Golan Fuel Tap adapted to British Petrol Tank-Prototype

January 22, 2019

Golan Fuel Tap adapted to British Petrol Tank-Prototype

In my experience, it seems all too common to have a discussion regarding efforts to cure leaky fuel taps that are fitted to our British motorcycles. It appears to be particularly true of the large variety of valves originally fitted to 1/4" BSP threaded tanks. I have tried various recommended repairs or replacement valves with mostly less than satisfactory results. In most cases, I have been able to keep the fuel inside the system, but find that one of the taps will leak when the tank is removed from the bike and the valve is off. In other words, it is relying on the float needle to seal while it is on the bike. Leaking oil is one thing, but leaking fuel is dangerous.

1952 Velocette MAC leaky fuel tap

This little project is my attempt to find a long term serviceable solution. I was attracted by the simple design and ease of use of the Pingel petcock (http://www.pingelonline.com/prodcat/fuel-valves.asp). That said, I did not want to see a shiny chrome valve on my 1947 Velocette MSS, so looked for a black version. Luckily, Golan makes just that and so this was the option that I started with (http://www.golanproducts.com/fuel_valves.html).

The challenge in fitting these high quality valves to our beloved British motorcycles is that the Golan filter and feed tube that fits into the tank is about a 1/2" in diameter. This will not fit in the stock British 1/4" BSP female thread tank bung. 1/4" BSP is a British pipe thread that is about 1/2" diameter with 19 threads per inch. You might be wondering why the 1/2" Golan feed tube will not fit in the 1/2" pipe thread:). This is the major diameter of the thread, so the hole is actually less than that.

I wanted to keep the reserve function of the petcock, so I had to do two things:

1. Make an adapter to mate the Golan M22X1 threads to the 1/4" BSP tank bung

2. Make a smaller feed pipe and screen to fit inside of the 1/4" BSP tank bung

To make the adapter, I had to jump through a few hoops since my 1930 Logan lathe is not set up to cut metric threads. But with the right combination of gears, it is possible.

Chucking up and roughing out a stainless steel rod

Cutting the M22X1 threads. I cut with the tooling upside down and moving away from the chuck.

Checking the metric threads with the Golan petcock nut

The next task was to make the 1/4" British Standard Pipe threads. I could have done this on the lathe, but I had the correct die for it. On the lathe, it would have meant reconfiguring the gears and using a 55 degree cutting tool (rather than the more common 60 degrees used on the metric threads).

It took so much force to cut the 1/4" BSP threads (1/2" diameter) that I held
the work in a four-jaw chuck on my rotary table bolted to my mill.

The adapter is taking shape

Boring and parting off the adapter

I added pin wrench holes to the adapter to help install it in the tank

Now that the adapter was made, it was time to modify the Golan petcock to fit through the adapter and tank bung. In other words, the filter mesh and feed straws had to be reduced from about a 1/2" diameter to under 3/8".