400ex carb on 350x questions/help

[i58829]

Can someone please tell me the advatages here i will have a mostly stock motor w/K&N filter, modified airbox, and DG header/silencer. Is the 400ex carb easy to tune once its on the machine and do i need any major mods to get all to work, also how do i go about jetting it since its a smaller engine? What are you guys running? Thanks for the help, TC...

[Dirtcrasher]

I believe it is a bolt on. It must have a bit upsized jetting which I would imagine are closer to what a 350X with an exhaust and an open air box lid would work best with. They may have a better starting circuit to help them start easier, but I haven't confirmed that. And they have an accelerator pump built into them.

I'm sure they are just as easy to dial in as the 350X stock carb. I would definately only run either a Keihen 10 86 350X carb or a 400EX carb... and not the 85 model which I think is an 05Keihin....

I let ya know when I put the 450R exhaust and 400EX carb on the 350X I'm working on for my buddy...

[Gunnar]

Whats wrong with an 85 350x carb??

[Dirtcrasher]

Whats wrong with an 85 350x carb??

It just doesn't have the updated starter jet setup that the 86 350X carbs have.

And, the 400EX carbs out there are 10 years newer and just as cheap and have the accelerator pump.

[i58829]

I picked up a '06 400ex carb (<$45 shipped) thinking i'd get better throttle response and maybe easier starts, and it wasn't a ton of money but i'm curious how much work i'd be getting into. I also bought the newest one i could find hoping that it wont have any issues and need gone over before installing...

[350Kris]

Can anyone confirm for sure -- is a 400EX carb a direct bolt-on to a 350X?

[Dirtcrasher]

Just for you guys I left my cozy warm chair and entered the 10 degree barn...

The 350X carb intake is 40mm, back is 54mm and it's about 4.250 long.

The 400EX carb intake is 44mm, back is 58mm and it's about 4.8125 long.

Thats a 4mm difference that your boots will have to expand or just under 3/16th of an inch.

And about 9/16th of an inch longer the boots would have to deal with.

So, NO - it isn't a direct fit but it may squeeze in there no problem. I certainly plan on fitting the one I have onto a 350X.

[SWIGIN]

i take it those measurements are out side diameter

[Dirtcrasher]

Yep, those were the quick OD's on the necks of the carbs I took while trying not to freeze, LOL!!

I figured everyone is more concerned with the "fit" rather than the inner bore. I'll measure them too, this weekend when it reaches 50 degrees....

[i58829]

I am waiting for a carb to arrive, i bought an 06 400ex carb, and i still have my 350 assembled but i have a bunch of parts here and on the way, it's getting torn down to the bare frame and powdercoated then reassembled once its cleaned up, i hope it looks presentable i'm restoring little pieces each day. I also have an extra airbox and want to see if i can make a modern carb work on the bike, so thats the reason for me asking about this, i thought it was a more common swap...

[GPracer2500]

FWIW, the 99-04 400EX carb has an adjustable needle and normal slotted fuel screw. The 05+ carb has a non-adjustable needle and "D" shaped fuel screw. Niether are huge deals (especially the fuel screw) but if I was choosing between two carbs, I'd want the adjustable needle.

The 99-04 needle does drop right into an 05+ carb.

[Dirtcrasher]

It IS a common swap, I don't know where the bananaheads are that have done it are in these last few topics....

I'll just do a search and see whats up....

[NOS_350X]

I have put them on MANY 350x's and its a must for any of them with more than a pipe and filter, BUT even on a stock machine it makes a world of diffrence. If you need any help just ask me like i said i have done many of the swaps. It fits a bit tight but nice. Use the search or ask me I got all ya answers.