If the solenoid pictured starts the bike fine, then a double-tap will also KILL the bike.
Have you configured the MU in the MENU to use 5 buttons? Are you using an M-Button?
The double-tap needs a clean sequence of pushing the button, twice. Push. Push. Not push-push.
There are other sequences of multi-push that also trigger other functions. Have you tried those too? Do they work?