Compression:

After the exhaust valve is on their seat (53° ATDC), the pressure and temperature starts to increase in nearly the similar fashion as in the four-stroke engine. Figure describes the compression in a 2-stroke engine. At 23° BTDC the injector cam starts to lift the injector follower and pushrod. A Fuel injection continues until 6° BTDC (17 total degrees of injection), as described in Figure.

Figure: 2-Stroke Compression           Figure: 2-Stroke Fuel Injection