So you have spark, if you haven't already tried a new plug then do so, have been caught out many times with a plug that was firing but was no good firing under compression.
Once you know you have spark sorted, that only leaves 2 other ingredients required to run, fuel and compression. If you have a can of aerostart/startyabastard or any other brand starting spray, take ofg the aircleaner, hold the throttle wide open and spray right through the carb into the intake for a few seconds, let the throttle drop to about half open and kick her over. If you get atleast a pop or fart or it runs for a few seconds you knowshe does have spark and runs when she gets fuel. Wind up the idle on your carb just in case it is not set high enough to start (easy enough to wind down one you get it running and sort your issues).
Next is compression. Easiest issue and most common are valve clearances. Buy yourself some feeler guages (less than $10, usually less than $5) and check your valve clearances. If they have closed up and need to be re adjusted you could have a valve hanging open and not allowing you to get full compression. Jump on to youtube and google how to set valve clearances. There is a guy called Alex Man who does alot of videos with his honda z50 (same as small bore china motor) who is very thorough and easy to follow. He's good to watch if you want to learn about these engines as he pretty much covers every aspect of the motors in all his vids.
How to Adjust Honda 50/70 cc Valves - YouTube
This is all assuming your kick start is turning the top end over, as the kicker drives through the clutch on small bore motors, if the clutch is slipping/not gripping then your top end wont actually turn over/turn over fast enough, if you kick it over with the plug out you should be able to feel/hear the are rushing out the plug hole making a noise (like a popping noise). You should also be able to feel if the clutch slips when you kick it.
If you do the valves but still have a compression issue then a new bore and piston(new chinese bore and piston is cheaper than getting your existing bore rebored and honed and buying a new piston and rings) is the only real solution, but you should hopefully not need to dig that far into the motor. If it looks like the motor has been opened up before, then the possibilities of your fault are endless, luckily chinese bikes and parts can be had cheap. So far you have only dropped $100 on it. If it were me, I'd grab the son, sit down and watch some youtube vids and make it a father son project to get it running. Not enough kids know how to fix **** in today's throwaway society, and if he's invested in fixing it he's less likely to destroy it knowing it's more fixing for him down the track
