Accessing jet?

[JOEX]

I bought a used '01 400ex awhile back. It came with a K&N filter with outer-wears and a WB E-Series slip-on. I would like to find out if the jet has been changed, it seems to run fine but I don't have anything to compare it to. After reading some other posts about jetting i'm a little concerned about running lean. I also ride at about the 3000 ft where I understand is the borderline for a jet change.

Do I access it from the top or bottom?

Does the carb need to be removed? If so, what parts need to be removed to get to the carb?

I will be getting a service manual soon where i'm sure this stuff is coverd. I'm just being a little impatient right now. lol..

Thanks, Joe

[mikeboone]

Yes, you need to remove the carb. Start by turning off the gas. Loosen the screw at front and back of carb. Remove The black gas hose from tank to carb. There are 4 small screws on bottom of carb. Take these off and there are your main jet and pilot jet. The pilot jet affects mostly idle and main from 3/4 throttle to full throttle. The main jet sticks up farther and screws in the holder; and pilot is in a hole. Before you remove be sure you have a jet to replce it with. It really is no use to know how to remove if you dont have an idea what to put back. The stock main is a #138 and stock pilot is #38. If you go up a few sizes on each; you should be ok. When you put back in; DO NOT turn hard. Just snug it up; they will strip easily. Replace the cover and 4 screws and hook back up. Turn gas on and try it out--search some older posts to help you decide if it is running rich or lean--hope this helps

[knighttime]

You do NOT have to remove the carb to replace you main jet. U will see a chamber cap at the very bottom of your carb. Remove this cap with a 17mm socket. From there you will be able to remove the main jet with a 6mm socket. The jet size will be on the side of the jet. When u re-install the jet dont tighten too hard or you will strip the brass threads, but be sure to snug it tight enough to ensure it wont vibrate itself loose.

[JOEX]

If I take the carb off and open it up will I be able to tell if its the stock jet?

If it is an aftermarket jet how are they marked so I know what size to go to once I figure out if its running rich or lean?

Thanks, Joe

[knighttime]

You dont have to remove the carb. You only have to unscrew the chamber cap (its the bottom most portion of the carb). When you remove the main jet, it will have the jet size stamped on the jet.

But, if by running fine you arent fouling plugs, then you have nothing to worry about. Wait till u get the manual before doing anything then.

[mikeboone]

I just told him to remove the carb and replace the pilot also. It will start much easier if he goes to a #42 or #45. Thanks for help-Knightime

[stevengates45]

i wouldnt worry about ur jet. to see if ur runnin lean, just check ur spark plug. just my .2 cents thouh