Depends why it's not working. Most likely, with it being a 125, the exhaust valve is totally gummed up with carbon as the previous owner has never cleaned it.

Trouble is, if that has happened, it has probably burned out the motor, or toasted the control module inside the ignition unit.

You need to get yourself a manual and remove the powervalve to check the state of it...
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball