Engine start after winter maintenance of the R-1340-S1H1-G.
550 hp (410 kW), 600 hp (450 kW)

If you listen closely you can here the starter motor continue to increase rpm after the engine catches. When the engine is cold, open the throttle too soon will result in a backfire which is caused by the fuel/air mixture that is still lean due to its inability to properly vaporize at the carb. Leaving the throttle where it is, and keeping it alive with shots of primer (this installation has a solinoid operated primer) will avoid backfiring. Just be patient and wait for it....