Try a 1980-1983 Yamaha XJ650 petcock. Bolts right on. Vacuum operated, but has a "Prime" position which fills the carbs like "real" petcocks used to - you don't have to crank the engine for 30 seconds just to fill the float bowls. Any wonder why EX starters and starter clutches cause so much trouble? The process is similar to "tickling" an Amal carb to fill the bowl. Turn it to prime, put on helmet and gloves and your carbs are full. Flip it to "On" and you're good to go.
The XJ unit has no "Off" position (Prime, On, Reserve), but if it is in good shape the vacuum valve will stop the flow just like it does on the EX. The vacuum port is facing rearward, but you can either flip it 180º or just run a longer hose to the EX vacuum spigot. Your range-to-reserve might be different, due to different tube height, but that can be changed, also.
I finally figured out why I like Ducatis: With their exhaust note and dry clutch, they sound almost like a Guzzi!
Last edited by po18guy; 11-6-2019 at 8:58 PM.