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Discussion Starter #1
My 1980 CX500C has been losing power while running, apparently not getting enough gas. Choking it helps somewhat at that point. When I pull over, open the gas cap, replace it and set back out, it runs with full power again for a while before the problem recurs. I have checked the gas cap vent - air blows through it freely. So I replaced the cap's O-ring, believing it was maybe falling too low on the tank fitting, blocking the vent. But that didn't solve the problem. Has any one experienced this? Or otherwise have any insights?
 

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Did this just recently start showing itself? Any work done prior to this? It's possible that you have a clogged carb jet.
 

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Discussion Starter #6
Thanks everyone. I didn't get any notifications of comments and just found them now. My petcock does not have a vacuum line connection. AND I think the problem is solved and it was something completely unrelated - not sure why opening the cap solved it. The air intake was pointing straight forward instead of at the angle it is supposed to be at. I am not sure if that resulted in too much air or not enough but fixing it seems to have solved the problem, at least for now.
 

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FWIW, the fuel delivery system on these bikes is not pressurized. Gravity feed. As long as the tank and fuel level is above the carbs and no blockage then fuel will flow.

You could even have a loop in the fuel line down to the pavement and fuel will flow from the tank to the carbs, assuming the tank is in the normal position.
 

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Yep. And the orientation of the air intake (assuming you mean on the air cleaner housing)(AKA airbox) should make absolutely no difference - many people have replaced the original airbox with pod filters and the fuel still flows from the tank to the carbs.

If opening the cap and replacing it let the fuel flow again the problem has to be the cap vent (fuel can't flow out of the tank unless air can flow in to replace it).

BUT are you sure it was opening & replacing the cap that made it work again? Perhaps it was just sitting for a few seconds with the engine off. If there is a partial blockage in the petcock or fuel line (or if you have an external fuel filter that is not oriented with the outlet lower than the inlet by half an inch or so) it is possible that not enough fuel can flow into the carbs to keep them full while the engine is running but when you shut the engine off for a while the fuel continues to flow and re-fills the carbs.
 
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