On a Norton 16H, there is 15 - 20 miles on the unused side of the fuel tank, depending on how much has been sloshed around.

The only BSA, as far as I'm aware that has to be ridden with both taps open for high-speed runs is the 750 Rocket 3 (along with the Triumph Trident), they can run lean and home pistons due to the restriction of a single tap..But they drop to about 20 mpg ridden hard.

The Ariel W/NG is another such bike with only one tap and balance pipe.:rage: Ron

email (option): ronpier@talk21.com

All I can add is that my M20 with two plain taps will get you from Aylsham to Swanton Morley, about 15 miles , on a very dark night on reserve. I'm pleased to say
Richard

So 2 main taps is the way to go? (No reserve tap) , just to finish off what’s the thread size required? My 2 taps leak like a sieve!

email (option): neil.blount@hotmail.co.uk

Originally the taps on a WM20 were 1/8 BSP both ends, But lots have been changed now to the more common 1/4 BSP. Ron

email (option): ronpier@talk21.com

I have got so fed up with leaky original tasp that I have changed ovefr to Bap taps on all my bikes. I get them in pairs (maoin and reserve). Admittedly a bit more fiddly to operate on the M20 due to the carb cables being right in front of them but a price worth paying for long term reliable taps.

Ditto...BAP taps are inexpensive and effective..I've used them for years. No good for rivet counters of course....:relaxed: ...Ian

email (option): ian@wright52.plus.com