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NOS_350X
05-06-2005, 06:24 PM
Has anyone put a 400ex carb on the 350x? I just put it on and it fits there nicely, and changed the sound ALOT. But i dont know where to start with the jetting. I was wondering if anyone has a done this and could give me a jet size to start with.
BIGCRIP28
05-06-2005, 06:53 PM
maybe the stock jet size for a 350x?
NOS_350X
05-06-2005, 07:44 PM
Well, the 400 has a 180 stock, and i put a 160 from a 350x in it, the only thing is there a diffrent style of jet.
Dirtcrasher
05-06-2005, 09:46 PM
160? isn't the stock 350X jet a 138?? Thats quite a bit richer I would think. But you have just opened up my eyes to yet another 250SX upgrade!!!
NOS_350X
05-07-2005, 12:29 PM
Well i know that a 138 would be way lean. I bet that the 400ex carb wount work very well on a 250sx, your probably better off looking at a 300ex
BIGCRIP28
05-07-2005, 03:15 PM
do you have any mods on it?
Blown 331
05-07-2005, 05:03 PM
I would think the stock 400 jet may be close. The 400 does breath better and has more cc's to feed but it the air supply is really restricted compared to the 350X. I bought a new 400EX in 2003 and I put a jet kit in it when I removed the air box. I can't remember what the stock jet was but it was WAY smaller than 180. The 450R's only have a 118 stock, when you take the air box lid off that you go up to about a 185, that just shows how restricted the new quads are on the air intake side, exhaust is about just as bad.
NOS_350X
05-07-2005, 07:53 PM
do you have any mods on it?

Exhaust, (no airbox lid), K&N, and other little things to make it run perfect. The carb was hopefuly the finishg touch power wise for a while. (i dont want go to a big bore kit until it blows up)

Blown, you also got to rember the type of carb on the 450's even with a smaller jet it can suck more gas.
ewalker302
05-09-2005, 01:24 AM
The stock 400ex main jet is a 148.
NOS_350X
05-09-2005, 01:37 AM
Ewalker Pm sent.

This week i'm going to try to dial this badboy in. Once i do that i'm going to post feedback on that modd. Then the next thing to come is a complete 350x exhaust feedback, But i need somone to trade me a DG muffler for a Cobra one (i got 2 dg's and need the cobra for a complete comparison).
HRC1
05-10-2005, 01:41 AM
how did you fit it into the stock carb boot? I am adding one to mine after i get the new cam installed. And i held it up to the boot while it was off the bike and it is about 4 mm too big.
NOS_350X
05-10-2005, 01:49 AM
Get new hose clamps, the boot on the engine is alright. The one that goes to the airbox is a little more tricky. Im still having a little trouble with the lower rpm's. From an idle when i open it up the coughs some, that acclerator pump is giving it too much gas. I'm still working on it, ill get it before this weekend. The main thing is you cant fit the hose that goes from the down tube to the airbox. The carb is too big for it.
NOS_350X
05-10-2005, 10:46 PM
Ok somone with one of these carbs, how do i adjust the acclerator pump? Its flooding out my x and i'm to the point i dont know what to do.
OldSchoolin86
05-10-2005, 11:08 PM
What pilot jet do you have in there? Stock is 38.
NOS_350X
05-10-2005, 11:25 PM
35 pilot, witha 138 main with the needle clip on the seond to top positon.
OldSchoolin86
05-10-2005, 11:42 PM
There's something about a throttle valve synchronization adjustment in the book that I'll try to scan for you in the morning.
NOS_350X
05-11-2005, 12:40 AM
Thanks, i would love you for that. It may not be my problem, but hopefuly it is and will help. At this point i have no idea what to do.
OldSchoolin86
05-11-2005, 01:05 AM
I better do it now so I don't forget. There was nothing else in the book besides normal stuff.

EDIT:
The second pic is the first page, you'll have to expand it to full size to read it if your browser auto fits it.
gary.h
06-03-2010, 04:51 PM
BUMP on this thread.....

OK You guys that did this swap (400ex carb to 350x)... what jests did you have to go to... Where you able to use the stock 400ex jets???
NOS_350X
06-03-2010, 05:01 PM
I have probably done this to 10 or 15 X's now,

It is impossible to jet from the keyboard. You have to just try it and see how it does and change jets acording to how its running, plug chops and other ways to tune the enigne.

