Jetting setup for Powerbomb header and FMF Pipe

[K400EX&A250EX]

Does anyone out there have an FMF pipe and Powerbomb header on a 400EX? My brother-in-law has that setup but is currently running with stock jetting. I'm going to help him change out the jets, and was just wondering if any of you out there have that setup and could give me a good idea on the pilot jet and the needle position.

I was thinking about trying a 40 pilot, moving the needle clip down one, and a 155 main. Does that sound reasonable? Any help would be greatly appreciated.

Everything sounds good to me that you listed,,not real sure on the main jet size since I'm using dynojets,,but 2 sizes up from stock should get you around the right spot,,the pilot and needle clip position sound pretty good,,but I'd go ahead and throw in a 42 pilot instead of a 40..my quad liked the 42 pilot more than the 40..:cool:

i run a 42 pilot and a 155 main with needle in stock position. That was with my stock motor and it worked pretty good.
my $.02

[knighttime]

it works for me:D

[K400EX&A250EX]

Thanks for the info. We got the 42 pilot in, needle clip down one, and a 158 main to start. We also installed a Uni Filter and took the airbox lid off.

We didn't have a chance to run it much, and didn't get a chance to actually test it at all on the road (in the interest of maintaining a good relationship with the neighbors!)...but it did at least start right up. If we throttled it up smoothly through the throttle range, it seemed to be smooth and powerful...but if we jumped on the throttle real hard right from the bottom, it bogged pretty bad and even died a couple of times. Any idea what that means? Are we too rich or too lean? Do we just need to adjust the fuel screw or are we going to have to change the pilot jet or needle position again?

Well before ya start tearin into it again,,,is the motor warmed up,,that's a must when dealing with jetting it needs to be at operating temperature. Odds are you can adjust the fuel screw a little to maybe fix it..

[BornOnFire]

I live in AZ and I installed a slip-on WB E-Series on my 400 ex along with air box mods, K&N filter, and grinded the header welds. After much blood, sweat, and tears I finally tuned my carb with the following..

40 Pilot jet
152 Main Jet
Stock needle position
Fuel screw 1-1/2 turns out

Since I live near the same elevation as you, I thought I would share the info...

Good luck

[TRFOXX]

I run a FMF Powercore IV S/A slip on with stock header and I put a 40 Pilot jet with a 152 main jet , Uni air filter and 6 - 1" holes in air box lid and she's running great. Now if I run with the air box lid off im running too lean though, keep checkin your spark plug.

[K400EX&A250EX]

Just a quick note to thank you guys for your replies. We took the bike out today and finally got to test it out. After just a couple of adjustments to the pilot screw, it ran GREAT! My brother-in-law was very happy with the results.

[BornOnFire]

Glad we could all help. Isn't the internet a wonderful thing?