On 2015-08-20, J Burns wrote:

I agree that a manual shutoff is a good idea.

If so, get a ball-valve petcock.

The British , which used manual petcocks for their motorcycles,
typically made them with 3 positions. On, off, and reserve. Early
Japaneses m/c's used a vacuum actuated petcocks. When the engine was
off, no fuel flowed. These can usually be recognized by the "prime"
position, which bypasses the vacuum operated valve:

https://en.wikipedia.org/wiki/Petcock

nb