So that we are talking the same language, by magneto, you mean the magneto coil and not the magneto rotor? If you removed the magneto rotor, did you put it in correctly?
Is your engine a new install or have you been riding the bike? If you been riding in the rain or left it in the rain, the magneto coil maybe ruined.
As Jaguar stated, the kill switch may be the problem. Remove it from the circuit and try starting. Sometimes you can push it while attempting to start the engine and it will sometimes unstuck its self. I had an 48cc kill switch that would stick all the time, so I would kill the engine by popping the clutch.
Here's how to check the ohms reading on the magneto coil:
Set your meter to 200k:
1. Should get 2 ohms between black and white wire.
2. Should get 300 - 400 ohms on the blue and white wire.
3. You should be getting 300 to 350 Ohms with the the blue and black wires.
Here's how to check the CDI:
Put your Ohms at 200K scale.
1. Positive lead on Blue wire and negative on black wire should be infinite (no activity).
2. Positive on black wire and negative on blue wire should be 130 - 150 ohms.
3. Positive lead on spark plug wire and negative on blue wire should be about 135 - 155 ohms.
Switch scale to 20k to check spark plug wire with black lead should be about 2.5 - 2.7k ohms.
All are approximations for ranges.
Also, make sure your plug is grounded against the engine when checking for spark. If not, you may damage the CDI.
Go over your connections and make sure they are connected. I once had either the blue or black wire not fully connected, even though it appeared connected. Also, check to make sure the spark plug wire is secured to the CDI.
I am not trying to be condescending, but don't know what skills you have and you've left out information that will help us solve your problem.
Good Luck,
Chris
AKA: BigBlue
