View Full Version : Bigger Main Jet?
rooster300ex
07-25-2005, 09:52 AM
How come the dynojet jet kit only comes with a 128 as its biggiest jet. i've seen some 300''s on here have a way bigger main jet then i have and have less mods then i do. i bet i need a bigger main jet to make mine run right. u can see my mods down below. do ya'll think i need a bigger main then a 128.
skyhighatv
07-25-2005, 10:01 AM
does it run good now? what probs are u having? backfire,sputtering or bogging out?
let us know more.
jak1389
07-25-2005, 10:04 AM
your sea level is wat determines what jetting you run with your mods. adjust your fuel screw to fine tune your jetting.
rooster300ex
07-25-2005, 10:05 AM
well it cuts out at lil over 1/4 throttle when holding a steady speed, and the throttle response isn't that great and say i was powersliding in 3rd it kinna bogs. it didn't use to when it was stock, and sometimes it will make that air spitting noise through the carb.
bwamos
07-25-2005, 01:15 PM
Bog at 1/4-1/2 throttle is a lean needle. Move clip down 1 (needle up).
Air being pushed back through the carb? If so, you're timing is off and that will make jetting really really weird.. lol.
rooster300ex
07-26-2005, 08:35 PM
can rejetting make your timing get messed up or what. i had the whole engine rebuilt it should be at the right timing.
jak1389
07-26-2005, 08:38 PM
no it wont mess up the timing but it could mess up the throttle response.
prepracing
07-26-2005, 08:45 PM
just an FYI - dynotjet # sizes are different than other jet # sizes, such as khein jet #'s. That always causes confusion on hear on all these jetting questions
rooster300ex
07-26-2005, 08:51 PM
u mean the timing being off could make it lose throttle response.
jak1389
07-26-2005, 08:53 PM
Originally posted by rooster300ex
u mean the timing being off could make it lose throttle response.
most deffiantly.
Jason250ex
07-26-2005, 09:03 PM
how do you move the "needle clip" i have taken my carb (250ex) apart at least 10 times and have never found an adjustment for it
rooster300ex
07-26-2005, 09:04 PM
well thats bull**** the guy that rebuilt it should take a look at it and make the timing right. could your jetting be so bad out of tune that it makes a puff noise through the carb. it happens when i tap the throttle, it puffs through the carb and dies.
rooster300ex
07-26-2005, 09:07 PM
if its anything like the 300ex carb the needle is in the slide. in the bottom of the slide in the middle u should see a small e-clip when u remove the slide arm. thats the needle move it down to richin and up to lean.
bwamos
07-27-2005, 09:23 AM
http://www.atvriders.com/articles/jetting.html
I'd still put money on the fact that when they put your engine back together they got the timing off by a tooth. It's really not hard to do. If they had the slack taken out of the tentioner side instead of the front side.. it will put it out of timing by approx. 2 teeth on a 300ex.
It's also a quick easy fix.
Have you had it up to full throttle under heavy load? If your timing is off by a couple teeth.. ot will feel like you have power potential.. but oddly feels like your trying to tow another atv behind you.
rooster300ex
07-27-2005, 12:54 PM
what do u mean under heavy load?
bwamos
07-27-2005, 02:16 PM
Shift into 4th or 5th gear early.. and give it full throttle.
rooster300ex
07-27-2005, 06:45 PM
oh i see. well i moved the needle down 1 notch to richen turned the fuel screw out 3 turns and cleaned the carb real good. i let it idle for awhile and it didn't cut out when i blipped the throttle. well see what happens when i ride it and get it hot.
rooster300ex
07-30-2005, 12:54 AM
i let it idle for awhile and let it get warm and it didn't cut out when i blipped the throttle twice at about half throttle. just gotta ride it nedt and check the plug.
bwamos
08-01-2005, 09:23 AM
Cool.. must just be jetting then.
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