I would start with the rectifier. I bought a used one to replace the one with a dead short that was on the bike when I bought it. The used one fixed the short but it still wasn't charging. I wound up buying a used alternator assembly from a fellow member here on the forum and he happened to throw in a couple used rectifiers. Before I'd gotten a chance to replace the stator I decided on a whim to swap rectifiers once more with the best looking one I got from faithbiker to see if it made any difference. To my amazement after riding 120 miles that day the bike still started just fine so I metered the battery when we got back and sure enough the battery still had 12.6V sitting and went up to 14.16 when I revved the bike up over 2500.

So before you spend $150 for a new stator, I'd start with the rectifier. I'm pretty sure my first used one wasn't allowing the necessary electrical flow to the stator to then be ramped up and sent back to the rectifier/regulator and on to the battery.