From what I've written in my posts, it is evident that I am no authority on this subject. The thought that comes to my mind regarding the vertical cylinder, is to wonder if you have changed your TDC as is shown in the video I mentioned. There is (was ?) also a good current thread on this on the other site. There it advises to turn the motor forward in the usual direction of motion, 270 degrees rather than back 90 degrees as the video suggests.