Lost screw to 1982 maxim Petcock. What Size?

New to the forum. Thought it was a good idea to join(just in case I have more problems). Just got a 1982 Maxim 750 for one hell of a deal.
Now the problem:
I was riding to day and must have hit a bump and now I have a gas soaked leg. It turns out I lost the screw that goes below the petcock valve. So here's the question what size is the screw and what does it do?

 

Are you talking about a screw IN the petcock valve, or the one attached to the clamp that holds the fuel line onto the petcock valve? Do you have a picture of the missing screw?

IF it is a screw in the petcock valve, they tend to be the same bolts throughout. If it is in the face of the petcock (the part with the knob to change from ON to PRIME to RES) then those four screws are the same thread pitch and size. Take another out, go to your local hardware store and get a replcement.

IF you are talking about the two bolts that hold the petcock to the fuel tank, those are also the same thread. Same rule applies.. take the other out, go to the local hardware store and buy a matching bolt.

IF you are talking about the bolt that holds the fuel line running to the carbs onto the petcock valve, that is a simple hose clamp. (You guessed it), take the the clamp off, head to your local hardware store and get a replcement clamp.

I would recommend a dab of threadlock and a check of the torque on the rest of the bolts to assure you don't lose any additional hardware with the exception of the hose clamp for the fuel line - this does not need threadlock.

 

Here's a pic. It is the hole under the selector. The old one was a Philips head.

 

Check with chacal our on site vendor. I'm sure he can tell you what size you need.