I have a 7194, very similar with smaller HP. Same exact problem. Have tried new battery, no fix. I have done circuit check at each of the relay switches and am getting about 10 vdc at the start solenoid. Is that enough to engage the starter relay? I don't know. I may try replacing cables. However, I do like the sound of the added solenoid and may have to try that. Either way, it is annoying as heck, especially when the neighbor needs some tractor work done. She does make some good cookies and lemonade. 
