Parts for these are all over eBay. Good medium duty saw. Real mag and aluminum. Fuel lines are an issue. Two sizes used , one sleeved into the other. Can be made out of Tygon tubing and will run quite a while.
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here and read posts on restoring these. Many have been done up real well. Tough enough saws to run and cut well as long as they are taken care of. Good bucking saws because they have side exhaust (not into the wood). Everyone needs one side exhaust saw. Front exhaust is good for felling and stumping.
When you get it home, pull the muffler and stroke the piston up and down while looking in the exhaust port. Minor scratches from bits of hard carbon are OK, but any major scratches, gouges, rough surfaces, etc - it's toast. Compression should be over 100 psi to run well. If not, it'll need rings. It uses points, so the mag will have to come off to service. Not hard to do. Get a piston stop and ease over the edges where it touches the piston when screwed in.
Do not run it on 50:1. 32:1 is much better with quality oil. It's gotta smoke some to be happy
Once the carb is rebuilt, tune L speed jet so it'll idle just below chain-go speed. H jet should be rich enough that it'll 4-stroke some while running unloaded, then clean up and pull hard once in the wood (common tune for all these old saws). Any leaner than that and you'll be buying pistons and rings ...