My main problem is melted O-rings, melted plastic thinfilm breather gaskets, etc. It pretty much destroys all them over a season or two if you let it sit. I’ve taken to letting them run completely dry before storing.
I haven’t gotten around to looking at rings, although I have rebuilt those once or twice. My repair pricepoint is about $100. If it’s over that I fix/rebuild it if the parts are cheap. If not, chuck it and buy another one.
Most parts are dirt cheap for these little 2 strokes, carb rebuild kit <$10 in most cases, and O rings are nothing as well. Even a piston can be found for $25 or less.
O Ring/Piston replacement are less common, but given enough time can need them. I’ve run 2 strokes for many may seasons on cheap 87 octane 10% ethanol gas before I’ve even needed to do a carb rebuild. Usually because the ethanol has made the pump rubber to inflexible to effectively pump the gas... So maybe 30 minutes at most and <$10 I rebuild the carb and am good to go.
Of course if you want to avoid this, you can always hunt down and use the more expensive fuel that doesn’t have alcohol in it. To me, as a home owner just using my weedwacker maybe 30-40 hours a year this seems like overkill.
If I was a pro doing it daily for 8 hours a day I’d probably hunt down the better gas.
I have heard, though I haven’t actually tried it myself, that if you put a tablespoon or so of ATF in the gasoline that this will negate the effects of the ethanol. Also Marvel Mystery Oil is said to do the same thing..................