http://www.48north.com/mr_offline/atomic.htm

"From what I know about Atomic 4's (A-4) is that if you have the
basics, good spark (ignition), good compression and good clean fuel
the engine should run. These three factors, along with proper
maintenance, will keep the Atomic 4 going as it has for over thirty
years.
The Atomic 4, (also known as the Atomic Bomb or Anemic 4) is a very
reliable engine. There were over 40,000 engines built with
approximately half still out there running today! They are very
simple, grass roots, low tech engines that (like every other engine)
require routine maintenance such as frequent oil changes, tune ups,
clean fuel, visual inspections, and proper cooling systems. "