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View Full Version : Jetting 101....Gearing 101....Rev-Limiter basic training....HELP



"BLAHH"300!!
07-16-2003, 05:31 AM
.....130, and 135 main jets on hand.
.20 over hi-comp Wiesco
WEBcam "all-around"
uni filter
Four 1"hole's in Box-Lid
D.G. RCM complete
Stock revlimiter
...Mississippi, (highest elevation is 900ft.) i'm about 600'-700'

with that said, what should my jetting be?
...I back fire on deceleration, and it cut's out at high RPM's.
I can't tell if i'm cutting out b/c of the rev limiter,
...Or if it's not jetted corectly.
Sometime's i can stab the throttle, and it'll rev,
...Sometime's i can stab it, and it'll bog, THEN rev....

(Backfiring Means ?)
....1 "Member" told me that 'bakfire on decel' means i have too much fuel, and it's not burning off properly, or eficiently. he said to go back to the 130, and use the "mix screw"
....Then i read a post by "Silverfox" and she say's bakfiring means it's lean....
....WHO"S RIGHT?
..(I've been talkin with the "member" for a while, and i feel like he know's his {300EX} ****..and Silverfox is a chic. So witch is the right answer?..
..(i'm ganna catch mud for that "CHIC" comment aren't i :uhoh:
(You know i love ya' :bandit: )

I installed the 135, and it started right up, but back fired on decel (with clutch both in, & out) then i talked with a that member, and He say's backfiring means it's getting too much fuel, (rich), so i put the 130 main back in, and played with the air/fuel screw. Still backfiring.

I'm still back fireing, on decel. WHY? i've turned the mix screw all the way in, then backed it out in 1/4" intervels ALOT.
(i felt like it was ganna fall out if i unscrewd it any further so i stopped.)

Where should i go from here? I'm pretty sure all quads are going to backfire a little after installing and aftermarket pipe, and i can't make the backfireing's (less noticable when i play with the screw.

...Part II : REV-LIMITER....( 14/38 w/t 20" rear tire's.)
How can i tell if it's the revlimiter, or if it's the jett that's making me cut out....
(i'll try to explain it)
(..1st gear..non-existannt really,)
(..2nd gear, cuts out right before i'm ready to shift.)
....(right when i decid i wanna pull the clutch, she cuts,
....i might even have my thumb off the gas already)
(3rd's kool, 4th cuts the same as 2nd. and 5th cuts so i let off, and pull the clutch....Race Is Over.

should i try a 36 rear sproket?, or a 13 tooth front?...(rather have the smaller rear. more clearance...36 rear would give me more top end right?

trueblue450
07-16-2003, 08:16 AM
put the air/fuel screw all the way in and back it out 2.5-3 turns and see that.. mine stoped backfirin when i did that.

"BLAHH"300!!
07-16-2003, 09:00 AM
.....Full Turns correct?....Thanx alot, i'll try that in just a minute.
Can i get you guy's to help me with these other 3 questions.

1: Gearing.........
..14/36 gearing would give me more top end speed right?
How much bottom end would i loose..
..1st gear is VERY low right now. Can barley turn the wheels over before it's time to change.

2: Rev-Limiter.....
..How can i tell if it's my Rev box, or my jetting that is making it CUT OUT.?

3: Plug gap. (300EX
..o.k. everyone of you guy's gap your plugs before you put em' in.
What is the proper gap for My 300, Tell me witch side of the Metal thing your reading fom. (little metal thing you "gap")..
...i Slide mine around the gapper untill the metal thing on the plug is right on the .40.....(the side closest to the FAT end of the gaper is on the .40....am i gapping it right?....(tell me witch side of the little metal thing your getting the reading from.

....Little more info, just in case you need it.
My Plug is TAN......It's Black on the threads, but it's tan on the white part...This same plug has been in thre since i put it back together. (6 ride's old)


(((....I prolly....nvermind, i KNOW i posted more info than you guy's needed,....ya'll are prolly used to it by now,...but i'm i and out today, an I'd hate to miss THE answer, B/c I didn't tell em' i ha hole's in my air-box lid......Sorry So Long.

TRX_Thumper
07-16-2003, 09:20 AM
first of all the main jet DOES NOT have anyting to do with it backfiring on decel...thats all in your pilot jet and fuel screw..i recomend sticking a 42 pilot in it and stick the 135 main in it...yeah 14/36 should be ok when i had a 300ex i really liked 14/38 that was always my fav and i never hit the rev limiter much...i think your hitin the rev limiter cause 135 jet is ok size for your mods...yeah you might be able to run a bigger size jet but get your pilot circuit fixed first then we will move onto the main jet...im gonna say keep the needle in the stock position...also NGK plugs are pregapped keep that in mind...and on the plug color thing al we need to know is what the color of the tip of the electrode is not the threads or anythign else...just throw a 42 pilot in there then go wide open down the road doesnt matter what gear kill the motor pull the clutch make a stop pull the plug and then post what color it was and i will help you dial the main in

"BLAHH"300!!
07-17-2003, 12:26 AM
.....Yu' da' man.!
I'll PM you later.
....(i'll try to make it short haha)
What size is the stock pilot jet?

TRX_Thumper
07-17-2003, 09:41 AM
stock pilot jet would be a 38

jgfarmsracer
07-17-2003, 04:48 PM
i put a 15 front sprocket on mine with the 20" tires and the 36 rear sprocket also have a 138 main with the air screw turned out 3 turns and 0.40 gap on the plug

also the air screw is different for every machine