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View Full Version : A couple questions about SX jetting with a 350x carb


Tri-ZNate
08-17-2005, 10:15 PM
ok I have a 350x carb comming for my SX. I plan on putting a supertrapp exhaust on it along with a K&N filter. What jet do I need to run with no mods and what jets should I run with the modds listed?
nouseforaname90
08-17-2005, 10:38 PM
I was just about to post a thread about the same thing. I was wondering what the jetting should be with a SuperTrapp, K&N air filter, and with the air box lid off. And would it be worth it to put a 350X carb on it??

I'm not meaning to hi-jack your thread.. but if someone answered either of our questions, it should help the other person. lol.
Tri-ZNate
08-17-2005, 11:41 PM
And would it be worth it to put a 350X carb on it??


ill let ya know when I do it. im gonna run the same setup (forgot about the lid not being on). I may also run with the ram air hose unclamped and running outside the chasis.
nouseforaname90
08-17-2005, 11:47 PM
Ok. Sounds like a plan. I know for a fact that just taking off the air box lid helps alot as far as speed. But I haven't ran my SX with the new SuperTrapp on it (well... acutally I haven't ran my SX for about 3 months due to it being in pieces for the restore.. and I haven't ran it with the SuperTrapp period), so I don't know how much the SuperTrapp will help either.. but I figure it would be worth puttin a 350X carb on it.
Tri-ZNate
08-17-2005, 11:53 PM
I figure if your gonna do modds like piping, a proformance filter, and air box modds it would probably help to put a bigger carb on.
so-cal
08-17-2005, 11:56 PM
I have a supertrap and am getting a 350x carb to do the same as you guys (no lid for me). There was someone that ran stock jetting but I think he had a cam and headwork done, I think he had a high compression piston as well.
Tri-ZNate
08-17-2005, 11:59 PM
cool let us know know how it comes out.
conig
08-18-2005, 12:31 PM
Ive been looking for this information as well.
TeamGeek6
08-18-2005, 02:10 PM
For the same size engine (same airflow) the jetting shouldnt change much. Bolt it on and check the idle mixture by adjusting the air screw (if it has one) and that might give you an idea of what to do on the rest of the jets.

If that doesnt tell anything, warm it up, block the throttle open a little and turn the gas off. If its rich, the engine will speed up as the carb drains. Dont let the engine overheat...
OldSchoolin86
08-18-2005, 02:31 PM
Not be an ass or anything but to be honest that's too much carb for a 250sx. You're going to loose too much low end power to justify your minimal upper RPM gains. The trade off will not be worth it. I'd look for a 300ex carb.
conig
08-19-2005, 10:40 AM
my understanding is the 300ex is the same size carb as a 350x it just has an accelerator pump. I was planning on using a 300ex carb.

Am I wrong.
OldSchoolin86
08-19-2005, 01:51 PM
my understanding is the 300ex is the same size carb as a 350x it just has an accelerator pump. I was planning on using a 300ex carb.

Am I wrong.
IDK why, I thought the 350x was bigger. Apparently from the info gave in my thread the 350x carb is a 31mm. The 300ex does have the accel pump and is a 32mm. Sorry 250sxwheeliepop, didn't mean to pass bad info. :(
Tri-ZNate
08-19-2005, 01:53 PM
IDK why, I thought the 350x was bigger. Apparently from the info gave in my thread the 350x carb is a 31mm. The 300ex does have the accel pump and is a 32mm. Sorry 250sxwheeliepop, didn't mean to pass bad info. :(

I was gonna try to use a 350x carb anyway
:lol:
bigredhead
08-19-2005, 01:57 PM
I am really curious to know how this turns out ...

Anyone ever try using 23.5 tires on their SX ?

I plan to hop up my SX to the moon as well over time.. but other than increasing RPMs i don't see any way of increasing top speed over 55 ish.
Tri-ZNate
08-19-2005, 02:01 PM
in the 300ex on 250sx thread there were some links and it appears that with a high flow air filter and a supertrapp exhaust the jetting is about right. otherwise you can take the jets from the SX and put them in the x carb.
OldSchoolin86
08-19-2005, 02:03 PM
I was gonna try to use a 350x carb anyway
:lol:
I'm sure you were but I was just offering my appoligies. That 400ex carb though is way too much.
Tri-ZNate
08-19-2005, 02:05 PM
I'm sure you were but I was just offering my appoligies. That 400ex carb though is way too much.

yeah I'm gonna see if I cant trade it for an X carb. hmm or see if my sx jets fit.
OldSchoolin86
08-19-2005, 02:15 PM
yeah I'm gonna see if I cant trade it for an X carb. hmm or see if my sx jets fit.
http://www.3wheeler.org/vb/images/smilies/doh.gifLMAO, ok man. I thought you wanted more power though? If you do you're going the wrong way with a 35.5mm carb on an SX. :lol:
Tri-ZNate
08-19-2005, 02:27 PM
http://www.3wheeler.org/vb/images/smilies/doh.gifLMAO, ok man. I thought you wanted more power though? If you do you're going the wrong way with a 35.5mm carb on an SX. :lol:


I'm still not totally convinced its a 400 carb. So it depends whe I get it, if its smaller than a 400ex ill use it otherwise its getting sold.