like Bill wrote,Fora Goodyear Engine has his roots in Fora F1C Free Flight engine, longer crankshaft.Not much in common with Fora F2D engine , short crankshaft, 4mm Venturi ,FAI Rules.Fora has a wide range and is not only competing @ F2D market. Peter
What length lines are they on?
http://old.technohobby.com.ua/online-shop/en/fora-25cc-f1c-side-exhaust-googyear-engine