Chainsaw Repair

Get the  viton orings and not nitril or neoprene which is normally stocked  hardware store/car parts .
I don't have a sthil saw but the local guy says he routinely exchanges or gives (free) new flippy caps to guys that have older sthil saws with swollen orings.

On poulans not only do the orings get screwed up , but the caps them selves get swollen from the E-10. You have to buy a new cap/ring and wash it and swap it out ever now and then since it will "recover" if left to "air out" for a year. I've gotten a few for friends for some of the old (early 90"s) 2150's that I have worked on.