I've watched every video I can find on the subject and still a little confused.  Prior to this one all of my old Yamaha Enduros had a fixed plate under the flywheel.and the timing was set by when the points open with no regard to point gap (which I always thought was odd since it's so critical on my old cars).  This one has an adjustable plate, so it seems like it would make sense to optimize the points gap and then set the timing by adjusting the plate.  So............. WHAT IS the optimum point gap and exactly where in thousandths (I don't have a metric dial indicator) BTDC should the points be opening?

15 thou max & think the 250 is 3.2mm so128 thou . Someone will correct me. One thing to be a bit careful of is sometimes the points seem to get wider late in the lift before closing. Not sure if its cam wear or even slight crank out of alignment. But i used to go--starting to open--then around a bit to where the limit is for getting at them through the slot & call that max lift. But--in your case i'd leave the plate where its always been looking at original screw marks & set the piston at 128 then loosen points screw & have them touching but parting [on the point of] & then see what gap comes up at max open. Anywhere between 12+ to 15 is ok. Sorry--got carried away there--or should be lol!!.
Also, you'll find that tightening the points screw & the damn things alter slightly so trial & error till ya get it right. & to really confuse things you could mark 128 then strobe it but they likely will not show what you set it at even though it should.Should be close but possibly very slight main bearing wear or just vibration & it'll move around, Can't beat CDI even though i was bought up in a points world & my old 250 & 360 both have points. Made up a simple CDI system for another 360 motor i've shelved at the mo but ran normal. Used a DT360A plate & stator coil & one wire to an RG50 plug coil box combined & she works.

Thank you.