1998 AC 500
Mikuni carb
I am missing the screw from down by the overflow. Does the screw for that stop the drain?
If so I think it needs a special screw. Am I correct? Seems to me that without it the bowl can't fill. I can block off the screw hole but the overflow tube is still open. Is it worth getting the correct screw ?

 

Yes get the correct screw.Item#30.CountryCat.com It serves as the bowl drain screw,but if fuel level gets above the the bowl overflow tube,still allows fuel to bypass the screw and out the overflow channel. May be time to order a new needle and seat also if you get the screw as it may be worn/float level off,etc.Or may be cheaper just to get the carb kit.http://www.ebay.com/itm/like/381642899583?lpid=82&chn=ps&ul_noapp=true

 

Should there be a tube inside the bowl (overflow tube)? As it is right now absolutely any fuel that enters the bowl will drain out.

I will get that screw.

 

I know about the exterior overflow tube but what stops the gas from draining out of it? Since its at the bottom of the bowl where the gas sits. I have looked at the diagrams and see no such device.

 

Most carbs either have an over flow tube where gas can go straight out of the carb if fuel level gets too high or they can have a small opening close to the top of the bowl that channels the fuel to the overflow. The drain screw is primarily that,loosen it and all the fuel in the bowl will drain. See if this picture helps.

 

Ok. So the screw which I am missing will block off that drain. If I need to drain then just loosen the screw.
The pic helped and gave me an idea.

Thank you tech. Fantastic as always.

 

Here's another pic with the over flow tube. Green arrow points to where the drain screw threads shuts off fuel flow from the bowl. Yellow arrow points to the over flow tube that has a direct channel out of the bowl if it gets too high.

 

I don't have the tube the yellow arrow points to. Just the port the green arrow points to.

 

I will have to check if there is a Channel under the point that tube would go in. If not I guess it won't have one.

 

Like I mentioned if you don't have the tube you have another port in the bowl somewhere for the over flow channel..