42 pilot jet

[oldmanona400]

I would like to replace my stock pilot jet with a 42, but I don't konw what size carb is on my 03 400ex. Can someone help?

[Mobile Dyno]

Is it a stock Carb? Do you have any motor work done. I just drilled my pilot out to the next size and it starts nice with the 440 at 312 ft(altitude). Do you know what your 's is?

[oldmanona400]

Bone stock. I'd like to get the most power from it without using an aftermarket exaust. My plan is to put a K&N air filter and Power lid on it, and remove the choke.
I also plan to mix 50/50 race fuel and premium.

[Rico]

Your stock pilot jet is 38. You should go up to a 40 or 42 and it is not going to up your HP, only make starting easier and helping it idle better.

YOu need to change out your main if you add the K&N kit you mentioned. YOur also going to be pissing away money running race gas in a stock motor...:cool:

[oldmanona400]

easier starting is the reason I wanted the 42. I don't want to buy a complete kit. Dennis kirk sells the individual pilot jets, but I don't know if it's a 21 or 22 series. The main jet kit comes with the K&N power lid, but I'm not sure if it comes with a pilot jet also.

[Mobile Dyno]

If you are taking the choke off then I would say try a 42 but I think the 40 is where you want to be. I agree with Rico on the race fuel. Waste of money on stock motor.

[oldmanona400]

Thanks for the info on the fuel. Do you know which series pilot jet it uses?

[cals400ex]

they use keihin 21 series pilot jets. this 42 pilot jet will be a little longer than the stock pilot jet, however this is normal.

[oldmanona400]

Thanks to everyone who replied. Ride hard, ride safe, and be courteous to the environment.