tea and cakes, but broke down on the way. A duff condenser was suspected, but no - spark, fuel and everything else was present and correct. Ho, hum, and home here we come.
Next day the impoverished owner stuck the contents of the MV's recently filled fuel tank into his Triumph Adventurer and set off. After exactly the same distance the MV had managed between filling up and failing, this Trumpet was blown. White spark plugs were the only clue that something was wrong.
But the weirdest thing? Fresh (different) fuel and flushing was all it took to get both bikes running. The culprit seems to have been a famous petrol brand's premium product, but in these litigious times You Can Be Sure Of...me keeping the details to myself.