1978 fuel line/gas tank

[Sean_melican]

Hello all. I’m new to motorcycling. Just bought a 1978 CB750. It needs a little cosmetic work but seems in good shape. The fuel tank was rusty so I pulled it off to clean out with vinegar. There were two hoses. One connected to the petcock and the other seemingly connected to nothing except the tank. Can someone kindly explain what this is and where to connect it on the engine? Thank you.

 

[grewth]

I can't really make out exactly what model you've got there, but I suspect that pipe is the rainwater drain pipe from the filler cap well.
The SOHC F series all had them so I suspect K7/K8 will be the same

 

[hinksy]

Thats no.29 in the pic , it is the overflow drain hose and when connected , runs down past the rear tank mount over the airbox and down in front of the rear guard and wheel

 

[grewth]

Thats no.29 in the pic , it is the overflow drain hose and when connected , runs down past the rear tank mount over the airbox and down in front of the rear guard and wheel

Hmmmm.
I never thought about over filling the tank.
I don't think I've ever been rich enough to afford that sort of luxury.
If that pipe dumps out in front of the rear wheel, it could be dumping petrol onto the rear tyre as you're riding.

 

[hinksy]

Maybe they thought it would make your tyre extra grippy . Not a fan of the idea myself , but the carb overflows go to the front of the tyre . You can see my hose in it`s mounted position next to the centre stand and it is in it`s original hose clamp

 

[grewth]

1960's and '70's Triumphs had a breather pipe clipped to the rear mudguard.
Apparently this moved the oil leak from in front of the rear wheel, to behind it