air mixture screw question

[hondarider2006]

ok I got the dyno jet kit and did everything right. I jetted for an aftermarket pipe with no air box lid. I screwed the mixture screw 3.5 turns out, and fired it up. When it got to about 1/2 throttle, its started missing. So I figured I had the screw out to far. So I turned it in to 2.5 turns, and than it would barley even run. So I turned it out close to 4 turns and its almost perfect. Could this be my jetting or the mixture screw. I am running a 170 main jet with the clip on the needle on the 3rd position. Thanks in advance.

[sprtrx300ex]

170 main sounds kinda high, but i know that dyno jet #'s are different than other jet #'s. As far as the cutting out at 1/2 throttle, the needle jet needs to be adjusted. Do a plug check for each throttle range and go from there....

this should help you out.

http://www.exriders.com/jetting/jetting.shtml

[400exbiggun]

i think a 170 is high, i have a 160dyno with no lid also. We had a problem with my friends kfx, they said to turn it out this far, and put in this jet, it was something like a 155 (not really sure the actual sizes), but it was WAY to rich, and sputtered when he actually got going, so he droped it to like a 145 it was better:confused:

[cals400ex]

dynojet sizes are about one size bigger than keihin. so, a 150 dynojet is approximately a 152 keihin. you are way too big on the main jet. i run a 155 keihin jet in the summer months with a complete sparks X-6 system, no lid, uni air filter, and no choke. depending on your temperature and altitude, i would say run a 152 or 155 dynojet mainjet if you just have the pipe, filter, and no lid. you could also run a 42 pilot jet for better starting. the fuel skrew is for idle to 1/4 throttle. this should not effect your 1/2 throttle performance much if any at all. i would first change mainjets to get that in the ball park and then make other adjustments if need be. good luck

[dariusld]

I have the same setup and jetted exactly as dynojet said. I put the 170 main in and it runs fine. It's probably a little rich, but it doesn't stumble or miss and pulls strong.

the air mixture screw only deals with the pilot jet..and the pilot jet only deals with idle-1.4 throttle...so if its missing at about half throttle...your rich...also check and make sure your air boot didnt come off..mine did and it was acting very very rich right after 1/2 throttle..i couldnt even go anywhere unless i was at around 1/4 throttle..until i figured out the problem

[hondarider2006]

ok, well I don't really know what I did, but I played with the air mixture screw and it pulls hard, except when I barley give it any gas, it misses. I haven't done a plug check yet....(lost my spark plug remover...)so as soon as I find it I will do a plug check. Also going with a 42 pilot jet, what will this do for me, besides make it start easier? and where can I get one? Also, if I do get the 42, will it effect my main jetting in anyway? Thanks for the help guys.

[cals400ex]

the pilot will help from idle to 1/4 throttle. so there isn't much benefit besides starting. however, the bike won't run lean at idle anymore. you can just get the pilot jet at a local dealer. just tell them you want the keihin 21 series pilot jet with the size being 42.

[carlj75]

I am running the 170 dynojet and I followed all of the instructions that came with the kit. I also jetted 3 of my friends 400's exactly the same and they all run really good. Was your quad all the way warmed up when it was running bad?

ok i think i kno what ur problem is. I just got finished fine tuning my 400 after i put on a K&n, Hmf slip on, 5 uni airbox vents, i put in a stock 170 mj, and I put my needle clip all the way down. It would hesitate at barley any throttle to about 1/4 i thought it was the air fuel screw i was wrong. It was the Needle clip. I raised it up one from the last position and it runs GREAT. I left it a lil rich but thats better than lean. Check ur needle clip.:) ;)

[JabberJaw]

air mixture screw question

Mixing air has nothing to do with 'screwing'... you need alcohol for that!