The related issue is not likely causal of vapour lock. The cause is likely due to the design of the fuel delivery system between wing tanks and gasolator mounted on the firewall. These inherent flaws have been rectified within the 2016 Virus SW121 variant onwards by employment of an Andair twin coupled fuel/return selector valve and vapour accumulator tanks behind the rear cockpit bulkhead for each wing. All other earlier Sinus and Virus airframes employ a seperate fuel selector valve at each wing tank with the fuel return feeding back to the left wing only. This allows a selected right tank to be pumped dry within 15-20min flying if the left tank is full, causing premature unexpected fuel starvation. This fact is well documented upon other forums along with the official responses offered by the manufacturer, which, at the time was, "fly with the left fuel valve partially open"... It could be presented that the response is questionable, inadequately addresses a critical safety issue, has been recognised by the factory as a real issue due to the upgraded delivery system of the 2016 Virus SW121, and may leave the manufacturer exposed to serious legal action for not issuing an AD to rectify known existing threat to operator safety of pre SW121 produced airframes.
Images of fuel delivery systems attached for explanation.