eratic boyer?

I am thinking the boyer ignition is causing my 850 to run roughly at about2500-3000rpm.I changed carb settings,single 34 mikuni,rich to lean in the slide/needle area, although it changed the way the bike run it always had a surge on low load throttle settings. When I set the ignition I noticed that the timing wasnt very steady about that speed. Turning the lights on doesnt make it any worse,so battery voltage must be reasonable.Cam chain couldnt be that stuffed could it?. Any body got any suggestions. Have fitted amal spring inside mikuni spring and the carb seems to have stopped sticking.

Cam chain couldnt be that stuffed could it?. Yes it can be and a new one will initially have a settle in time where it will slacken off and need retensioning, you could just have a loose but not worn cam chain.