i had an 88 wr500, 2 days before the new owners were picking them up, i decided to run them and make sure everything was o.k. I left the battery terminal a little loose, ski was running, then just quit. cdi was fried. Good chance you cdi is bad, but first i would bypass the stop switch. Check the coils,grounds,ect
also, get a manual and you can test it.
I ended up buying a junk ski and swapped out the cdi
good lick
john