Help!!! Carb troubles...

[doof432]

Alright, I asked this in the rejetting topic and have not gotten a response, so sorry for the repost, but I really need to know something by tonight if possible...


I have a 96 750 that I have put a full exhaust and K&N pods. I think I have found the correct jet - 120. I have the needles at level 3 now and think I need to go down to 2. The bike hesitates at around 2500-4500 rpm. The main problem is, the bike will not idle. I have very thoroughly went over the seals and there is not a vacuum leak that I can find anywhere... I will not idle at all unless you keep it slightly revved up... You can twist the throttle and take the rpm to 3500 or more and it works perfect and then on the way back down, the r's stop at 2500 and stay there for about 10 seconds, then it drops down to about 600 rpm and dies.

One last problem, at the bottom of each carb is an... not really an overflow, it comes out the top of the carb, but these are the four 1/4 inch pipes coming out of the bottom of the carbs. They leak gas after you start it or run it for a while. Do I just plug that??? Please help me, I have done everything I can think to do to fix it. I have rejetted several carbs before and never had this trouble before now... Thanks

[Court93kat]

Idleing problem... Check the mixture screws. Try turning them out 1/4 turn and see if that helps. Also, have you tried upping the idle adjustment? Sometimes the simple stuff escapes us.

Fuel Leak... If they come out the BOTTOM of the carb, that is the fuel inlet. The vent tubes are at the top of the carbs, and look kind of like fuel inlets. If there is fuel coming out the vent tubes you have a float problem. You may have to open them up again to check the floats.

[hardlydangerous]

The hanging idle, and low rpm hesitation is a sure sign of a lean mixture. Chances are your mixture screw settings are still too lean. You can adjust them richer 1/2 turn at a time. if mixture screw adjustments don't work then you are chasing and air leak.

The fuel leaking out of the vents is a sure sign of either incorrect float levels OR dirty/sticky float valves. Either way the carbs have to come off for a cleaning and float check/adjustment.

You can clean the float valve seats using a Q-tip and some metal polish, then wash out any metal polish or dirt with a spray carb cleaner. I use a 1/2 a Q-tip in a drill tool and turn the dremal on 1/3 speed and use very light pressure (almost no pressure) let the polish do the work.

[doof432]

Do all four mixture screws need to be turned or just the one on the right side???

The float moves perfectly and is where it was from the factory, do I need to set it? how? how much??? And what is this about the inlet tubes at the bottom? (I am not at all critisizing and love the help, just reasoning) The gas inlet only has two tubes and I thought/think that they go inbetween carbs 1 and 2; and 3 and 4. There are the four outlet tubes coming out of the bottom of the carbs... There are the actual drain tubes coming out of the same areas as the inlet tubes, but these on the bottom, I don't know what they are for. There is nothing hooked to them and it only leaks out of number 1 and 2 carbs. It started leaking out of the number one carb and I put a little plug on it and then 2 started leaking so I put a plug on it, but then gas started leaking out of the air filter insted.....

Back to idle. Again thanks for your help, but why does it rev up and stay revved up and then die? what would cause the r's to stay up like that? Also, it smokes when you crank it as if it is too rich, but it runs as if it is too lean....

[Anonymous]

ok the 4 brass tubes your talking about are cali model vapor return hoses to the carcoal canitster leave them up plugged and if you got fuel runnign out of them your floats are jacked you need to reset them thats also why it wont idle without holding the throttle open a lil and why its smoking on start up its dumping fuel bigtime

[doof432]

ok the 4 brass tubes your talking about are cali model vapor return hoses to the carcoal canitster leave them up plugged and if you got fuel runnign out of them your floats are jacked you need to reset them thats also why it wont idle without holding the throttle open a lil and why its smoking on start up its dumping fuel bigtime

sounds real good... Thanks so much for the help. I did forgety to mention that it was a cali model. I stripped all that cra* off of there... But is didn't start leaking until the jet change, so it works good without it, but anyway, how do I reset the floats. Could someone please give me very detailed info on what exactly I need to do. Sorry to be so dumb about this. If you ever need help rebuilding a 440, I can tell you that, but I do not understand how the Japs (no disrespect at all) get all these tiny little parts together....... Thanks for what you ahve told me so far, and thanks in advance for the float help.

[The CyberPoet]

Doug771's "How to Set Float Heights on a pre-98 Katana"

Cheers,
=-= The CyberPoet

[doof432]

Doug771's "How to Set Float Heights on a pre-98 Katana"

Cheers,
=-= The CyberPoet

beautiful!!!!! Thanks alot..... I have been stuck on the R1 for a month now because I cannot get the kat to run right..... I am about to decide I should have left it stock..... I will try all this tonight and let ya'll know what happens. Thanks for the help and for that outstanding link...

[fordfurious]

mixture screws is exactly what i was thinking

[doof432]

one mroe question... when changing the mixture screws, do you put all four up to the 2 and 1/2 turns or just the first one?

[doof432]

one mroe question... when changing the mixture screws, do you put all four up to the 2 and 1/2 turns or just the first one?

Never mind on that one... I got it running great now, but... Now it will idle and it does not flood anymore and will idle all day long, but once you give it throttle it revs up to about 2500 rpm and stays there for different amounts of time ranging from 3 seconds to 1 minute. After I went for a ride with it and it got hot, when I came back it would rev to 3000 insted of 2500 and stay at 3000... What is that???

[The CyberPoet]

...but once you give it throttle it revs up to about 2500 rpm and stays there for different amounts of time ranging from 3 seconds to 1 minute. After I went for a ride with it and it got hot, when I came back it would rev to 3000 insted of 2500 and stay at 3000... What is that???

Sounds like a sticking or overly tight throttle cable.

Cheers,
=-= The CyberPoet

[doof432]

really??? I figured it was something not set quite right..... I will try that in the morning and keep you updated. Thanks for checking back in on me, I will probably still need a little help with this tomarrow, and hopefully it will be right then. I made major progress tonight, it runs nearly perfect.
Thanks again...

[md86]

Try this ..... back your idle adjuster all the way out and rev it . Still doing it ? Here's my logic .... On our project bike (coinmcidentally a Ca Kat 750) , the idle was sticking like that . I backed the idle all the way out , and it stopped doing that , but would not idle . Crap in carbs .

[doof432]

Try this ..... back your idle adjuster all the way out and rev it . Still doing it ? Here's my logic .... On our project bike (coinmcidentally a Ca Kat 750) , the idle was sticking like that . I backed the idle all the way out , and it stopped doing that , but would not idle . Crap in carbs .

I figure it is something to do with the idle adjustment... It runs at about 1100 rpm when it's not revved up (of course) and that is about perfect for me, but I can turn that idle adjustment forever and it does not change where it is idleing at. so I will try that tonight. All the way tight with it or loose all the way???