Just as a side comment, when I was speaking to Clive Padgett (HRC race shop & team owner for those unfamiliar with the name), he said they use Castrol A747 with AVGAS and XR77 with Unleaded Fuel.

A747 is Castor / Synthetic Blend, XR77 is 100% synthetic oil.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30