I am dealing with a similar problem on mine also. On mine once it is warmed up it looses spark. I tested the coil and found that the secondary winding went bad.... just for the sake of elimination test the coil. Do a resistance check between the positive and negative post (with the terminals disconnected) you should get around 0.28-0.38 Ohms. Then test the secondary by probing the negative post and one of the spark plug wires, then test the other plug wire. The secondary winding should test between 4,700 and 7,100 Ohms. I also tested to see if the coil was recieving the signal by puting a test light on the orange wire and kicking it over with the spark plugs removed. The test light will flash if it has power.
Hopefully this helps ya out.