Walker

I have walker mower with a 25 HP motor that quit running, it cranks over but have no spark, I've checked all safety switches and they are working fine, if I disconnect the ground wire from coils then it will start and run, but the minute I hook the ground back up I have no spark, I'm a my wits end trying to figure this one out,anyone have any idea what I'm missing or need to check?.

You are going to have to go hunting with your eyes and fingers. What are you hunting for? You must trace the kill wire back, looking for either nicked or frayed wire or a pinched wire. Both of these conditions will cause a short, which will kill the engine. This might take five minutes or five hours. Sorry, but I have had this many times and you just have to have patience. A multimeter would come in handy if you have one, it test for shorts. Work back from the coil.