I am trying to rebuild an 81 rm125 and I have gotten as far as cracking the cases and puting in new seals and checking the bearings. I also installed different trans gears from another motor. I want to check to see if the magneto is still good. When I orginally pulled off the cover the rotor and the metal part of the magneto was rusty. I am assuming that water got in there to cause the rust at some point as the bike had been sitting for a long time. My friend told me to hook it up to a power souce to see if it could run a current through it and test it with a test light. It didn't pass that test but I don't know if that is the right way to test it. I do have the manual for this bike but I am a little mechanically challenged. So if someone could help me out that would be great. I am using this bike as an intro to 2-stroke repair as I will have to do alot of work to get it going by spring. Thanks