The piston is jammed solid in my latest acquisition, a 1989 Moto Guzzi 500cc Monza.. So far I’ve it soaking in penetrating oil , lightly tapped with a wooden drift and hammer.. absolutely no movement…. Apparently this bike hasn’t run for somewhere between 15 to 20 years…. The engine internals look very good but sadly bone dry.. Any one have any brilliant ideas?
Try going in from the bottom, remove the crank, , do what you have already done, then wait, try twisting the conrod after a couple of weeks (carefully back & forward), the rings are rusted to the bores, by the sounds of it.
Boiling olive oil dumped onto the piston top to heat the piston and tap with wooden drift when cooled.
