ATC 350x 400ex carb Jetting.

[sunfire704]

I'm putting a 400ex carb on my 350x. What jetting do people normally run?
My motor isn't going to be stock.
It will have porting,DG krome header and suppertrapp silencer.
Megacycle regrind cam
5 angle valve job.
Uni filter and ported airbox lid.
Anyone got any suggestions where to start with jetting?
Stock 400ex carb jets are 148/38

[350for350]

I'm no jetting expert so I'm just grabbing numbers out of thin air, but here's my opinion. I know the stock 350 main is 138 and it seems like the pilot is 35(?). If you just had the airbox and exhaust mods, I'd suggest seeing how close the stock 400 jets are. With the cam and valve porting, I'd try around a 160 on the main and maybe 40 or 42 on the pilot.

[RIDE-RED 250r]

I have seen most guys that run a 400ex carb find that stock 400ex jetting is pretty much spot on. I have been following this topic for awhile as I have a 400ex carb an want to put it on the wife's 350x. I just need a couple of the choke parts...

[userj8670]

I have a supertrapp (not stock) header & silencer, 400ex carb and UNI filter. Stock jetting on the 400ex carb was lean on the pilot. I believe I'm a 150 main and a 45 pilot. It's not perfect but close. ..