I am rebuilding a Hercules Jxld that I got in a box. It is for a Oliver oc-12. The crank and cam gear both have S's and dot's on them. Not sure which to use for timing. If I line up the 2 dots the piston is almost at TDC but no all the way and the valves look like they are in the corect spot. If I line up the 2 S's it is way off. When I line up the dot on one and the S on the other the the piston is at TDC and the and the valves look like they are in the corect spot also.