Hi
I got a B40 too... which wind do you have? also is it a S or L? factory mounted 4,4:1 gearbox?
a B40 performs as a 72 4 stroke, I use mine in a Kyosho CAP232 40 size, on 10 round cells. hovers and pulls out!
previous I had it in a diablotin mini usper, very good power/weight ratio.
I would suggest an E3D,
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