Motorcycle Repair: Honda 1981 CM400 Front Brakes, ring groove, putty knife

Question
Brakes seizing. Rebuilt caliper and master cylinder. Can't find relief port in master cylinder for fluid return as I suspect fluid is not returning. Open bleeder at caliper and calipers will disengage. Does this master cylinder have a return port?

Answer
Nope, I'm guessing there's varnish in the caliper o-ring groove preventing the piston from returning.  You have to take the caliper apart and scrape the varnish from under the o-ring.  I use a bent nail that I flatten the end on to act like a tiny putty knife and run it around in the groove.  Just be careful not to damage the aluminum or you'll have leaks.  

Regards
Rich