My gas line from pony tank to the on/off valve located next to pony clutch and gear levers leaks and becomes air bound. It consists of about 3" steel line at connections to gas-tank glass bowl and at the on/off valve; the rest is rubber tubing.

My problem is that when I go to auto parts store, they do not have the large compression ring that would fit into the bowl and the valve, for a new line. As I would like to make a new "solid" line from bowl to valve, I don't know how to proceed and I am hoping for advice on this matter. Also the valve leaks, or if I tighten it enough to not leak, then can't turn the valve--needs new O-rings?

You have a couple of options:
Cat still has the large ferrules that silver solder to the ends of the line or change to fittings that use the later style compression fittings. The Cat fittings maintain full 1/4 in. bore diameter, the later compression fittings do not.

As far as the valve goes, there is no "O" rings. They are a double seat valve that seats all the way open or all the way closed. In between you depend on a valve stem packing in the valve stem nut.

The bad news is that Cat has had a run of leakers on new valves. They don't seat right and the packings leak also.

Is there any reason for the fuel line for the pony engine to run over and then back up to the carb? Mine has a fuel shut off at the tank and then another over at the pony clutch side,can I go straight from the sediment bowl to the carb and eliminate all that piping?
Thanks
Don Alves

Seems like you have a mix of old and newer model parts. Only need shut off in one location or the other. The one at the pony side was a convenience thing and the valve block had the fuel filter element in it. No reason you can't go a more direct route so long as you have a filter.

Thanks Old Magnet,I think I will do away with the valve on the left side as it leaks when in the on position.Is the older sediment bowl a good enough filter or do I need an inline unit,thanks again.