another vote for ebay.
being able to view what your buying is better than the description we used to have to rely on.

wow bob , what a palaver .

hi rob, reading your original post you are using old amal carbs you have had cleaned but you still need to physically check the pilot bush isnt blocked. plenty of posts about blocked pilot jets.
if ok cross that one of the list.

some photos would be nice

hi allen
i ve used gpz500 clutch springs in a 3 spring with surprisingly good results as their springs are good quality .
electric start triumphs and nortons used a ballast resister and six volt coils to aid cold morning ignition starts with a lower than 12 volt supply while the starter motor draws most of the amps from the battery at the same time.
i wonder whether any modern kit would run into cold morning non starts draining the battery too quick.

fit the outer cups  all the way home, then see how much of the inside of the steering head casting has to be relieved for the races to make contact with the bearing outer with suitable  clearance. when happy fit inners to yokes.
you probably will need a dremel.

the engine dying issue with electronic ignition is a common symptom of a loose wire, particularly the ignition earth wire which i would check first, 12 volt feed to igniton and pick up wires are all suspects.
any swarth on top of thee piston will most likely pass through the exhaust valve into the exhaust.

i ve read synthetic oil is the best form of oil protection on running surfaces but the customer is always right. in my experience if straight oils do not get hot enough it caN build up sludge in the bottom of the oil tank.