I'm just doing a service on my Sportster 12C so just a point that might help others doing their own servicing.
This vid covers the clutch adjustment well and it does tell you how to adjust the primary chain.
However, what it doesn't tell you is how to check, properly, whether the primary chain needs adjusted or not - and neither does the FSM as far as I can see. If I've missed it in a search on here, apologies.
Apparently, you should check for the tightest point in the chain and adjust it at that point.
Now, if you're mechanically challenged (like me!) it takes a while to figure out how to move that chain around to find the tight spots. I think it would have been helpful if the vid had explained how to move the chain round to enable this check to be done...
1 get the back wheel up
2 get the bike in 5th gear
3 force the wheel round so it turns the sprockets & chain
4 remove the spark plugs to make it easier
5 test the chain tension at regular intervals as sprockets rotate
6 When you've found the tightest point, adjust it in the manner described in the manual
Alternatively, some say start the bike and let them sprockets spin (although some Trans oil will be thrown out through the inspection cover while doing this). Personally,I can't see how this method would allow you to identify the optimum point for adjustment so it's not for me.
Maybe someone here will tell me I'm overthinking this but if I am, I'd be delighted to find an easier way:s