Some i have had to go up on jets from stock, Othes go down. There are too many factors to just tell ya what to try.
gary.h
06-03-2010, 05:10 PM
I have probably done this to 10 or 15 X's now,

It is impossible to jet from the keyboard. You have to just try it and see how it does and change jets acording to how its running, plug chops and other ways to tune the enigne.

Some i have had to go up on jets from stock, Othes go down. There are too many factors to just tell ya what to try.



thanks for the feedback.. I will just plug test tell she gets close.... When you adjust the main do you also have to adjust the pilot jet???
NOS_350X
06-03-2010, 05:19 PM
whatever your runnin with the stock carb on the pilot, Go up one size and check it.

(every one has had to raise one size up on the pilot) The acclerator pump will flood it when stabing the throttle from and idle, but just a hair above an idle it will take off perfect.
gary.h
06-03-2010, 05:22 PM
whatever your runnin with the stock carb on the pilot, Go up one size and check it.

(every one has had to raise one size up on the pilot) The acclerator pump will flood it when stabing the throttle from and idle, but just a hair above an idle it will take off perfect.

Great Thanks...
gary.h
06-10-2010, 02:14 PM
Well i got my 400ex carb hooked up, Seemed to be OK, But won't start with the choke on???? Does this mean my Main jet is possible to big or my pilot jet to small? Had a hard time getting it to idle. Had to adjust out the throttle cable. What would you guys recommend I do from this point? Go Up on the Pilot? Or down on the main? or both.
Thanks in advance just trying to get some insight before i mess around with it tomorrow.
NOS_350X
06-10-2010, 02:18 PM
If a bike is tunde perfect you dont need the choke.

I NEVER use mine OK, rarely
NOS_350X
06-10-2010, 02:20 PM
As a matter of fact, You can unscrew the 2 screws and remove the choke flap, It is extremely common. I did it when i was running the ex carb on my X.

The screw can come loose and your engine eats it, And that is never good.
gary.h
06-13-2010, 12:42 AM
Quick question, When i go from idle to wipe open on my thumb throttle real quick my trike seems to not want to take it, seems to hesitate or all most die, What changes can i make to adjust this or is this a common insue with a bigger carb. Seems to do great when it is a little wound or a high idle, it takes full throttle fine, but from an idle not so. Thanks guys.
NOS_350X
06-13-2010, 02:58 AM
Its common with the acclerator pump
gary.h
06-13-2010, 11:57 AM
Cool sounds good then........ Got it dialed......... used your advice and changed the pilot, i just put the one from the x in, the stock main(ex) seems to be doing good need to throw my dirt tires on and do some plug test.. Thing starts easier now with out the choke than it did with the original carb, choke on... The one thing i have noticed is as soon as the trike gets shut off about 20 seconds later the carb will start to leak a little out the over flow... No big-e i just turn it off
gary.h
07-14-2010, 03:46 AM
My brother has done the carb swop, He said when he hit's 6th gear his trike spuders and will not go any faster. My question is what do you think can cause this??

And NOS 350x, was it you that said you can put a 14 tooth front sprocket on with a case saver as long as you do it at the same time you put on your sprocket??
jensenracing77
07-14-2010, 05:27 AM
My brother has done the carb swop, He said when he hit's 6th gear his trike spuders and will not go any faster. My question is what do you think can cause this??

does this happen at WOT. if so then it should happen in any gear. most of the time this will mean the main jet is to big. he needs to do a WOT plug reading.
NOS_350X
07-14-2010, 05:12 PM
i just put on 2 in the last 2 days, with the case savers. The chain will rub the saver but it wont hurt anything. basically set the saver in place (not the cover part just the saver) the roll the chain around, It will be tight but will work and fit. The other way is to put the saver in the center of the chain, have the chain around the sproket, the slip them both the sproket and saver into place.
gary.h
07-14-2010, 07:37 PM
does this happen at WOT. if so then it should happen in any gear. most of the time this will mean the main jet is to big. he needs to do a WOT plug reading.

he said just when he hits 6th gear. He pulled his plug today and said it looked like a rusty color, We are going to do some plug chops tomorrow.

I have noticed on my x with 20 inch paddles, stock gearing when i hit 6th it does not accelerate any more?? Just like an over drive. Is this normal with smaller tires??