Need some basics

Tnc TNC Scooters (Scooter Sales and Service) can set you up with a controller and throttle. At the risk of preaching to the choir... the controller to match you motor and voltage is what you need. It will come with a circuit for a throttle. If yours is three wire you might be able to reuse it. It will also have a lock circuit and some other stuff you might be able to use. I don't know what your watt motor is but I was looking for a 24volt 500 watt and I think it was 20 bucks plus shipping. Also the throttle is about ten bucks if yours won't work.

Good luck...

To be honest at that size there are some really inexpensive ones on ebay now and then. I would check TNC first for a comparative price. I buy a lot from them and their stuff is all good. But I bought one from hong kong that seems to be okay as well. I only use the battery, motor and derailer circuits I tape the lock wires together. Actually I have lately begun to not even use them. For a 250 watt motor I would just go buy me a switch at the hardware store. You have everything you really need.

Pedal it a couple of times before you turn it on. Then it will just go wide open. At 250 watts you will want to run it wide open anyway. If it's a standard mount motor you might want to replace it with a high watt one. Of course then your battery consumption will go up.

your controller is the on off switch... You just run it like a pulse jet.

Good luck...

Ps if the electronics are fried, First thing I would do is to find the motor wires. Then it would test it with the new battery pack. Odds are petty good that the motor isn't cooked just the controller. If it is a 400 watt you might want to buy a controller since with a singer circuit on one so strong it will probably throw off the chain if you hit it with full throttle. Now I use an on off on switch and run one leg at 12v and one at 24 volts I start at 12v and then kick it up to 24
but then I'm a junk yard dog type builder