please help

[12345mrjeff]

i was wanting to know i have a 2001 400ex it has a aftermarket pipe but i dont know if it has ever been rejetted is there any way i can find this out and what do i go with if it is not in for months i well be doing a 440 big bore kit so if anybody knows please help thanks alot

[JOHNDOE83]

wait on jetting till you get your big bore kit, jet sizes will need to be alot bigger to accomodate the big bore.

stock jetting is a 148 main jet, mine has a 220 main jet.

yours will be different, I suggest getting your big bore kit and also getting jet sizes from 148 up to 190 along with a 42 pilot jet.

id get the jets in incriments of 5, to keep cost down.

www.jetsrus.com check their FAQ's section on how to rejet.

[12345mrjeff]

alright man thanks for the help i well wait intill i get the kit in before do anything

[a4guy]

With your current setup it will back fire on decel while you are running it if it not jetted correctly. If it doesn't then it might fine. It is not wise to run a machine while it is not properly jetted. By adding an aftermarket slip on you will need to rejet and if you are planning on riding for a while before you to your bore I would go ahead and get a jet kit. I got the fmf jet kit for around $30.