As you know I've been chasing the stalling problem of the little Yamaha ever since I got it running. Today I think I've finally narrowed it down, maybe even solved it. The ignition switch has always been, as my Dad would say, "a little fluky". Unlike every other bike in the garage it doesn't snap into the start position but rather slides over and never has felt completely right. 
One day in the midst of trying to restart it after it stalled on me I twisted the key over and slapped the key down in disgust. It started! I've had a few occasions where it wouldn't start and the same drill seems to get it running. Changing the ignition switch would seem to be an indicated course of action but for one thing, a new one costs $130 without shipping. The bike itself is only worth $600 and I recently went over that with the cost of a Title search plus the initial purchase price. Which leaves me either living with the problem or installing a toggle switch and jumping out the handlebar switch. 
It's only gratifying to finally know what I'm dealing with. I've used it to do small grocery runs successfully but with nervous anticipation. Now I can finally ride it without fear of being stuck since I know what to do to rectify the situation. At last. I can use it to ride further than three miles from the house and not fear being stuck.