How to obtain reverse rotation from Enya Engines Enya .53 4-Cycle Engines: Regular Revolution: Timing Gear Position-At the dead point on the piston Valve Timing Intake side valve: Open 20 degree B.T.D.C. Close 60 degree A.B.D.C. Exhaust side valve: Open 60 degree B.B.D.C. Close 20 degree A.T.D.C. Reverse Revolution: Timing Gear Position Assemble the gears by shifting both intake gear and the exhaust gear 70 degrees (7 cogs) to the right and left from the regular position. Regular Revolution: Timing Gear Position-At the dead point on the piston Valve Timing Intake side valve: Open 20 degree B.T.D.C. Close 60 degree A.B.D.C. Exhaust side valve: Open 60 degree B.B.D.C. Close 20 degree A.T.D.C. Reverse Revolution: Assemble the gears by shifting both intake gear and the exhaust gear 110 degrees (11 cogs) to the right and left from the regular position. Enya R120, GP R120 & R155 4-Cycle Engines: Regular Revolution: Timing Gear Position-At the dead point on the piston Valve Timing Intake side valve: Open 30 degree B.T.D.C. Close 70 degree A.B.D.C. Exhaust side valve: Open 70 degree B.B.D.C. Close 30 degree A.T.D.C. Reverse Revolution: Assemble the gears by shifting both intake gear and the exhaust gear 110 degrees (11 cogs) to the right and left from the regular position.