Radials hard to start
It is a long time since I had anything to do with a Radial, however it is not so much a problem starting the engine but rather that they are rotated through several revolutions before introducing ignition to ensure that any remaining oil in the lower cylinders is purged before actually firing up. We used to count off the blades before selecting the ignition switches to ON. The puffs of smoke are simply small pockets of oil getting past the rings while the engine is cold and clearances greater than when normal operating temperature is reached.