Parts will be a crapshoot at best. The old 'homies' as well as the old Polans and Macs are getting harder and hard to get parts for today. What I do if I do pull a jug is, I remove the base gasket and put a smear of Kubota 3 Bond the base and retorque it but I do measure the after compression ratio to make sure it's not to high, squish is everything.
Easiest and least intrusive mods are of course the muffler and the intake tract (larger carb) and better and less restrictive filtration. Builders all tend to cheap out on air cleaners and undersize throats on carbs as well as restrictive. The more air in and the easier the exhaust exits, the better response you get without major dissection. Stoekel makes some nice air filter / velocity stack combo's and you can buy direct from him btw. Nice guy. Most production saws also have rough exhaust ports and transfers that always can stand smoothing out but that entails removing the cylinder and pulling the piston which can be involved and requires re-torguing the head bolts. Just as easy to modify them externally most times and Nick sells the 5 degree offset flywheel key as well. I like to advance the timing 5 degrees, that always 'wakes up a saw' in my experience but some saws require a special puller to remove the flywheel and remember the flywheel nut always loosens the opposite way the flywheel rotates.
Finally, I always remove the limiter caps on the carb jets (if they have them) because Echo especially sets the mixture rich which causes 4 stroking when cutting but, be cognizant that being a 2 stroke engine, they are prone to seizing if you lean them out too much. I like to adjust the high speed jet just a little, run the saw (in a cut) and then pull the plug and observe the color. Needs to be light brown not white and I'll kill the saw immediately after the cut so the idle jet don't give a false reading. I know you should always cool down the motor after working it and I do, same with starting a saw, I allow it to idle for a minute or so to let the cylinder and piston to reach operating temperature prior to working it. I do the same with my vehicles as well. Thermal shock greatly lessens engine life. I must do something right because my 45 year old 028 Stihl runs like a top (modded muffler only) and cuts like a bear (with a sharp loop). The o28 I own was only built for 2 years and then discontinued. It's an RPM saw and an earmuff required saw and it screams. Too bad Stihl quit making it. I also own a 090 and 075 I bought them new when I bought the 028. Both are in pristine condition and the 090 wears a 4 foot buddy bar while the 075 wears a 28 inch bar and both have full tooth (not skip tooth) 050 chains with Stihl greaseable roller nose bars. Even though both are magnesium cased, no plastic, both are heavy, too heavy to actually use for cutting at my advanced age. Not a square tooth loop fan. Fine for milling but I don't mill and square tooth has to always be hand filed too.
I keep syn gas in both and fire them up regularly. Both have compression releases. You never try to start either without it or you'll leave your fingers on the recoil handle. They are wicked saws. In fact I run syn gas in everything. No e-gas here. I like the Echo Red Armor but it is hard to find in gallons so I also use Tru-Fuel in 50 to 1 for the modern saws and 40 to one for the older ones and I always use either Stihl bar oil or Menards brand, never used motor oil, never. Used motor oil don't have the tackiness required to not fling off and it's usually loaded with contaminates including microscopic metal chips, none of which is good for your saw, especially the chain and drive sprocket and I watch the drive sprocket for wear as well. Almost all of them have wear indicators today so when the chain wears it to close to the wear mark, I replace it. A worn sprocket also wears the drive tangs on the loop quickly. As usual my post is a bit long but I don't mind telling you or anyone else interested what I do and how I mod my saws.
