Coolster 125. Starter does not engage when the button is pressed. Checked battery it's good, main fuse is also good. Any thoughts? Starter? Brake depressed but not allowing start?

 

First, wire a test lamp between the live terminal and earth on the starter, if it lights when you press the start button, you have a faulty starter. If it doesn't light, try to feel if the solenoid clicks when you press the starter, if it does, you have a faulty solenoid. If it doesn't, things get more complex as a faulty lockout switch, starter switch, lockout relay (if fitted), or faulty wiring, can all cause problems.