Good afternoon all. It's probably been covered somewhere on here but I can't find it, so beta 300ss with grimeca brakes. Back brake started locking after 10 mins I've greased everything up and changed the pads but the retaining clip is missing ( I'm assuming it should have 1) could this be my problem and where would I get 1 if so I've looked everywhere online and had no joy. Thanks 

What do you mean about the back brake retaining clip?  The pads are held in by a M6 socket head screw and the later Evos had a spring fitted between the pads to just aid keeping them off the disc.. 

Assume you managed to push the pistons back when fitting the new pads, but your problem of the brake locking may be due to over adjustment of the master cylinder brake rod- especially if you had very worn pads before. 

If the rod is screwed up too far into the master cylinder, the piston seals off the reservoir hole so oil cannot top up the system or flow back into the reservoir when the brake pedal is released.  So when heat is generated under braking, the oil expands and as it can't get back to the reservoir, it increases in pressure and applies more brake. Try undoing the lock nut on the brake rod and screwing it down a few turns, which should ease off the pressure - and let us know what you find.  

If you don't have any sort of retainer for the pads, they could be moving or twisting in the caliper and jamming against something.

Maybe so, it frees up again after it's cooled down so who knows