Hopefully others more expert than me will chime in, but I wouldn't ride it as is. Maybe I'm just old and cautious, but I think things like locking up happen for a reason (as opposed to by chance), and it's likely to be a reason that will not just go away (I've tried that approach ) ...which means you're likely to lock up again, and you may not be so fortunate next time avoiding a crash. I would still favor pulling off the pipe to get a good look at the pistons.
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-Jim
'93 MC21