In a message dated 4/29/2004 4:31:43 PM Eastern Standard Time, N2VZD@aol.com writes: i do not think poping thru carbs is because of jet size...valves adjusted too tight? or other issues. >>>>>>>>>>>>>>>>>>>> Any to lean condition will cause the engine to "pop" back through the carbs. Try unhooking your chokes and see what happens when the engine is cold. Ken Hand