no cylinder cooling just fins on the heads, I bet the rearmost ones got hot, they must be cast iron pistons and cast iron bores, and plenty of lubrication plus plenty of clearance, I love it, just love it, totally unpractical, but I still love it.
CLEM
certainly beats my mini engine ridgid Triumph complete with mini gearbox, I called it a morumph, (Morris/Triumph) one blocked driveshaft and the sprocket on the other, oh dear, should not have started that one, ruined bike and cycle parts wasted engine. but what you do at 19 is not what you do at 30+ and am now 72