ORIGINAL: RaceCity
Typhoon...how much prop are you using on those old .45's? The older vintage "B" frame .40's and .45's were arguably VERY overcarbureted using a carb bore similar to that of the .60 size engines. This, combined with a too-big prop and one could imagine some transition problems arising. Overbore carbs are great if top end is the only objective.
The carb from a current .45/.46 should work well provided it's properly tuned.
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I talked with Duke about this some years ago. He said to let the engine rev up and then it would carburet properly. A 10x6 is all you need on a Fox .40 or .45. Larger than that and the carb is too large. Remember, these are old paradigm engines and were made long before anyone used an 11x6 or larger on a .40 to .45 sized glow two-stroke. An alternative might be an 11x5. Also, those old large crankcase .40 - .45 engines were made to run on Missile Mist and they will run rich in the midrange if ran on lower nitro fuel. Small prop and a bit of nitro couldn't hurt. They are going to be powerful, but LOUD.