What I've learned.
I am new to these forums. I just bought a '92 VN750, and am having a problem with fuel flowing out of the carb vent hose behind the right air filter assembly. I have read through almost all of the threads which look to address similar problems, and between what I've read and what I figure the problem to be, I think I have found the problem and solution.
Sounds to me that there is a stuck float or float valve. I have put several ounces of SeaFoam in a fresh tank, and run it through, let it sit a day, and noticed the motor starts better, but the fuel still flows out of the vent, maybe even more now. I noticed that the bike runs really well when I turn the petcock to OFF, that is, until it runs until it conks out from running out of fuel. Also, no fuel comes out of the vent hose with it on OFF. When I turn it back to ON, the bike sputters, runs rougher, and the fuel comes out of the vent hose.
A little history on the bike. One owner, meticulously serviced. Was put away 2 years ago and not ridden or even started due to an injury. Previous owner says she put Sta-Bil in when she stored it, and prior to that it always started easily and ran like a top. (This is a good friend, and I have seen the bike when it was running, so I know this to be true.)
So, I am planning to try again tomorrow, after the SeaFoam has sat another night, and if it's not better, I will drain the tank, and run straight SeaFoam through the carbs, let that sit for another day or so, and try again. I would rather not pull the carbs unless absolutely necessary, as, like I said, I can get the bike to run really well with the petcock OFF. I pulled the petcock, and cleaned it, and it works properly. I also removed the gas cap, cleaned the vents on that, and made sure the vent line for the tank was clear as well. Does anyone have any other suggestions for me?
Here's a little history on my bikes. I also have owned an '86 VN750, so I am fairly familiar with the workings of these bikes, as I had a chore keeping that one running well. During my searches on these forums, I've noticed several people mentioning the fuel petcocks, and there seemed to be some confusion. The '86 had a PRI-ON-RES, while the '92 has OFF-ON-RES. They switched to that one starting with the '90 models, I believe. The PRI setting does stand for PRIME, and allows the fuel to flow without a vacuum, without the motor turning over. I am intimately familiar with this because I also own a Yamaha Virago which also has PRI, and I left it sitting for the winter on PRI once. When I tried to start it in the spring, the starter would not turn the motor, as if it was seized. The cylinders had filled with fuel, I simply had to pull the plugs and crank it a few times to clear them, but that was 700 cc's of gas wasted, heh.
Well, if anyone has any other ideas for me before I decide to pull the carbs, I would appreciate it. Thanks.
Last edited by medic274; 05-01-2007 at 10:45 PM.