Having many engine in the 40 thu 53 range (many more 2 and 4 strk thru 1.2)) the ST 40 still gets my vote ringed steel liner $50
it had a very short life as glow and wears a davis diesel head have never had a carb issue sort of a super timex
cheap and works well martin

forgot has the economy muffler too conventional not that hugh garbage can that either siezes or falls off and looks like h##ll