RE: Kyosho GX.40 engine
In my humble opinion, it identical to a magnum engine, for some reasons:
The thrust washer is the same to the magnum's.
the exhaust port in the block, where it meets the muffler is unmachined (it has a rough finish) as the magnum
The barrel looks identical to the magnum.
The rear needle assembly is identical to the magnum.
Even the drilled muffler plate that goes inside de muffler is the same
And magnum rules!!