carb breather pipes

[Agemax]

what purpose do these actually serve, apart from the obvious? the pipes that come out between the carb bodies, one of which is the vacuum for the fuel tap.
my question is, if you had pods fitted, could these pipes be blocked off or best to leave them open to the atmosphere? will fuel leak from these pipes or are they there purely as a vent, to eliminate an air lock maybe?

[Steve]

One of them is NOT for the petcock. THAT one is on the other side of the carbs, on the outlet tube of either #2 or #3 carb, depending on whether you have BS or VM carbs.

The vent tubes, the Ts between 1&2, then 3&4, are there, as you supect, to prevent air lock in the float bowls. The recommendation that I have seen the most on this board is that if you have the stock airbox, leave the stock vent tubes connected to the Ts. If you are running pods, leave the Ts in place, but remove the hoses. I, for the life of me, can not figure out what difference that makes, but those who have done it say it makes a difference. Whatever you do, don't block them off.

.

[hampshirehog]

Obviously you have to block up the vacuum tube if you're not running a vacuum tap. The other 2 tubes as Steve says are for venting in the carbs. I suppose you should really leave the hoses on as you could in theory get a fuel leak if your bowls overflowed but I've run many a bike with the hoses missing with no problems.

I also remember years ago buying a GS750 (I think - may have been a 550) where the PO had joined both vent tubes together using one hose. I didn't check for ages (too lazy ) and the bike ran fine so I think the vents are of dubious value.

[C.V.]

I also remember years ago buying a GS750 (I think - may have been a 550) where the PO had joined both vent tubes together using one hose. I didn't check for ages (too lazy ) and the bike ran fine so I think the vents are of dubious value.

The po of my '79 850 had vents #2 and 4 connected to eachother as you describe. When I rebuilt, I vented both to air, per stock setup, but cyl 4 didn't fire untill i reconnected the 2 vents.