It’s automatic, belt driven, goes same speed no matter what I do, even adding some choke. But the belt switch doesn’t work, using an ohm meter no reading on or off… so it must be in constant limp mode?

You have to be careful swapping jets. Not all jets use the same threads or size classification. Not all cheap jets are accurate. at all. Even if the old jets do fit a new aftermarket carb, the idle mixture screw may not.. It may have different threads, or have a different tapered or diameter pin on it's end. If you do buy a cheap aftermarket carb it will always run better if it's tuned to suit your bike and climate, fuel, altitude etc. The trouble is that if you want to buy different jets, or slide needle, you can never be sure the jets are the thread you need, or are going to be that 5 up from the jet you are holding in your hand.

If it's a two wheeler, teach them how to fall off it, without getting hurt. They are going to fall off and most injuries are from still being attached to the bike at the point of impact. They need to practice falling off till their actions are reflex. It's easy to do and it lasts a lifetime. Start by making them lay it down while braking with the rear brake. Find some bit of mud or wet grass and make them speed along to some line then jamb the rear brake hard on.. make it a competition to do the longest skid to start with and they will practicing it for hours. They'll start laying the bike down on it's side and that teaches them to pull their leg out from under it so they can roll away. Make them practice skidding the bike to a stop on it's slide. Do it from higher and higher speeds. Train it as a reflex. When they always pull their leg up out of harms way, when it's a reflex to them, then find some flat grass or mud and hose it down and teach them to do donuts, going round and around with one foot on the ground and the bike leaned way over. They love that. They'll soon be doing it with both feet on the pegs(especially when they see Dad can't do it). That teaches them all about traction and grip and balance and throttle control. Once they can do that, you can introduce a higher speed loop they can hoon around sliding out and getting the front wheel crossed up on. Get them good and used to laying the bike down, and getting their leg out from under the bike. That's the most dangerous thing.. people that don't thin of pulling their leg out, don't think of rolling off backwards or sliding it to a near stop then jumping before the big crash either.. haha.. People that do have their leg pulled up, can do either. Teach them to have fun, to drop their bike, to get a few scrapes.. But teach them their bodies are more important than any bike and too be ready to jump off when needed.

There's little or no satisfaction in doing what's easy. There's always satisfaction after overcoming difficulties.

I know that feel , a feeling of accomplishment when you have worked so hard on something and get it going, after years of doing this I still get it. Good luck!