Boyer ignition question.

The ignition advance on the older Boyer does not matter much as long as it does not change, because normal practice is to jet to suit the timing and compression ratio. It is possible to go in the opposite direction, and get the jetting right with an oxygen probe, then advance the timing with the bike on a dyno to get maximum torque. If I had continued racing the Seeley 850, I would have bought a programmable Boyer, calculated the advance curve, then move the static timing to suit the jetting.
Any bike will kick back, if you are careless with the kick starter - just keep the pressure on it - if it kicks back, it does not matter - just hold it and don't let it bite.