I bought this to demostrate the Atkinson cycle (unequal intake and power strokes) but this isn't an Atkinson. It is a symmetric opposed piston engine. It is very well made and starts easily and runs great. After a little tuning it is easy to hand start without a drill. It should be noted that the mixture needle is very sensitive with the running range only being about 1/10 turn so adjust in very small increments. The brass parts polish up very nice if you take the time. Just polishing the flywheels makes a great improvement to how it looks. I would have given 5 stars if it was true Atkinson. I may make a single throw crank and Atkinson linkage for it and see how it runs!