"C J Campbell" wrote in message
news:2007051622001427544-christophercampbell@hotmailcom...

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen too
many malfunctioning magnetos to believe that it could never happen. It
might be improbable, but I would not bet my life on the idea that it is
impossible.
--

On a 2 cycle engine, ignition time is all it takes. Some golf carts actually
work that way. The starter and ignition time is selectable by the direction
indicatior on the dash.

But on a 4 cycle engine, the valve timing would have you intaking through
the exhaust, and exhausting through the intake.