Are Rotary Engines Reliable

How long do rotary engines last?

Jean-Pierre Derdeyn at Derwin Performance tells Hagerty that a properly maintained rotary engine could last 50,000 miles or more with no problems if the cylinder head is properly installed.

Why are rotary engines unreliable?

Due to the long and uniquely-shaped combustion chamber, thermal efficiency of the engine was relatively lower compared to piston-cylinder counterparts. This also often led to unburnt fuel leaving the exhaust (hence the tendency of rotary engines to backfire, which is obviously as awesome as it is inefficient).