85 Spree Won't Start

[Johnniespeed]

The bottom of the cylinder has a bevel or taper on it, the rings can be held compressed with your fingers and slide the cylinder downward.
BUT ...... there are a couple of things that need to be watched closely, (1) the piston ring gap needs to be exactly over the piston ring stop pin (2) the rings should compress easily and fully into the grooves. ( the Aero 125 has a different top ring from the bottom ring they will not compress if switched )
I always wash and rinse out the oil tank, lines, pump, I use synthetic two stroke oil and spin the pump with a drill to flush and bleed out the lines. ( it pumps real, real slow) I am not fond of mixing the oils, but the labels on the different brands usually say they are safe to mix, but I don't trust that. I happen to use Amsoil Intercepter, but that is simply my preference, I am pretty sure all the modern oils are superior to what was available in 1985.