I don't think that anyone has wanted to reverse a Enya VT-240 engine before. Enya didn't normally made reverse rotation camshafts for their four stroke engines either.
But my first inclination is to say no, that you can't do it. But then maybe there is a way though. I have not tried it but one can reposition the cams on the Enya four stroke engines to achieve reverse running. So it is theoretically possible that one could do it on the VT-240 too. I have not tried it though so I cannot say that it works.
Here is a link to information on how to do with with some Enya single cylinder four stroke engines.
http://www.modelrectifier.com/resour...enyarevrot.pdf