You stated, in a no start condition, the starter clicks and will only start using a jumper battery? This indicates a lack of voltage when cranking either through connection issues which have been addressed by Turbo, Dzhaks and several others or because of a flat battery. Since the bikes starts up with a jumper, we need to know what the battery is at when you have the problem. If the battery is low, I'm guessing the bike is not charging properly and the battery might be getting flat. What's the voltage with engine running? You also stated that you "have a voltage leak" and need to keep it on a tender. That's another indication the battery isn't up to speed, assuming your wire connections are checked and good.
Pure speculation since we don't know what we are starting with... As Turbo stated, you need a voltmeter and we need the numbers....
Also, when you had the starter out, did you inspect the ring gear? How did it look? What about the bendix on the starter? Curious to see if the gears are a bit chewed up which would make starter engagement hard.