Modding A Stock Carb

[400exJOE]

I have heard a couple of times on here of peeps "modding" their stock carbs. I am soon to get a 440 and was wondering if there is anything I can do to the carb in addition to jetting. I have a Supertrapp IDS2 silencer and a K&N. Its got a 155 main and a dynojet needle right now. THANKS

[mikeboone]

You can eliminate the choke. It restricts the air even when it is flipped up not in use. Just take out the two small screws on the plate when you take the carb off and it will fall out. You really must put in a larger pilot jet such as a 42 or 45 to compensate for this so the quad will start esp in cold weather. Also; drill a couple one inch holes in the airbox; not directly over the filter though. If water gets in; it wont be a straight shot to your k&n. With a proper main jet; this will greatly help acceleration.

[Tommy 17]

i have mine mod i dunno what he did to it but its really polished inside of it now when u look into it. i still have a choke 2... he did something that makes it look swirly inside i dunno what it is i will ask him...

[MichaelS693]

your carb was prob. port and polished

[redrider ex]

mikeboone the part about taking out the choke is a good idea
for me because here latly when i land from a jump or ride really
rough the choke lever has been falling down to half trottle and making the motor run bad , i was hill climing last week and doing
fine then i started up the hill again and gased it hard and it cut out and i barly made it and i reached down and the choke was on
redrider ex:huh

[400exJOE]

could i port and polish it by myself w/ a dremel tool and the ride attachments? Does it gove any gains? I think removing the choke is out of the question for me. In NY it can get kinda cold in the winter.

[mikeboone]

I dont think you would notice much of a gain w/ just a polish job.

[DISHO1]

i have e-mailed curtis sparks about there stock 400ex carb mod and they did not tell what they did to the carb. i have e-mailed tom miller motorsports http://www.tmmatv.com/ about there carb mod and they told me more info about what they did. also i have sent a exriders member a e-mail about the carb mod he does for $75 ( i can not think of his name now :confused: ) and he gave me some help.


from the info i got from them and where i have searched they machine the upper part of the venturi to make it larger.i have looked inside my carb and when you hold it full throttle the slide is out of the way flush with the upper part of the venturi. if you machine the upper part of the venturi a few mm the slide will not be flush . the trick is how to get the slide to go up more so it will be out of the way. the slide will only go so far and it hits the valve arm that connects to the slide.

does anyone know what to do to the slide?

i have only removed the choke from my carb but if i could figure out what to do to the slide i would try to mod the carb myself.

[MichaelS693]

you could polish it with a dremil tool but i seriously doubt if u will notice a gain in power or ANYTHING

[callen74]

mikeboone,
I noticed you are from Rockingham. Just wanted to know if there are any good places to ride in your area.

[mikeboone]

Callen: I actually live closer to Mt Gilead; but we spend more time at the Rock. We do Drywall (sheetrock-acoustic ceilings-stucco-plaster-metal studs) and subcontract for Southern Builders--GR Kindley. I usually go to Uwharrie Mnt. It is closed from Dec 15 to first of March though. We have some guys from Lumberton help out on jobs; they are pretty good. Where you ride?

[stevengates45]

I got a stock smoothe bored carb & put it on a basically stock ex (header pipe, air filter) & noticed a power difference. I reccomend smootheboring it. But one thing. When I got mine done, the guy who did it bored it out huge. I compared it to a bone stock 300 carb & the intake was much much larger. Choke is also taken off. LIke i said though, i reccomend smootheboring a stock carb 100% if you dont want to spend alot of money. Just bust out the drimel & start shavin.

[JhallettEX]

Do you have to take your carb completey off to do this? How would you insure nothing falls into the carb. Thanks alot.