Six Stroke engine, the name itself indicates a cycle of six strokes out of which two are useful power strokes. According to its mechanical design, the six-stroke engine with external and internal combustion and double flow is similar to the actual internal reciprocating combustion engine. However, it differentiates itself entirely, due to its thermodynamic cycle and a modified cylinder head with two supplementary chambers: combustion and an air heating chamber, both independent from the cylinder.

In this the cylinder and the combustion chamber are separated which gives more freedom for design analysis. Several advantages result from this, one very important being the increase in thermal efficiency. It consists of two cycles of operations namely external combustion cycle and internal combustion cycle, each cycle having four events. In addition to the two valves in the four stroke engine two more valves are incorporated which are operated by a piston arrangement.

During the first stroke the inlet valve opens and air-fuel mixture from carburetor is sucked into the cylinder through the inlet manifold.

During the second stroke, piston moves from BDC to TDC, both the inlet valve and exhaust valve are closed and the air-fuel mixture is compressed. The compression ratio of the modified engine is same as that of the original four stroke Honda engine 9:1.

During the third stroke, power is obtained from the engine by igniting the compressed air- fuel mixture using a spark plug . Both valves remain closed. Piston movesfrom TDC to BDC. Third Stroke.

During the fourth stroke, the exhaust valve and the reed valve opens to remove the burned gases from the engine cylinder. Piston moves from BDC to TDC.

During the fifth stroke, the exhaust valve (11) remains open and the reed valve closes. Fresh air from the air filter enters the cylinder through the secondary air induction line provided at the exhaust manifold . The reed valve opens: Fifth Stroke.

During the sixth stroke, the exhaust valve remains open. The air sucked into the cylinder during the fifth stroke is removed to the atmosphere through the exhaust manifold The reed valve opens and the reed valve closes.