400ex Carb on my 86 350x

[pizbrewin]

Hey guys - I see tons of info on here about putting a 400ex carb on the 350x. I need to do this but I really don't see anywhere where there is info on which year 400ex carb to get. 1999 to 2004 or 2005 to 2013. Do either have any advantages/disadvantages? TIA!

[kazander]

I am running 05 and up with the 400 air tube and filter in the 350 airbox

[RIDE-RED 250r]

I'm bringing this thread back up because last time I searched there aren't too many good threads on this mod, although I haven't searched it in a while. I know the OP has successfully made the swap as well as a few others.

So I will be doing this upgrade to the wife's 350x as soon as the choke lever I ordered arrives.

Carb is currently disassembled and soaking in carb soak solution since last night. I will likely get it out of the soak, finish cleaning it and put it back together today.

Mods to her 350x are pretty basic,

1: Full DG exhaust system
2: K&N with Outerwears

From what the OP told me, he wasn't able to run the pipe that connects the airbox to the frame with the 400 carb. I'm OK with that, I deleted that part on both of my 250r's. Just need to be a little more frequent with air filter servicing.

Also, the OP told me that stock 400ex jetting was a near perfect starting point on his 350x. But his 350x is still bone stock including the exhaust. I suspect that I will need to step up a size or two from stock 400 specs on each of the jets.

I will keep this thread updated with how everything went and where the jetting settled out. The goal here is to have a good factual thread on this topic on how to get this done. Anyone else who has done it is more than welcome to chime in with tips, pointers and even jetting specs along with the other mods to their bikes. It would be nice to have a jetting database of sorts on this topic.

To be continued with pics and how-to. :beer

[RIDE-RED 250r]

Well, I got further with it than I expected to tonight thanks to the terrific hardware store I have just two miles down the road.

I was able to get the carb into the intake and airbox tube without heating them. The airbox tube was more stubborn though. I did need longer clamp screws as the originals were just not long enough with the larger carb in place. That's where that hardware store came in, I can't tell you how many times I have gone there taking a shot in the dark that they have some obscure little thing I need and they have it. Anyway, you will need 5x30 metric screws for the for the intake and airbox tube clamps and you will be all set.

As I have seen others say, the pipe that connects the airbox to the frame should be removed or modified so it doesn't press up against the choke on the EX carb. I opted to remove it as I removed the same piece from both of my 250r's and don't have a problem. You just need to be a little more frequent with your air filter service, especially if you ride in dusty conditions.

All I am waiting on is the choke lever I ordered last night.

From what I have been able to gather, stock 400ex jetting is 148 main, and 42 pilot and have seen some say that stock 400 jetting is very close, but maybe a pinch lean on the pilot. Since this 350x is running a full DG exhaust, and K&N filter and now has the pipe connecting the airbox to the frame removed, I opted to start with 150 main and 48 pilot, 2 turns out on the idle mixture screw. Remember, on these carbs the idle mixture screw regulates fuel, not air.

Despite not having a choke lever, I was able to fire the ol' girl up with her new carb. Started pretty easy, and I think the accelerator pump on this carb will be an asset for easier starting. A couple pumps of the throttle and it fired right up. Remember, this is my wife's ride and up to this time I have always had to start the thing for her hot or cold. Hopefully the accelerator pump makes it so she can start it herself. ;)

I did not however take it for a ride. I had a friend with a 400ex and for some reason his choke lever fell off and the engine would suck the choke butterfly closed while riding without the choke lever in place. I'll save the test ride till I get the new choke lever.

So in closing as far as how it sits now, this was a pretty easy upgrade in my opinion. From all accounts I have read it is a very worthwhile upgrade to the 350x.

Will follow up with a test ride report and any jetting changes I make if needed.

Pics of the carb installed. :)

[KDXRon]

I have the 400ex Carb mod. I deleted the snorkel and added outerwear to cover the snorkel hole to the air box. I went to lows and found a rubber boot in plumbing section that fit perfectly of the carb and intake boot. I then took a cut about 1/2 inch off the intake boot to offset the plumbing section. Added 2 metal clamps and it sealed up perfectly and I have no leaks. I had to take a drimmel and grind down the ribs on the intake boot to make sure I have solid seal.

Jetting is: 155 main and 48 pilot.

My bike starts with one kick, NO CHOKE cold. Idles and runs strong.


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[KDXRon]

Here is a video right after I installed the carb. Bike was cold when I started it.

https://youtu.be/6_3f5PbX5WI


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[RIDE-RED 250r]

Thanks for the tips.

In the interest of building this little database, do you have any other mods to your X besides the Supertrapp and header pipe?

Also if you get a chance sometime, would you mind posting pics of how you did the carb plumbing?

Nice looking front forks too... Jason Hall triples?

I also like your idea about the Outerwears to cover the snorkel inlet on the airbox... I might even have an extra one kicking around I can slap on there.

[Shawn Powell]

I did this to my bike also. I have no major motor mods other and a full exhaust. (Modified DG ) and a once over 10.25 comp wiseco. I left the snorkel tube cause I do a ton of trail riding with water crossings and mud. Takes a little massaging but it fits. Also left my air box and went with a 142 main and I think a 48 pilot. Stock clip position for the 400ex. Runs great. If I tossed my air box lid I could run richer get a bit more power but nah.


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