GT550 Right cylinder flooding

[crazyeights]

Hello, I got my GT550 running and registered recently after replacing the top end due to 2 holed pistons (timing WAY advanced). I went for a ride and when I got back the right cylinder pipe was cold. The other two cylinders run great and have consistent temperature readings from the head. I took the right spark plug out and it was wet. So far I've re-checked the timing, checked for spark on that cylinder while it was running (good spark) and I checked the pipe for clogging. When I initially got it running the right pipe became clogged due to a mouse nest in the pipe, which has been cleared. I let that cylinder air out since Sunday afternoon (no spark plug, sris valve removed, throttle taped fully open) and today I put a new plug in, that cylinder ran for about a minute and the plug was wet again. Any ideas on what could be the problem? Could it be float height? Thanks in advance for any ideas or help.

[GTandcbr]

It does sound like you have a float bowl problem. Either the float level is too high or the float is sticking or is punctured stopping it closing off the flow of fuel. The float needle valve could have some debris in it.Another suggestion is the choke sticking open?

[crazyeights]

I adjusted the float height and the right cylinder ran for a while. I put the air box on and the cylinder flooded again and refused to run afterwards. Wet plug. Does the float height need to be adjusted again? Could a vacuum issue cause this problem? Would it be a good idea to put a carb from one of the other cylinders to test?

[Alan H]

I adjusted the float height and the right cylinder ran for a while. I put the air box on and the cylinder flooded again and refused to run afterwards. Wet plug. Does the float height need to be adjusted again? Could a vacuum issue cause this problem? Would it be a good idea to put a carb from one of the other cylinders to test?

If you plan on swapping carbs, swap the two outers, the jets are different on the centre. It does sound like a float problem though - either height, heavy/leaky float or valve.

[jabcb]

In recent years I’ve had 2 bikes with cylinder flooding problems.
Both were due to sunken floats.
It was easy to spot when I removed the floats. Some gas ended up in the bad floats & they were noticeably heavier.

[jeff g]

Did you rebuild the carb with aftermarket jets? Many aftermarket jets are not accurate in the sizing. Also, if you rebuilt using a kit, the jets may just be the wrong size.

If it's not a jet issue and your floats are good and set correctly, there are 3 things I would check first...

1. Is the choke plunger stuck open. That would allow a lot of fuel into the cylinder.

2. Do you accidentally have the vacuum line and fuel line swapped on the petcock? The carbs are interchangeable position wise, so you might have the vacuum line coming off the right carb. If that is the case, you are lucky that you didn't hydrolock.

3. Unlikely, but I've seen it happen. Are you running rack mount carbs on late model cylinders? If so, make sure that the hoses connecting the 3 carbs are installed correctly. If they aren't, you could easily have the vacuum of the right carb connected to the fuel supply of the center carb. When that happens, the right cylinder will run for about 30 seconds until it sucks all the fuel out of the center carb and floods the right cylinder.

[crazyeights]

I got the bike running good on all three. I took off all three carbs, checked all of the floats, and made sure all jets and passages were free. I reset all of the floats to 25mm. I was going off of the wrong measurement when I did the floats the first time back in August.

Did you rebuild the carb with aftermarket jets? Many aftermarket jets are not accurate in the sizing. Also, if you rebuilt using a kit, the jets may just be the wrong size.

If it's not a jet issue and your floats are good and set correctly, there are 3 things I would check first...

1. Is the choke plunger stuck open. That would allow a lot of fuel into the cylinder.

2. Do you accidentally have the vacuum line and fuel line swapped on the petcock? The carbs are interchangeable position wise, so you might have the vacuum line coming off the right carb. If that is the case, you are lucky that you didn't hydrolock.

3. Unlikely, but I've seen it happen. Are you running rack mount carbs on late model cylinders? If so, make sure that the hoses connecting the 3 carbs are installed correctly. If they aren't, you could easily have the vacuum of the right carb connected to the fuel supply of the center carb. When that happens, the right cylinder will run for about 30 seconds until it sucks all the fuel out of the center carb and floods the right cylinder.

I cleaned all of the stock jets and reused them. I am also running the early carbs.


I went for a 30 mile ride today and the bike ran great. Thanks for all of the help, that's what makes this forum so great.