426ex jetting

[ww228king]

ok pro techs ....got a question....i have what is listed in my sig. and i was wondering what jet and needle hight

[GPracer2500]

Airbox lid? Snorkel? Elevation? Normal riding temperatures?

Experimenting for yourself will get you the best results.

I'd start with the needle in the middle position and work your way richer. Depending on your elevation, I'd be surprized if you're more than 1-2 clip positions richer than the middle postion (move the clip down to go richer). You can use a little flat washer to get half postions. The middle (stock) spot might turn out to be best.

For the main, I'd jet a range of Keihin jets--say 168, 172, 175, 178, 180--and figure out which provides the best WOT performace. Those sizes are assuming your at 500-2000 feet.

That's pretty vague advice, but there are just too many factors that affect that absolute best jetting specs for anyone to really tell you precisely what your bike needs. Luckly, access to the main on the stock 400EX is very good. Main swaps take a couple of minutes tops.

[ww228king]

ok sorry for not giving more info.....air lid is off, i now have a dj 165 and was thinking of 170...i am about 140 miles from the nc coast so i would say elevation at about 500 to 1000ft.....i am running rocket fuel 114 leaded ...one quart per one gallon of 93...
i have heard of people putting a restrictor plates between the intake boot and the intake to have more lowend ....i brought home some stainless steel to make them from, really didnt want to lose my topend either....

[ww228king]

needle at 3rd from top...forgot that part

[69ss396]

I'm running stuff in my sig. and I'm using a dj 170 with clip 3rd from top 2.5 turns out on the air/fuel screw.. I'm also running my box lid with 6 uni plugs. Bike runs very good and does not bog.I have done a plug check. today in fact and it is very light colored so I may go bigger on the jet size...

[ww228king]

i just picked up a 180 jet today, so i will put it in tomarrow...let you guys know what happens

[ww228king]

WELL, TODAY I DID THE TEST...RUN IT HARD IN 2ND GEAR AND GRAB THE CLUTCH AND HIT THE KILL SWITCH....PULLED THE PLUG AND IT WAS WHITE....SO I NEEDED MORE FUEL...SO I WENT FROM A 170 TO A 180 JET AND PULL MY SNORKEL OFF....RUNS GREAT...SO I HAVE A 426 88MM 11:1, STAGE 2 CAM, PORTED AND POLISHED EXAUST PORTS AND SLIGHTLY PORTED INTAKE, 180 JET , FUEL SCREW 3.5 TURNS OUT AND AIRBOX LID OFF AND SNORKEL OFF...RUNNING 1 QUART OF ROCKET FUEL 114 LEADED PER 1 GALLON OF 93 PUMP GAS. PIC OF THE QUAD ARE HERE

http://www.exriders.com/vbb/showthread.php?s=&threadid=223080

[abuckley1290]

is the 180 main jet a dynojet or a kehin?

[ww228king]

kehin