Gas tank question

[Scott1976CB750]

Hi Everyone. I am doing a little maintenance on the underside of my 1976 CB 750 gas tank.
There was some surface rust, very minor, that I’m going to mitigate. My plan was to mitigate the rust then prime it and seal it. Is that the best option?
Also, the only hose I had was for the petcock

going to the carburetors, but it looks like I should have a breather hose, see the picture attached. Is that necessary? What kind of hose do I have to use for a breather hose if it is. Thanks!

 

[hinksy]

Is your bike a 76 or 77 ? As I didnt think earlier K`s had fuel overflow drains . Just any fuel safe hose is OK , route it along under the tank and out the back then past the battery to the back wheel area . On the K7-8 they come with a twist lock joiner so you can seperate it when pulling the tank .numbers 28-30 in the pic . Also as you cannot see under the tank , rust kill it , prime it and paint it a matching colour of your choice . It only needs to be good enough to stop the rust and only you will see it

 

[grewth]

Looks like the underside of an F1 tank to me, but I suppose the K7 would look much the same.
The "overflow " pipe serves two purposes.
If you overfill the tank it will drain off the surplus fuel to the ground.
But also if you leave the bike out in the rain, the filler flap has no seal, so any rainwater getting in drains down the pipe.
Block the pipe and you could find the filler cap in a little pool of water waiting to get into the tank

 

[hinksy]

Looks like the underside of an F1 tank to me, but I suppose the K7 would look much the same.
The "overflow " pipe serves two purposes.
If you overfill the tank it will drain off the surplus fuel to the ground.
But also if you leave the bike out in the rain, the filler flap has no seal, so any rainwater getting in drains down the pipe.
Block the pipe and you could find the filler cap in a little pool of water waiting to get into the tank

Of all the years of owning an F series , I had never even thought about draining moisture . Obviously it works because I have ridden in the pissing down rain and had never had to worry about water pooling around the fuel cap , doh !

 

[Scott1976CB750]

Is your bike a 76 or 77 ? As I didnt think earlier K`s had fuel overflow drains . Just any fuel safe hose is OK , route it along under the tank and out the back then past the battery to the back wheel area . On the K7-8 they come with a twist lock joiner so you can seperate it when pulling the tank .numbers 28-30 in the pic . Also as you cannot see under the tank , rust kill it , prime it and paint it a matching colour of your choice . It only needs to be good enough to stop the rust and only you will see it

Thanks! This is titled as a '76 but there could be parts form other years on this bike. I've already dated and used a rust mitigator on the underside, will be priming is soon and maybe find a matching color to the top side of the tank. The breather outlet off the tank was just tapped over...

 

[Loki]

I grit blasted mine with fine ground glass them epoxy primer, high build primer, basecoat and lacquer, came out good and no more rust worries.

Loki

 

[hinksy]

Thanks! This is titled as a '76 but there could be parts form other years on this bike. I've already dated and used a rust mitigator on the underside, will be priming is soon and maybe find a matching color to the top side of the tank. The breather outlet off the tank was just tapped over...

My F2 is also a 76 but 77 year model , it was built 12/76 , do you have a complete pic , that helps a lot