HI
DO SEARCH THE FORUMS here for much more info on the 91 FX probleman easy quick fix is to cut you present needle valve off of the back plate and mount it somewerethis does look like an air leak problembut in my opinion it is not-it is a heat transfer problemDO NOT LET TOWER OFF THE HOOKthe problem with the engine is with the earlier engines-so it does not matter if they are still selling them-i have one of the first engines and the new parts solved my problems it did take me 2-3 months of some difficult days at the fieldto get the engine running excellent-i was getting air bubbles in the fuel line to the carb and needle valve -ONLY AT MIDRANGE from day one-but no internal damage thank goodness i think the engine comes up a bit short on power for its sizeturns a 13/6 APC -my OS 1.08 FSR will blow its doors off15/6 APC as will my 75 AX 14/6 APC BEST REGARDS TONY