If none of that works and you are still using the old points and coil try replacing the condenser and points and if that does not work and you cant find any reasonable solution use a second condenser to build up more spark until you figured it out... sadly that what i am doing right now and i replaced my points, condenser, spark plugs and wires and used 4 coils... none of it fixed it but it runs fine with a second one... heck im not mechanic but it works... =-(.. i used to have the same problem it would run for 15-20 min then die out and the coil was really hot... i got a spark but for some reason it never could run right... so i rigged it, lol prob not the best idea but i hope it can help...