Topic: Newbie Questions re CB650 Fuel Valve

[JaySing]

Hi, I have some basic questions regarding the fuel valve on the CB650 I'm trying to get running.  I'd really appreciate any help you guys could give.



1. How do I connect from the fuel valve [7] to the petcock?  I was looking at 4into1 and they were selling a black opaque fuel line with the same dimensions but do I connect that to the existing fuel line?  I've attached a pic of current fuel line below.



2.  Where does the air vent tube [5] connect to? 

3.  Does the vacuum tube [4] use vacuum pressure to pull fuel from the tank?  Does that mean it only pulls fuel during cylinder 2's intake stroke?

Sorry if these questions seems basic, I'm still relatively new to this.

[kerryb]

I'll get you started...
The vaccuum is used the open a diaphragm valve that lets fuel flow only when the engine is running.  This is nice because you don't "have"  to worry about shutting off the petcock, it is automatic.
The vent tube is just that, a vent to atmosphere.
If your diaphragm is working properly, you can suck on the vaccuum line and allow fuel to flow from the tank through the valve and on to the carbs. 

Many users will eliminate this vaccuum valve in favor of a simple petcock on the tank feeding the carbs directly.
Hope this helps.

[JaySing]

Thanks for taking the type to reply.  If I'm starting the bike after a long time, e.g. a couple years, should I actually suck on the vacuum line to fill the fuel line with gas or do you think the starter motor will create enough vacuum?

[scottly]

If the petcock has a "P" (prime) position, it will allow fuel to flow without vacuum. If it doesn't, it's easier to just suck on the line to fill up the float bowls. The battery on my FT would be dead by the time enough fuel would flow to start the motor...

[JaySing]

Thanks for the advice, guess I'll have to suck the vacuum line to get fuel into the carbs.  Any advice on how to connect the fuel line to the petcock?  Am I supposed to add another fuel line to bridge the distance to the petcock or just replace it with a longer fuel line?