1982 honda nighthawk 750 cold starting

[lawnmower man]

i have a 1982 honda cb 750 nighthawk . the problem after sitting for two weeks it takes a long time to start and wears the battery down, its like im losing prime or something? on day one after a good ride it starts right up and day two it takes 1 minute to start , day three , 2 minutes , and so on, after a week it is hard to start. id like to find the problem, can anyone tell me where to start could it be losing its prime or vacuum ?

 

[Travis]

Does that bike a vacuum-operated petcock?

 

[user8086]

Your problem is probably more in your battery do you have a multimeter put it on the battery with a full charge and then start it.. if the voltage drops there is an issue.. when you ride it everyday they probably keep it charged enough to start... That tank if I work all or that bike is just gravity fed petcock I believe.

 

[lawnmower man]

Your problem is probably more in your battery do you have a multimeter put it on the battery with a full charge and then start it.. if the voltage drops there is an issue.. when you ride it everyday they probably keep it charged enough to start... That tank if I work all or that bike is just gravity fed petcock I believe.

brand new battery full charge . petcock is simple but attached to the carb is some kind of a fuel vacuum. ill have to read up on it

 

[Turbobri]

brand new battery full charge . petcock is simple but attached to the carb is some kind of a fuel vacuum. ill have to read up on it

Did you ever figure out what the problem was? I have the exact same issue.

 

[lawnmower man]

Did you ever figure out what the problem was? I have the exact same issue.

no i did not , did you?

 

[Travis]

What positions does the petcock have? If it has a prime position, try putting in on that for about 15 seconds before you start it (when it's been been sitting for a long time).

 

[Tailchaser]

What I do is to put a longer pipe on the vacuum side of the tap and gently suck to open the tap so the carbs can refill and then replace the pipe with the one going to the engine. Couple of turns on the starter and she fires up.

 

[Sixgun89]

Vacuum switch on petcock is not working! Use a fuel line right from the tank to confirm

 

[Sayer308]

I know this is an old post but here's what's going on in case anybody in the future is wondering. The device mounted to the carburetor rack with three ports is a automatic fuel shut off. It uses vacuum to open when the engine is running. When the engine is off the automatic shut off turns off fuel flow. The fuel in the carburetors evaporates when sitting for long periods of time. This is actually a nice feature that they came up with because the carb floats are so notorious for sticking and dumping your fuel out the overflow when parked. What I do for starting my bike after sitting longer than a week is crank for 3 seconds to build vacuum and open the automatic fuel shut off, then wait 15 seconds until the bowls are full, and then start the engine.

One other thing to note if you run wide open throttle for long periods of time, there is very little to no vacuum and it will close the automatic shut off, starving for fuel after a long pull.