Hi Shamus,

If the transistor gets hot, I'm not sure it is from to few turns on the coil.

There are two things I would double check. Are the wires wrapped in the correct direction around the coil? Is the power wire going to + on the battery coming off around the right side of the coil towards you? And is the power wire going to the collector on the transistor coming off the coil from around the left side of the coil? And are the magnets for sure North facing out? These can still run even if everything is backwards and if so, it can heat up...I've experimented with that and got a hot transistor. I know this seems so simple that it can never be backwards but sometimes it is the simplest thing.

Have you tried spinning the wheel faster to get more induction to kick it off? Ideally, it will start by barely moving the rotor. If you have a lower resistance resistor at the base like a 10ohm, it will run way easier than a 680 for example but is less efficient but if you want to at least see if it all hooked up properly, drop the resistance and try it out. Lower resistance needs less speed on the rotor to get it going.

If the coil is wrapped correctly as indicated above and you hook it to a battery, the north field should push up on the North magnet facing out on the rotor. Of course you already know this but I'd make sure these 2 things are absolutely correct.

What components are you using? Transistor, resistor, diode? You can see in my picture here of the roller skate motor that I have a 2n3055 transistor and there isn't a 90v neon bulb. You don't really need it I don't think unless you have quite a few more turns.

You can twist the power and trigger wire together before wrapping on coil for a little more efficiency. Not necessary if you just want a simple model to learn from. I wouldn't worry about a diode going to a 2nd battery because you can always add that later. It sounds like you could use more turns. The wire I buy is sometimes on like 10 pound spools of various sizes (and weights)...much cheaper per foot than the radio shack wire. You don't need an external ground.

I hope some of these things help.