How do you tell if its your rectifier/regulator or stator? I had a load test performed on my battery the shop said it was good.my battery is at 12.6 sitting,bike on and at an idle it was 12.2, no changes to the voltage at high revs but the bike will die if left on for 20-30 mins
For a simple test, if your not super handy with a multi-meter, the three yellow wires from the stator should EACH push out some amount of AC current. The reg/rec will push DC current to the battery when rev'd. It shouldn't take much, maybe 3,000-3,500 RPMs to push about 13.0 volts of DC back to the battery. This can vary slightly, but it shouldn't ever be higher than 14 volts or can cause an overcharge. Doesn't sound like this is your problem though.
I've had to replace my reg/rec 3 times. I bought the bike with a dead one, and then have replaced it twice. Each time it was sort of like a light switch effect(or binary), in that it either did or it didn't push out voltage. I've heard where people have had one or two stator wires go bad, so it only pushes partial voltage to the stator, which causes the reg/rec to push just a small amount back to the battery, but not enough to keep it charged. I believe these cases to be the exception rather than the norm. In my personal experience, and from talking with some others, it has been the reg/rec and it was just plain dead.
I would suggest starting with the low-hanging fruit first and move up to more difficult testing. If there is a way you can start with a fully charged battery, it helpts to take that out of the equation as well. Set your multi-meter to the 12V battery mode and put each wire on each of the two battery terminals, pos to pos and neg to neg (if you get them backswards you only get a neg sign before the number so it really doesn't matter). Start up the bike and turn the throttle to about 2,500-3,000RPMs. The multimeter should either show 0.00, or it will immediately jump up to close to 12-13 volts. It helps to either have a third arm, or to have someone hold the multi-meter, wires, or crank or something.
My gues it that it will show 0.00 regardless of what RPM you rev to, the stator is probably fine and that you just need a new reg/rec. Stay away from the asian built ones on Ebay, they just don't last. They will work, but can't handle any load for any period of time. A battery that is low or partially drained will cause them to over heat and die. I bought my third and final one here and have been extremely satisfied with it: http://www.regulatorrectifier.com/catalog/
If your reg/rec is dead, then you need to do a double check on each of the 3 yellow wires from the stator just to make sure they are pushing out AC voltage. I'd rather someone else jump in and tell you more details about testing that, because I don't want to tell you wrong. The AC from the stator needs to be handled with more care than the DC from the Reg/rec. I did a quick test initially on mine, but I always knew my problem was the reg/rec so I didn't spend much time testing resistence etc... on the stator. Hope that helps get you going.