Stuck whilst re-assembling

[chickenkiev87]

Hi all, I recently took apart CB750 twin cam 1980 model and left it standing for a few weeks in my garage. When I came back to it, it all went together fine until I got left with what I believe is a breather tube which I am unsure where it goes!

You can see the source of the pipe from the carburettors, can anyone tell me where the other end needs to go because I am completely at a loss as to where it came from!

Thanks in advance

[icerigger]

That's the float bowl vent and, like the green wire, it doesn't go anywhere. Just lay the tag end atop the valve cover.

[LukeM]

A few possibilities:  it's a vent line for the carburetors, a vacuum line for the fuel manifold valve, or a feed line from said manifold valve.  I don't recall the DOHCs having a vent line, but I've been wrong before.

Where does your carburetors' fuel rail get its gas from: directly from the petcock, or though a vacuum valve on the right side of the carb bank?  If directly from the petcock, and the bike runs, then this may have been a leftover from the FM valve.  If it doesn't, then the FM valve may still be in place.  This valve needs a vacuum source to open up, and deliver fuel to the fuel rail. You can bypass this valve if you wish, as long as you're fastidious about turning off the gas at the petcock when you shut down.  You will need to plug that vacuum line to keep your bike running well.

The FSM we have on the home page of our forum for the DOHC bikes should have some more info about this.

Good luck, and hope this helps.
Luke M

[icerigger]

Sorry, meant to say airbox, just lay the tag end on the airbox. I put a bit of nylon mesh over the end to keep out critters and crud.

[Lucky 1]

All carb float bowls need a vent or the engine could not get any fuel.
It is like putting your thumb over a straw.

The straw is the float bowl, when you take your thumb off
of the straw then the fuel will flow out. Get it?

Got to have a vent.

[chickenkiev87]

Thank you all for your help, much appreciated!