30:1 for the premix. Any good fully synthetic oil will be fine, I use Rock Oil Synthesis2.
If it's not been refreshed in the past already, it would be due an overhaul. But if it runs ok....
Cranks are amazing so long as you use a decent oil, pistons the same. It's only when you start meddling that you use a lot of pistons, or if you are a generally poor mechanic like me
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More **** two strokes than you can shake a **** stick at.