Trying to adjust primary chain. Could someone tell me the easiest way to rotate sprockets to tightest point on chain. Also does the slack vary that much? Thanks

 

Put the bike into a high gear and either roll it on its wheels, a little at a time, or prop the bike up and turn the rear wheel. Take the plugs out to make life easier. It varies enough for it to be important to do this with care. Difficult to put a number on it without doing mine again!

 

You are over thinking a simple operation. Adjust the primary chain at the top mid-point where there is the most slack. There is tolerance in the chain adjustment spec; get it close and you will be fine