04-22-2017, 03:31 AM
The 750cc BSA Rocket triples were a lot less lumpy than the 650cc BSA Lightning twins.
The offset smaller pistons in the Rocket 3 allowed the crankshaft to turn far more smoothly. The larger pistons in the Lightning both rose and fell at the same time. They had a huge flywheel in order to provide enough inertia to keep the pistons in motion.
Slinging all that weight around was the reason BSAs twins were called Birmingham Vibrators. However that lumpy engine, lots of torque, and that beautiful exhaust sound were the things that endeared me to my Lightnings.
My first Lightning bathed the greasy side down with oil because of a built in chain oiler. When I rebuilt the motor, I found a small pocket inside the primary chaincase cover. It gathered oil when the triple link primary chain was in motion. The oil would pass down through a channel to a short rubber hose over the drive chain. I dropped some solder in the hole in the bottom of the pocket. No more oil leak. Drive chains were lubed by boiling them in the motor oil removed during an oil change, which were far more frequent then.
The offset smaller pistons in the Rocket 3 allowed the crankshaft to turn far more smoothly. The larger pistons in the Lightning both rose and fell at the same time. They had a huge flywheel in order to provide enough inertia to keep the pistons in motion.
Slinging all that weight around was the reason BSAs twins were called Birmingham Vibrators. However that lumpy engine, lots of torque, and that beautiful exhaust sound were the things that endeared me to my Lightnings.
My first Lightning bathed the greasy side down with oil because of a built in chain oiler. When I rebuilt the motor, I found a small pocket inside the primary chaincase cover. It gathered oil when the triple link primary chain was in motion. The oil would pass down through a channel to a short rubber hose over the drive chain. I dropped some solder in the hole in the bottom of the pocket. No more oil leak. Drive chains were lubed by boiling them in the motor oil removed during an oil change, which were far more frequent then.