RV Repair: no spark, ground signal, auto mechanic

Question
I am no expert but I tried to start my onan generator it is a bge/nhe I have no spark do I have to drop the generator or is there a way I can find the problem from the top. I have a little room. I changed the plug and did a complete oil change and all then I found I had no spark. this is the first time I have tried to start it since I bought it. the previous owner said it was running when he went into his house and when he came out it was not running, I need to know if the coil could go bad like that and if so is it expensive to change I have problems out here because there is a lot of sneaky generator mechanics and I dont trust them. I also dont have alot of money to spend on it. please tell me what is the first thing I should do to determine the spark status and where should I go from there if the coil is good. like I said I dont have a lot of money so I have to do it myself. I am an auto mechanic so I dont feel I will have to much trouble fixing it I just need to know what is my first step. thanks

Answer
Hi Steven:
Normal checks for no spark. You can do it without dropping the generator. If you have no spark either the 12v dc is missing to the coil, the coil is bad, the wires are bad or the ground signal is missing. Take both wires off the coil, run a hot jumper to the hot side and connect it to DC+. connect a second jumper to the ground side of the coil then touch the other end to ground. When you take the ground wire away you will get one spark, if you do the coil is ok and you either have no hot to the coil or no ground signal. If you get no spark the coil is bad. The hot comes from the generator board and the ground either from a set of points or a magnetic pickup module. To change these the generator has to come out, they are located behind the front engine cover. Good luck.
Bill