I recently put together a 90cc baja atv but it will not start. It looks like the starter motor is not getting enough electricity and it is just humming. The lights get power but the engine does not get enough. I dont like its the cdi box , Im not sure if i need a new battery. But the atv does not even make the cranking noise or electric start noise.

 

measure the voltage of the battery before cranking the starter. then, while cranking the starter, measure the voltage on both sides of the solenoid to see what the voltage is doing there. report back all measurements.