I am placing rear brakes on my 2009 trike. I have tried to compress the piston on the left side caliper, the one with the parking brake attached. I can compress the piston but not all of the way in order to replace the brake pads. The piston acts as if there is pressure still on it someplace. Is there something I should do to relieve the pressure or do something to the parking brake. Any suggestions would be appreciated.

 

You need to back off the adjuster for your hand brake. At the calipers. Then re-adjust !
You need to get a shop manual, along with the Trike supplement. They are valuable books if you are going to do even maintenance on your bike ! Best money you can invest !!
The Wiz may have the whole thing on here somewhere. Do a search.