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Discussion Starter #1
I have a 92 GSX-R 750. I changed the spark plugs in my motor bike, which requires the removal of my gas tank. After replacing the plugs, she started running good. I let her idle for awhile, and she didn't sound very good. As soon I'd bring the choke down it would die. I took it for a short ride and it was completely gut less, had hardly any pull to it.
 

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Sounds like you may have kinked a vent tube....open the gas tank lid and if you hear a hiss or the bike runs normal you pinched the tank vent tube....or you might have kinked the fuel hose....also check to see if the fuel tap is open
 

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Discussion Starter #4
oldgixxer said:
Or the fuel system could be air locked. Open the carb drain screws and see if gas runs out freely.

I'm a bit dumb, if I open the carb drain screws (i'm guessing these are the two little screws on each side of the bottom of the carb) what am I going to see, or should I be looking for?
 
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a 92 750 has a vacuum diaphragm in the fuel petcock with a hose to carb boot #3. make sure it's connected properly to the back of the petcock, and to the carb boot. see if the petcock is set to either on or res. you may have to set it to prime first, to get gas back into the carbs. the gas lines come out either side of the petcock. there should be a spring on each line, which will help to prevent kinking. double check the lines. i had some trouble in the past with them.

the tank vent tube is out the top of the tank. hard to kink that.
 

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Most carbs have a philips head screw near the bottom of the bowl. Your carbs could be different. Any bike I've had has had drains. When you back it out a turn or two gas will drain via a hose routed out the bottom of the bike. This will also clear air in the system usally. It is the easiest first step to diagnose a fuel problem.
 

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Sometimes there's no hose off the nipple on the bottom of the float bowl by this screw. If that is the case then it'll drain out over your engine unless you hook up a temporary line.

Morphiend, you're getting really, really close to being someone that should be getting a service manual. It's by far the best accessory money you can spend on your bike if you want to do more and learn more about this suff.
 

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Discussion Starter #8
thanks for all the help guys, I went on gixxer.com with some problems with my bike, and didn't get same kind help i've recieved here. as for the service manual I do have one, in pdf form, which has helped out quite a bit. I took the bike out today for a short ride, gave a little burst on pri when I first started her, she started fine, idled normal. I took her for a ride and she was riding normal, got her up to about 110km in the normal time it takes, then as soon as I left off the gas she stalled out and would not start. Had to coast her back home and then she didn't want to start. My girlfriend gave me grief about working on her so I had to just park her, but I'm pretty convinced that something to do with the petcock, since giving it a shot on prime seems to fix all the problem temporarly. I'll have to stew over it till next weekend when i can go back to Squamish and work on her again, but any advice based on that would be great. Thanks again for the help
 

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Discussion Starter #9
I've opened up the screws on at the bottom of the carbs and they ran fuel freely, with the gas tank already off. Once I had the gas tank off I noticed that one hose, the one at the back that runs down to the bottom of the bike from the lower back side of the tank had obvious signs of kinking, though I'm not sure if this would affect the bike's performance any that manner, and I'm not sure that i didn't kink it like that when I was pulling it off. If I mixed up the fuel lines on the petcock, could that cause these kinds of problems?
 

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Hose order is certainly important. Read Doug's reply above. It's all there.

If you're sure that you got the vacuum line to the petcock set up right then it may be that your petcock isn't working right any more. Since your fuel flow problems stem from you removing and replacing the tank double and triple check your work since you may be misplacing the vaccum line somehow.

You can check for proper petcock operaton easily enough. Disconnect the vacuum and fuel lines from the carbs and bend them out to where you can get at them. Put the gas line into a jar and the vacuum line into your mouth. Suck on the line about as hard as you do for drinking soda through a straw or a touch more. Gas should flow out the other line into the jar about fast enough to fill a beer bottle within a minute. If you need to suck particularly harder than that or if you seem to be sucking air through the vacuum line then you have a bad hose or petcock.
 

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Discussion Starter #11
i know i have the vacumm line on the right because it only fits on one of the nipples, but there is two fuel lines, and though i took note of how i took them if when I first removed them, i'm wondering if there is any way i might have mixed those two fuels lines up. my owner's manual isn't very clear on which line goes where. right now, i'm emptying the tank of the fuel that's in there and i'm going to put fresh 91 oct in with some carb cleaner and run it through, just so i know its not just some water in the tank or something.
 

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Discussion Starter #12
ok so i just tried sucking through the vacuum line and with the petcock set to on, next to nothing came out, then as soon as I switch it to reserve, gas would flow freely from either fuel nipple. so from what I understand it sounds like something is wrong with my petcock on 'on' or am i off base here. if not can i run the bike on 'res' ?
 
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