1985 yfm200
 

I bought my son a 85 YFM200. It sat up for around a year before the guy sold it finally. It has a host of starting issues which I'm stumped on.
1) He had a no start issue and replaced the Rectifier/regulator. It started up fine for a day or so, then it quit. I replaced the starter, starter relay assembly, and coil. I then got it to start by running a push button switch straight to the starter relay. If I use the handlebar switch I can hear the relay and starter solenoid click, but nothing else. If I use the pushbutton wired straight to the solenoid it will turn over. I have power to the solenoid both ways, and the only thing I see that could be different is that is going through the relay to the solenoid I get 10V whereas when going straight to the solenoid from a push button I get 12V. Can 2 volts change it that much?
2) To start the atv you must hook it to a jump box and turn it to 150 amps. I have put three different batteries in it, and even pulled the one out of my street bike and my other atv with no change.
Any ideas on either one of these would be helpful.