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need help hook up fuel lines

  • Thread starter Thread starter Anonymous
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Anonymous

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i just got done rebuilding my carbs for my 1978 gs550. I noticed there is 2 fuel lines comming out of the carb facing upward. I know the other 4 are for drainage. But my question is, where do i hook up the other 2 hoses to? i know one goes to the petcock, but which? and where does the other go? All the hoses between the carbs and the gastank have been disconnected. Hopefully she will run after this.
 
The smaller hose that connects to the engine side of the carbs connect to the smaller petcock nipple. The fuel line is the bigger one that connects to the airbox side of the carbs, between 2 and 3, I think, and connects to the larger nipple.
 
i have one fuel line hooked up to the small nipple and its running, but not to good. do i need to hook the larger one up on the petcock also? Another thing, i took it down the road, and it seems to have nice power, but when comming to a stop she wants to shut off, then i have to put the petcock in the prime position until it starts, then i can go back to on. any ideas? i also bought a carb sync tool, but i am unsure of what pressure to set them to. anyone know?
 
There are two fitting on the petcock. One is 5/16" diameter and the other is 1/4" diameter. 5/16" is the fuel line/connection. The 1/4" is the Vacuum connection. 10 inches of mercury at 1200 rpm should be just about right.

Earl


jman550cc said:
i have one fuel line hooked up to the small nipple and its running, but not to good. do i need to hook the larger one up on the petcock also? Another thing, i took it down the road, and it seems to have nice power, but when comming to a stop she wants to shut off, then i have to put the petcock in the prime position until it starts, then i can go back to on. any ideas? i also bought a carb sync tool, but i am unsure of what pressure to set them to. anyone know?
Click to expand...
 
there is no mercury in my carb sync tool, its four pressure gauges that hook up to the intake manifolds, and they read pounds of pressure. How many pounds of pressure should the carbs be? thank you all for your time. Will the bike not run right without the vacuum line hooked up?
 
Since the petcock/fuel valve is vacuum operated, if you do not have the vacuum line hooked up, then you always have your fuel turned off. Uhhh, no, the engine will not run normally without gas.

One inch of mercury is equal to .4911542 pounds per square inch.
So, 10 in Hg would be 4.91 PSI

Earl


jman550cc said:
there is no mercury in my carb sync tool, its four pressure gauges that hook up to the intake manifolds, and they read pounds of pressure. How many pounds of pressure should the carbs be? thank you all for your time. Will the bike not run right without the vacuum line hooked up?
Click to expand...
 
now there appears to be something wrong with carb #2 from the left. Every once in a while it spills a continuous trail of gas for a couple seconds then stops. It seems to be dripping a little. And when i put the petcock on reserve fuel drains out of the carb. carbs are so frustrating! any help is greatly appreciated.
 
If your hoses are connected wrong, gas will continuously flow into the carbs with the engine off. If the diaprhagm is damaged then there is nothing to prevent fuel flow with the petcock open. Pull off all hoses from the petcock and see if gas flows out with the fuel set to on. if no flow that is good, the diaphragm is ok. If set to prime then fuel should flow unimpeded. Once set to ON put a rubber hose on the small nipple on the petcock and suck a little. Fuel should then flow out the big nipple. Again the diaphragm is ok. No fuel should flow thorough the vaccum line. plug the vacuum into the small nipple on #2 carb. Plug the larger 5/16 line coming out of the petcock into the large nipple between #2 and #3 carb.
 
thank you all so much for your help. The ole gs is running ok, but i don't think all its power is there. Its got an exhaust, header, and bigger jets, but it still dosen't thrill me. it should at least pull the front wheel of the ground? it also likes to slip out of gear into a neutral that dosen't exsist at high rpms. Like theres a neutral between every gear.
 
You are going to find the gearbox more sloppy than the new bikes so just shift up hard for each gear. Mine shifts with a loud clunk but I know it is in gear. False neutrals are common on these older bikes. Not all that annoying once you are familiar with their personalities.
 
yes you are right. The more i ride the less it happens. Also did an oil change, which hasn't been done in 7 years, and wow! this thing flies! bogs a little in the lower rpms, but when it hits 5k, she screams!
 
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