I know this topic comes up once and a while, and I thought I had this in hand, but I ran into trouble taking apart one of my 1990s-era Riv 4-6-2 streamlined pacifics yesterday. This would be a version with tender pickups and the motor w/ flywheel hidden in the boiler (as opposed to visible in the cab). I don't know if it's a square or round motor.
According to the exploded diagram I have, the body shell should come off by undoing one screw underneath the steam chest, and two screws back by the ash pan (one on each side). When I do this, the front of the boiler shell comes loose, but something is holding the back of the shell to the frame still, in the area right where the motor itself is. I don't see any other screws to remove, and I couldn't get it loose with as much pulling/twisting/bending as I was willing to try for fear of breaking something. The included diagram shares no more details beyond the 3 screws to remove.
I know a number of people have taken these apart to re-motor them or install DCC; I'm just hoping to lubricate mine as it's not a very smooth or quiet runner as it stands (sat in storage for 15+ years). Can anyone share the "trick" to opening up one of these?