need help with 94 yzf750 jetting

[clarythedrill]

hey everyone, need some help with my bike. it has a d&d slip on with a k&n filter and dynojet jet kit. heres the problem. the carb settings are: mains 122, needles are 2 down from the top with spacer, mixture screws at 2 1/2 out, and floats adjusted leaner. heres the problems.<br><br>the bike will not take off unless the revs are above 2500, if not it acts like it is going to stall. thats the reason the floats are adjusted leaner, about 3 mm from stock.<br><br>on a trailing or constant throttle about 7000, it studders like it has a lean condition. the needles are one groove leaner than the kit suggests, this done also to improve off idle response. the kit says the needles have alittle to do at that rpm also, and the dynojet tech said to do it. from 9000 to redline, the bike runs great, so im inclined to believe the mains are correct.<br><br>the bike has always needed the choke to start, even if off for only a couple of hours. even with the choke on, as the bike warms up, it doesnt rev up on its own like it should, telling you to turn the choke off. its just stays at about 900 rpm until you ride, then it idles fine.<br><br>and the last thing, there is a ton of soot around the end cap of the exhaust, telling me im rich, but everything ive done is to lean the bike out to improve off idle response. the plugs are not overly black, actually they are looking pretty good, lot lean or rich. so, how do i lean the bottom to improve off idle, yet richen the middle that i havent already done? any replies are greatly appreciated. thanks.<br><br> <p></p><i></i>

[flyingcircus68]

From reading your post, I would guess that your idle/pilot circuit is too lean. If you have to give it enough throttle to get above 2500 on take off, your starting to get beyond the pilot ciruit and into the territory of the needle jet. If your bike doesn't respond to the choke as excpected, and if at operating temp. the choke doesn't stall the motor, it's too lean. If it studders on trailing throttle, that is the zone partly to mostly controlled by the pilot circuit. I would do the following:<br><br>1 check the choke circuit as prescribed above<br>2. tape a third of the snorkel off, and see if that improves part throttle/low rpm. If not see if taping more off improves it. If it does, it is too lean. If not, it could be the converse.<br>3. If it is lean as I suspect, go back to the stock float level. If it improves the situation, try taping off some of the snorkel again to see if it further improves or gets worse. You might need to raise it a little higher than stock.<br><br><br>Jetting should be done in a methodical sequence. My suggestion is the following:<br><br>1. get the idle squared away by synching and mixture at stock.<br>2. play with the pilot circuit to where it accepts throttle just off idle. You should be able to apply throttle from idle and it should pull with no sputtering, pausing or hesitation.<br>3. play with the main jet to get good running from the top 3000 - 4000 of power band.<br>4. play with the needle to adjust the middle section. <p></p><i></i>