400ex jetting

[RideRed09]

i just bought a 2006 trx400ex and i bought a White Bros E-2 series S/O. the pipe came with a 155 jet but no needle and the stock needle ended up being nonadjustable with only one setting. so i put that 155 in and left the stock needle. should i put in a bigger jet and a adjustable needle? Please help, thanks.

[HawkGT]

Yeah, for 05' & 06' the carb is slightly different and the needle is non-adjustable. You could shim the needle with washers or I'm 99% sure the 99'-04' adjustable needle will work. With just a pipe though, you're probably just fine with the stock needle postion.

[RideRed09]

is that 155 jet okay or should it be bigger?

[HawkGT]

is that 155 jet okay or should it be bigger?

I'd guess that it's close, but really you should adjust your jetting based on how the quad's carburation behaves--not because of what Joe Blow Internet told you (me in this case).

How does the quad run at wide open throttle?? That will be your best guide as to what main jet is ideal for YOUR quad in YOUR environment.

One easy way to richen or lean the jetting without actually changing any jets is to remove the airbox lid. Lid off = more air in = leans out the jetting. Lid on = less air in = richens up the jetting (compared to lid off). Use the lid as a tuning tool. Take the lid off: If it runs better then you know your current jetting is too rich for running with the lid on. If it runs a lot worse than you could be too lean with the lid on. Get the idea?

Until you've got the experience to feel and hear an engine and be able to make an accurate assesment of what the carb is doing, jetting is mostly a trial-and-error process. Even with tons of experience it often comes down to trial-and-error for that last little bit of fine tuning. Move the jetting in one direction and see if it gets better or worse and on and on...

[RideRed09]

im goin to try that thanks.