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Discussion Starter #1
Hi everyone.
I'm new to the forums, but was hoping to get some much needed insight.
My 86 vulcan 750 runs perfectly fine until it uses about 1.6 gallons of gas (gauge at a little more than half). Then it acts like its out of gas. If I flip it to reserve, I can run it down to about 3/8 of a tank. Do I have the wrong pick up tubes on my petcock/tap? That's only explanation I can think of. I have not had the chance to drain the tank and investigate further.
I have also noticed that other people have RES, ON, and PRI on their petcocks, while I have RES, ON, and OFF on mine. Maybe the previous owner put in the wrong part.
It's not a huge problem to get gas every 90 miles, but it would be nice to have some range so I can go on a road trip.
What do all of you think? I appreciate any responses. Thanks!
-Neil
 

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depending on riding style, a tank only lasts 100-120 miles anyway. when switching from main to reserve, its only 0.6 gallons of gas left in the tank before your too low for reserve to pickup fuel

you may have wrong pickups, I dont know if they can be interchanged with pickups from a different petcock.

the 750 had 2 different pickups, depending on year. the difference is the pri position, which is for Prime. it allows fuel to flow to the engine with the engine off. normal operation is a vacuum operated valve (all years) that gets its vacuum from the left side carb. so if the engine isnt running, you may not be able to get fuel to the carbs for starting.

the 2 petcocks are interchangeable, the only difference is the prime position I mentioned above replaces the off position.

you may just have a bad sending unit in the tank, or a bent float rod for the sender assuming the petcock is proper.
 

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If the carbs are starving for fuel with the tank still half full, I suggest you check to make sure the fuel venting system is not clogged. if no air gets in the tank, then a vacuum is created and the fuel flow to the carbs stops.
Search the forums for POOG (phantom out of gas).
A quick opening of the gas cap to let air into the tank and restart should restore fuel flow if the vent line is clogged.
 

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If the carbs are starving for fuel with the tank still half full, I suggest you check to make sure the fuel venting system is not clogged. if no air gets in the tank, then a vacuum is created and the fuel flow to the carbs stops.
Search the forums for POOG (phantom out of gas).
A quick opening of the gas cap to let
air into the tank and restart should restore fuel flow if the vent line is clogged.
Good catch, completely slipped my mind.

Are you still building lights?
 

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Discussion Starter #5
Interesting. The consistency of when it runs out of gas is rather odd to be PROOGS. The temperature doesn't effect it, only the level of fuel in the tank. The gauge seems to be on par with how much fuel is in the tank. I can only ever use 1.6 gallons from full. Then its out of gas and I have to flip to reserve to get to a gas station. Hopefully I'll have a chance to pull the tank this week. I'll double check the vent for the tank.
I'll be sure to post what I find!
Thanks!
-Neil
 

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Might be worth draining the tank at the petcock and see how much comes out between 'on' and 'res', then measure again to see what's left at the end. It does sound like the stems are too tall if there's still gas in the tank when the carbs stop getting fuel.
 
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