Timing an E and R Classic KPN400?

I have the machine detailed above made by Ningbo Kuang PO Sewing Machine Co Ltd. The bobbin holder mechanism is attached to a short rod which has a cog to drive it. This cog should be held by a collar with two small allen screws, to the rod but it has loosened allowing to cog to float and losing the timing I can tighten the allen screws but don't know how the timing should be relative to the needle and bobbin. Can any one help.