Merlin vs Villiers
No Danny that would not be possible. The Villiers was a two stroke and did not have a camshaft as far as I can recall so it had ports like a model diesel engine which were exposed as the piston went up and down. The Merlin being a four stroke had valves operated by the camshaft (or camshafts) which limited it to going in a forward direction only.
Not a great explanation but true none the less.
ACW