If I understood you, you unhooked the battery and ran it after it started and checked the voltage output which was 25+ Volts. If thats the case I can tell you from what Ive seen and read a bikes system changes AC to DC and if it dosent see reference point like a 12V battery it goes all over the place, This was the case on my old kick/electric XL 500. I ran it with no battery for a while and just kick started it, I checked across the leads while running once an saw similar spikes to 50+ volts. I check the grounds and positive leads on my bikes pretty regularly and find them just barely snug sometimes from th heat cycles of crankin. Might keep an eye on this as well as all the ground points on the frame etc.
Reality is merely an illusion, albeit a very persistent one.