I use concentrated dish washing liquid for saw plastic cleaning Pete.
I had a Shindaiwa 757, good old saw, sold it to a mate for $200 for cutting firewood.
What did Chippy do exactly?
Or shouldn't I ask. :)
I'm very happy with Husqvarna LS+ it's semi synth and JASO FD rated.
You can change over to it with only a minor retune if needed.
40:1 in all my gear and BP95.
Costs around $140.00 for 10ltr.
It was used last winter then left sitting since, it was given to me today and I haven't tried to start it, too many other things to fix.
The previous owner said it runs but not too well up in the revs.
It's an 032av electronic quickstop,
Looks like the washer has worn into the plastic worm drive.
I'd be replacing it and the other two worn parts(v ring and dust seal)
You should get a new inner bar plate too, 501 81 48-01