Topic: Vacuum Line????

[Wayne Meuir]

On the left side of the #2 Carb on my 78 F3, there are spigots for two lines, both pointing straight up.  The one closest to the air box is the fuel line from the petcock.  The other one was disconnected when I bought the bike.  I assume it is either a vacuum line, or simply a vent to atmospheric pressure but not sure.  The top end was not connected to anything and the end of the line is not stretched as it would be if it were connected.  There is short piece of rubber hose at the carb, then a plastic connector, check valve or something then a longer piece of hose at the top with a small clamp bracket to bolt it up to something.

Can someone tell me what this is and where it goes?

One more question while I am at it.  The shop manual shows two  cylinder head vents going into some kind of contraption under the battery box called a breather separator.  Does this thing require any maintainence other that draining?


Wayne

[joeb]

one is for fuel and the other is to vent, and no just drain.   

[333]

It has been a few years since I had a 750, but I seem to remember another thread that said that both were vents.

[Wayne Meuir]

Thanks, guy.  big help.  I am mostly a two stroke guy and none of my other bikes have all this stuff on them.

Wayne

[Gordon]

If, like you said, one of these lines connects at a point closer to the air box than the other, then they're not both fuel lines.  The fuel delivery hose connects at a level just above the top of the float bowl.  The vent lines connect on another metal tube farther forward and above the level of the fuel delivery hose. 

[Wayne Meuir]

Yea, I already know which one was the fuel line inlet.  I just did not know what the other one was for.  Now I know it is simply a vent.

Wayne

[Gordon]

Sorry.  I meant to say "they're not both vent lines". 

On earlier models they just ran down in front of the swing arm where the bowl overflows go, but yours may be intended to connect to the air box somewhere (for environmental reasons). 

[TwoTired]

On the left side of the #2 Carb on my 78 F3, there are spigots for two lines, both pointing straight up.  The one closest to the air box is the fuel line from the petcock.  The other one was disconnected when I bought the bike.  I assume it is either a vacuum line, or simply a vent to atmospheric pressure but not sure. 

The smaller nipple is for a carb vent hose.

There is short piece of rubber hose at the carb, then a plastic connector, check valve or something then a longer piece of hose at the top with a small clamp bracket to bolt it up to something.

Can someone tell me what this is and where it goes?

The gas tank "well" under the door has a drain hose.  It's a two piece hose with a connector located between tank and seat.  The connector allows tank removal without removing the entire hose.

One more question while I am at it.  The shop manual shows two  cylinder head vents going into some kind of contraption under the battery box called a breather separator.  Does this thing require any maintainence other that draining?

Yes. It has an element that needs cleaning every 3000 miles, per Honda owner's manual.

Cheers,

[Wayne Meuir]

Thanks, gents.

Wayne