then use the throttle to keep it running - once it warms up, starting is much easier.

When it fouls the plug - it's completely black. I'm using the stock NGK plugs...

Any ideas on how to fix this?

[Choppers]

sounds to me like your getting to much gas to it(running rich)

as sson as it fires, shut off the choke. and up your pilot jet froma stock 38 to a 42

[btheld]

Does anyone know the part number of the #42 pilot jet?

magic racing (http://www.magicracing.com/Keihin-Pilot-Jets_p_172-62.html)
or just go to your local dealer ship and ask them for a 42 pilot jet for a 400ex...they should have some in stock

[GPracer2500]

Originally posted by btheld
Does anyone know the part number of the #42 pilot jet?

99103-420-0420

The digits in bold indicate the size. So if you wanted to order a 40 pilot jet from your Honda dealer you'd just replace the 42 with 40, or 45, or whatever size you wanted.

You don't need to get it from Honda though. Anyone who carries Keihin jets should have or be able to get what you need. Stock 400EX carb uses a Series 26 pilot jet although the more common Series 21 will also work. The series refers to the thread location and the length of the jet and is independent from the size (e.g. 38, 40, 42, etc).

[brian-250]

Mine fouls plugs to when i use the choke, if you dont want to rejet, just hit the gas 2 times and start it. Ive done this for about 2 years now and only fouled one plug, that was in the winter when i had no choice.