I’m going to try and refresh my pre-09 Leopard’s piston/ring myself, with the help of my (former) 4-cycle engine builder, who has a ton of machinery but has never worked on a 2-cycle engine before. He lives 20 minutes from me, which is a huge advantage over shipping out an engine for refreshing, so if we can do this well, it will make my life a lot easier, besides being cost effective.
We’re doing just the top end first. We’ll try the bottom end next time.
We took a look at the engine last night, and read the Parilla repair manual.
– What stone grit should we use on the cylinder walls? Any finish pattern? Or brush to follow up with to remove burrs?
– What is the clearance to use between the cylinder wall and the piston, so we can order the right piston and ring kit.
– How does one order the right diameter piston pin?
– Does one need the fancy IAME tool to remove the piston pin circlip?
– Besides ordering all the gaskets to try out, how does one figure out the thickness of the gasket that needs to be used to get the right engine squish? 0.9mm?
– What other parts should be replaced at the same time? Rubber o-rings?
– I have 2 cylinder heads. What will be faster – the smaller diameter, less used one, or the larger diameter cylinder?
Follow up: I got an AMMCO portable hone, and used the 220 grit. Under the supervision of my 4-cycle engine guy (John Kurtzman of Kurtzman Racing Engines), did a very careful hone, getting rid of some depressed spots, and measured about 20 times, resulting in a 54.20R piston size, up from a 54.15.
Reused the old gaskets (since I accidentally ordered MY09 gaskets), and checked the squish – over 1mm, so plenty safe – and very carefully broke it in over a practice day. The engine rocks! My son took pole, and led every lap, winning for the day yesterday.