|A fully functional stable!|
The one thing I changed prior to it dying entirely was the spark plug. The only NGK I could find was a BPR6HS, the bike is supposed to take a BP6HS. The difference is a resistor which prevents feedback to electronic equipment in the system (important if you've got a machine that uses computers and other finicky components - the PW80 is nothing like that complicated).
I'd read that the resistor doesn't matter, but after swapping back to the old plug the bike fired up immediately. I've got to look further into resistor effects on simple two stroke machines like the PW80, but the troubleshooting still stands: when you change something and it suddenly stops working, change it back even if you think it's supposed to be an improvement!
I'm going to regap and try the newer plug again, but if it kills it again I'll have to accept that the PW80 doesn't like (and doesn't need) a plug with a resistor in it.
After it was up and running we had a throttle lesson, walking next to the bike while my son got a feel for rolling on the throttle gently. I then tore around in circles on it - it's a zippy little machine!