MS460 Compression 120 psi

[sharkey]

The other consideration when replacing only the piston rings in a two stroke engine is if the engine is a piston ported design, and this one is, that the piston skirts also wear.  Maybe finish out the season with it as is and then replace the piston and rings, crank seals, fuel lines and filters, kit the carb, etc and set it up fresh for next season.

Baileys should have a Meteor piston kit for the saw and also have the gasket set, seals, filters etc     

[boobap]

Sharkey, so every time you replace rings, you replace the piston? Even after a visual inspection reveals no transfer or any other signs of "OBVIOUS" wear? Just curious...my thinking has always been that a piston should never touch a cylinder wall. That being said, I understand the clearances are tight and when I say "never touch the walls" I mean that oil is between them...so in theory wear should be minimal.  Just curious... 

[Michael]

I bet none of you guys knows what the compression is on your car and yet you drive it every day. Let that compression fall a little on a $400 saw and it's "let's change the rings!" Scheese. And in case anyone doesn't know (and seems like a lot don't) the main thing needed is a good piston. A  badly worn piston won't come up with additional compression with new rings. I know you don't believe it because you are used to four strokes but I have put together 100s of saws. Have you?

[boobap]

you still haven't answered the question...how does a piston wear when everything else is working properly? the rings and cylinder will...come on, help me out! 

[Michael]

you still haven't answered the question...how does a piston wear when everything else is working properly? the rings and cylinder will...come on, help me out! 

Well the piston is the softest thing there. The nikisil is very hard. The rings are iron. When the dirt, worn iron from the rings and contaminates in fuel interact with the piston, running up and down the cylinder at 13,000 rpm, it wears on the piston. Every up/down stroke causes the piston to go from pushing on one side of the cylinder to suddenly and violently rock to the opposite wall (once at the top and once at the bottom). That is 26,000 cycles a minute. It is a wonder that the piston lasts as well as it does!