Major update.. the crankshaft drives the gear on the left. The oil pump drives the gear on the right. Instructions (the manual, YouTube videos etc..) simply state that the two gears need to be synchronized where the dot/dimples on each gear meet up as shown in this photo. However the crankshaft and oil pump have moving parts in the crankcase that will 'clash' if they aren't properly synchronized and it's more than just lining up the dots. Before installing the two gears shown in this photo, let the oil pump shaft find it's correct resting spot. whenever you turn it by hand, you'll notice it returns back to it's resting position. The dimple on the gear will be be towards the top. Now you can install the corresponding crankshaft gear with it's dimple also near the top. When the two gears are locked together in place, you can now turn the engine crankshaft by hand without any impedance or strange noises. You may have to count the number of teeth between the dimple and the contact point of the two gears to make sure the same number of teeth on both gears are offset equally. You may need to back off the crankshaft gear once or twice to adjust it so that the two dots come together exactly. This is why the engine did not turn when I followed the instructions and assembled it before.. the parts inside the crank case were not offset properly and were clashing together. I expect to have this engine fully reassembled by the weekend (still working full time here), and will post photos & results. Question for the group is - have you seen this additional guidance anywhere else? Do I need to explain it differently?