Ok, I've read multiple posts where people have used F3 petcocks on an F2. What I'm wondering is... Is it really as simple as just popping in the new F3 petcock (non vacuum operated) and driving away, or do I then also need the fuel pump to make everything work?

With the vacuum setup, fuel won't flow without vacuum, so if the F3 petcock allows fuel all the time, I am imagining it will be a bad thing. So do you all just turn off the fuel whenever you shut the bike off?

 

what ive gathered from looking it up and searching a bunch of crap all over the internet is its a simple switch you just need to plug the vac line on carburetor #1 that went to the old petcock. After doing this switch, it wont be vac fed but gravity fed however if you leave the petcock on and the gas just keeps flowing after the bikes off, it could possibly lock the motor

 

yup you need to make sure to shut it off. i did this the 1st time

 

Ok thanks. Next quick question. on the bottom of my tank there are two hoses coming out. one is the size of the vacuum line coming from the engine to the petcock (maybe a CH bigger) and the other is a larger, what I guess I would consider overflow line.

Anyone know what the smaller one does and where it goes? I ask because whenever my bike stalls and I open the fuel cap and close it, I can then put the bike on choke and it starts back up instantly. if I don't pop the cap, I can't start it at all. i'm thinking either some vent is blocked that allows air into the tank as fuel flows out, or the petcock is bad. Since it starts when I open the fuel cap, I'm thinking somehow air isn't being allowed back into the tank, and then the fuel won't flow out.

 

The bigger one is a fuel overflow tube while the smaller one is like a tank vacuum line that goes to nothing just kind of hangs there, i took both th lines off because they were dry rotted and one was to small suffocating the tank

 

A tank vacuum line? Is this possibly how air is drawn into the tank as it flows out? If so, I am wondering if that may be my problem. May have to pull the tank and try and run some type of wire through it to make sure the passages are open.

 

Wait what is your problem

 

Make sure the smaller line hangs there, if it is crimped then cuts off airflow. I found out the hardway once heading towards work. Or just remove it, nothing will happen.
F3 petcock is better than the F2. If the F2 vacuum diaphram is busted and you take it apart you will never know(at least mine didn't look it). I changed out mine to a F3 petcock and never looked back(no diaphram).

 

I have completely cleaned the carbs, top to bottom. On occasion i still have a problem where the bike sputters and dies, like it needs fuel. I pull over, open the fuel cap, close it, put the choke on and it starts right up. Every time the bike dies like this, I pop the fuel cap and it starts right back up. I'm thinking that the fuel flow may be slowed if there is a vacuum in the tank and air cannot get back in. So basically I am trying to figure out how that small vent tube on the bottom allows fuel back in. (if it actually does) and how I can make sure everything works like it should.

 

Get a new small intake vacuum line that hangs from the bottom of the tank if you have not replaced the F2 petcock. If you haven't changed the petcock out, then your diaphram in your F2 petcock is not getting vacuum from top of the cylinder head.