[gadavis]

12.18 volts is a very weak battery. A good charge on a 12 Volt battery should show~13 -14.5 volts. The starter generator on these only use 1/2 of the winding to crank with and the other 1/2 do the charging of the battery. So you need a good battery when cranking. I would try a better battery before doing anything else and also check the out put from your generator. Hook a volt meter to the battery and see how much the voltage drops when you try cranking. You need it to stay above 10.5 volts minimum and that will crank it very slow at best.
There should be 13 - 14.5 volts going into the battery from the generator after you crank and speed the engine up. Over 15 volts and you have a bad regulator. You need to hook a volt meter to the battery and read voltage before cranking and then with engine running fast read the voltage. If not reading 13-14.5 volts then it is not charging. Next check the small yellow wire leading from the generator for breaks or what ever. You can momentarily remove the wire then ground the post the small wire hooks to and it should show a full unregulated charge. If it charges when the post is grounded check the ground wire of the voltage regulator or if the wires are all good,then the regulator is probably bad, replace the voltage regulator.