Did you change the brushes? If you did, are they good 'uns or do they write like an HB pencil? If they do, bin them soonest and get some better ones not off ebay probably. And clean the slipring to get the black smears of soft carbon compeletely off it. Dust from soft ones will stick to the slipring and track all round it, making the firing behaviour very weird.
If the condenser does need changing, then the 'snip' thing isn't that hard. You just need to identify and snip the live wire off the coil to the condenser.
If you have the armature in front of you, with the cb end away from you and the 'nose' of the slipring that goes through the hole in the brass uppermost, then the live wire is at 'lower right', drive end, behind the brass bit nearest to you.
That wire has two strands in the one insulating sheath. They need to stay connected to each other, but NOT connected to the condenser. That way, the live feed from the coil goes along the coil to the contact breaker end via the second strand, but NOT via the condenser. The two strands are often soldered up nicely and all you have to do is insulate the snipped end to ensure no bare bits can get to anything metallic. If the strands end up separated post-snip, just solder then carefully together and insulate.
The other little wire, same end, diagonally 'uppermost' if you hold the thing as above, is the earth. That earths the HT and low tension in one go, and also the old condenser, which is now out of circuit because you've snipped the wire off the other side of it. So leave it untouched.
Brass is C01, steel is C04, yup.
An ATD fault could cause grief if the unit isn't moving off full retard, it's possible. But sloppy indicates a tendency to advance early and probably stay there, so I'd say 'unlikely' to be causing fireworks, more likely lumpiness at tickover and very low revs. The hot starting hassle is most likely condenser, if it's not a fouled up slipring & brushes syndrome.
Worst case, you've got coil trouble. Worth just checking for HT continuity from the brass bits of the slipring with pick-ups off, to mag body. You want to see a few thousand ohms, 5000 would be typical, but continuity is only part of th battle, as the insulation may break down hot, or various other things conspire to spoil your day. If you see Mega ohms, Infinite / Open Line then there's a break in it or it's not connected to the slipring probably.
If the mag is original and the coil doubtful, you'll be in for the full monty to be honest, and it would be false economy not to replace anything that isn't in great shape, bearings included. Doing it once properly beats piecemeal every time, and is better for the blood pressure!
