Velocette service manual explains the complicated Thruxton starting procedure.
From the so-called “Red Book” Velocette service manual, the following are instructions on how to start a Thruxton.
“Turn on the fuel of both taps, and if the engine is cold, flood the carburetter. Some machines may need a little flooding even when hot to get a ‘first-kick’ start.
Retard the ignition to approximately half the travel of the lever. Depress the kickstart crank until compression is felt. Release the crank and allow it to return to the top. Using the exhaust valve lifter control, press down the kickstart crank slowly to the bottom — no farther. After bringing the kickstart crank back to the top again, the engine is ready to start by using the kickstart without lifting the exhaust valve. One kick should suffice if the throttle has been set correctly.
The throttle valve should not be opened more than approximately 1/16-inch when starting.”
Learn more about the Velocette Thruxton by reading Velocette Thruxton: A Tale of Two Fishtails.