On 10/29/2011 9:23 PM, Ed Huntress wrote:


"John G" wrote in message
. au...

Gardner has brought this to us :
On 29-Oct-2011 21:20, engineman wrote:
I'm wondering if all 2
cycle engines will run backwards or not?

Most can. The ignition timing will be off -- the spark will be late --
and the engine will not develop much power.

__________________________________________________ __________________
Gardner Buchanan gbuchana(a)teksavvy(dot)com
FreeBSD: Where you want to go. Today.

Ship board diesels are commression ignition (just like other diesels)
and hence do not rely on ignition timing. (I believe)

--
John G.

The motorcycle hypothetical caused me not to reply initially, because
there are two issues the the ignition, as previously mentioned, and
the type of intake valve used.

Battery and spark-coil ignition, as the previous poster said, will be
off on timing but may allow it to run. Electronic ignition may be
closer. Magneto ignition probably won't allow it to run backwards at all
because the pulse to create the spark won't occur until well after TDC.

On the valves, reed-type or piston-port, yes. Rotary-valve, probably not.

I started a lot of model airplane engines backwards when I was a kid,
unintentionally. They had reed valves (my little Cox engines) or rotary
type (McCoy Red Head). My recollection of the McCoy, though, is that it
would start backwards, so it may have been fairly symmetrical. The Coxes
did it all the time, if you weren't careful.

Those engines were glow-plug ignition and, like compression ignition
engines, didn't care which way they were running from an ignition
standpoint.

Is anyone familiar with the old drag-saws used to buck up logs. I
remember the engine could be started either way, depending on the way
you spun the flywheel.

Paul