Motorcycle Repair: xr 75 coil test, volt light, kill switch

Question
my nephew has a xr 75 (78/79 I think. Label is gone) and he suddenly lost spark. my first instinct was to replace the spark plug which I did, but still nothing. Then I bypassed the kill switch but still nothing. I am suspecting the coil but don't know how to test it. I did some research but only found specs for cars. I have tested the lead coming out of the generator and get a spike to about 16volts when I kick it over, which I figure should be enough to work with but I am not sure. I have checked the ground and cleaned it up even though it looked good. your help would be greatly appreciated, my nephew is dying to ride again. Thank you, Dan

Answer
If you have voltage to the coil, the only two things that can keep it from firing are the grounding circuit through the points and a bad coil.  There's no 100% coil test that can be done at home without a coil tester.  So if you check the points and they are making and breaking the circuit, it's probably the coil.  I use a 12 volt light and a battery in series with the points to check the point circuit.  You can't use a VOM because the capacitor will provide a path to ground and it's hard to tell if the points are opening and closing correctly.

Regards
Rich