First piston change. Newbie questions.

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Note, with any tear down for inspection. One must consider the time it’s been used also. Parts can fatigue with time. Inspect the little pins that hold the piston ring from turning. Make sure there still tight in there bores. I’ve seen these pins get loose in other two strokes with these pins that capture the rings. If it was mine I do the cylinder with 1500 grit paper and install a new piston and rings.

Just like my uncles 54 Pontiac that’s been in the garage since his death, the engine needed new seals.
 
With or without the piston ring installed?

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Don’t matter. You want the gauge between the piston skirt and the bottom of the bore at BDC.

If .003 slides in loosely, the clearance is too great.

I had an 066 I was repairing after the JMS debacle on my bench. The piston skirt was chewed up on the intake side from flapping and pushing itself into the intake floor and catching it a bit. The clearance was .009! It actually ran there, I’m not sure how long it would have though. I only took the job to straighten out the belt sander machine work, but as with all of his saws, other issues became apparent.
 
I slid it back on yesterday and checked. I could get a .003 in but it was pretty tight.

I should get my ring in this week and im ready to go back together with the saw.

I did find an OEM cylinder and piston online for $100.00 It says it is part number 503532071 and 5442228025. It does not list it to fit an 86 model saw but according to jacks my cylinder subs up to the 5442228025 number. Im putting this one back together as is but if that is a good price I might go ahead and put it on the shelf.
 
How does it do that?????????
Without getting too technical, in theory, the outer surface of the piston ring is the only part of the piston assembly that makes contact with the cylinder wall.
In a 2-stroke engine there is almost always positive vapour pressure against the advancing end (the top or bottom) of the piston, which exerts force through the tiny trailing gap between the ring and the piston and then to behind the ring, effectively pushing it outwards as the piston slides.
 
Without getting too technical, in theory, the outer surface of the piston ring is the only part of the piston assembly that makes contact with the cylinder wall.
In a 2-stroke engine there is almost always positive vapour pressure against the advancing end (the top or bottom) of the piston, which exerts force through the tiny trailing gap between the ring and the piston and then to behind the ring, effectively pushing it outwards as the piston slides.
Yea that's why it is called theory. Can't prove it and some people don't believe it. Mike
 
Either do the used piston with moly the engine assembly lube and add a new ring, do the cylinder with 1500 grit paper by hand, wash, prelube and assemble, run with the choke on to fume agate the crankcase and cylinder and forget about it.

Or add a new piston/ring and follow the above assembly and forget about it.

Each of my used saws will get a hot compression check, then a leak down test. Who’s ok will get a good bath, lube, sharpen, bar maintenance, new air filter and parked. The ones who don’t pass the compression test I’ll refresh.
 
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