I installed a mustang solo with rider backrest. I have not been able to adjust the height of the backrest or pull it out of the seat. CI didn't receive any instructions, can someone share the secret with me?

 

You should be able to just pull it up and out unless its some howstuck? The back of the backrest should have four grooves cut in it to set the height.

 

Mine was stuck to start with, look down into it and put a little liquid wrench on the detent ball and it should slide out with a little tap or two. Not much liquid wrench though a little goes a long way!