I'd start by going though the standard maintenance, cam chain adjust, valve clearance, timing just to rule those out.
My understanding is those pods dont ever go well with those carbs, but if it ran just fine for 60 miles possible something else such as a bad condenser, bad advance springs or coils. I always put in new coils condenser and points on the bikes I pick up just to eliminate them as problems in case something like your problem pops up. So far I've been lucky and havnt had your type of problem yet on the past 15 bikes I've got up and running.
Hopefully someone chimes in thats actually had this happen.