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Bike hesitates and stumbles. Also dies at lights.

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ANDRASTA

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Discussion starter · #1 ·
Hey guys , just wondering if anyone has had similar symptoms?

A few days ago I took all the fairings off including the gas tank. I decided to go for a ride so I mounted the gas tank and right off the bat I had problems Idling after I started it. I rechecked the fuel line and vaccum line and everything seems ok.

It idles ok now but when I ride it and come to a stop at the lights the rpm drops a bit and then when I go to take off the bike dies. The only way to get it to start is to move the petcock to PRIME. THe only way to stop it dying on the ride around the block is to keep it on PRIME. IT seems to run ok on PRI but stumbles and hesitates when set to ON or RES.

Another thing, Just a note, above 6000rpm I get all the bikes power back and pulls hard.

At crusing speed it stumbles and hesitates, dies at the lights, The only way to get it to start again is to put it back to PRI.

I have no idea what it could be. ANy suggestions?? THe bike is a 96 GSXR 1100.

THanks in advance.
 
#3 ·
petcock or the vacuum line to the petcock. Prime allows fuel to flow constantly whether the bike is running or not. When the petcock is in the reserve or on position the motor must be running for fuel to flow. I would think that it would be the vacuum line because your petcock isn't opening to allow fuel when the motor is running. Check that line, at both the petcock and where it connects to the engine. Make sure there are no cracks and make sure they are connected. You may have tugged on it a bit to much and it came loose from the engine.
 
#4 ·
here is a shot... I have solved similar problem in the past.

if you are taking the vacuum line from one of the carbs then it explains why you're bike works fine from 6000 up ( enough vacum to open the valve ) .

try changing the line to another carb and see what happens .

There also should be another place to take vacuum from before the carbs , that would be the best .

These are quick checks without taking things apart .

Keep posted
Trusty
 
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#5 ·
"malfunctioning petcock" - there's something I didn't expand on...

The diaphragm in those things can harden and not work worth a damn. You can likely locate a petcock rebuild kit that contains new o-rings and the diaphragm for $20-30.

Also, you can attach a hose to it and suck on it yourself. not recommended for riding conditions, but good for diagnostics. If you get a mouthfull of fuel, it feels like you're trying to suck start a Harley, or it won't hold a vacuum, then you have a bad petcock.

You can also confirm fuel flow in that experiment by detaching the fuel hose from the petcock, so you can see fuel come out.
 
#6 ·
The vacuum line on the 1100 should run off of a spigot on the intake boot of the No.3 carburetor (between the carb and the engine).
 

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Discussion starter · #7 ·
F. Richard Head said:
"malfunctioning petcock" - there's something I didn't expand on...

The diaphragm in those things can harden and not work worth a damn. You can likely locate a petcock rebuild kit that contains new o-rings and the diaphragm for $20-30.

Also, you can attach a hose to it and suck on it yourself. not recommended for riding conditions, but good for diagnostics. If you get a mouthfull of fuel, it feels like you're trying to suck start a Harley, or it won't hold a vacuum, then you have a bad petcock.

You can also confirm fuel flow in that experiment by detaching the fuel hose from the petcock, so you can see fuel come out.
Click to expand...
Excellent Ideas Richard, I never thought about actually sucking on the thing. Going to try that. Wait a min, that didnt come out right. HAHAHA>
 
Discussion starter · #8 ·
RoamingBison said:
The vacuum line on the 1100 should run off of a spigot on the intake boot of the No.3 carburetor (between the carb and the engine).
Click to expand...
Roaming BIson, is there actually three hoses in total that hook up to the Petcock??? Im only seeing two. I might have pulled it off by accident and not noticed. I know that there is a nipple sticking out in the middle of the petcock but I dont remember pulling a hose off that.

All I have is two lines. One going the right side and one to the left. Is it possible that I have the lines backwards??

WOuld it run if I had the lines backwards?? Im quite sure I contected them right as evidenced by the PRI position.
 
#9 ·
the two large ones are your gas down spouts. that little nipple is for your vacuum line to connect to. Without it connected to the vacuum line the valve probably won't open properly and starve your carbs of gas
 
Discussion starter · #10 ·
mofoka said:
the two large ones are your gas down spouts. that little nipple is for your vacuum line to connect to. Without it connected to the vacuum line the valve probably won't open properly and starve your carbs of gas
Click to expand...
SO there is 3 lines then??? Strange, I only saw 2 when I pulled the tank. Maybe when I lifted it a bit it came off and I just did not notice.
 
#11 ·
The vacuum line on the USA 1100 attatches to the top of the number 2 carb top. Maybe it pulled off the fuel petcock but is still attatched to the carb.
 
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#12 ·
I don't know the setup of your year, but I would expect two large fuel lines and 1 small vacuum line. You have likely failed to reconnect your vacuum line, which would explain everything.
 
Discussion starter · #14 ·
First of all,

I just want to thank everyone that gave thier input on this thread. All the information that was posted helped me diagnose and fix the problem.

Sure enough, I did not reconnect the vacuum line the bottom of the petcock. After I did, problem solved.

I posting a few pictures of the culprit incase someone looks at this thread in the future and has similar problems. I also added a video of the bike idling after fixing the vacuum line.

First the video.

ANd for the pictures as a reference.

Image


Image


Image


Image


Once again , thanks guys.
 
#15 ·
indeed, sincere thanks to you for the conscientious and helpful closeout to your issue!!
 
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RoamingBison
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