I'm rebuilding the engine on my son's Eton Impuls 50. The engine looks identical and shares a lot of parts with the Polaris 50cc so I'm guessing my question would pertain to either.

The little dowel pin that goes into the crankshaft on the MAG side to drive the oil pump gear slid right out of the old crankshaft but does not slide into the new one. The holes on the crankshafts are slightly different diameters. I'm not sure which is correct. Should this dowel pin need to be pressed in? If it does, how should I go about doing that considering there's not really any room to get proper tools in there?

Thanks in advance to anyone that can help. I'm almost ready to put this engine back in and this is the last thing holding me up. My kid is getting anxious!