On Sat, 29 Oct 2011 18:20:28 -0700, engineman wrote:

John,

Here is a question for you and your metalhead group.

Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
it. Suppose that you got on it and turned on the ignition but didn't
hit the start button. Instead you depressed the clutch lever and put it
in 1st gear. Then four of your not so bright friends, two on each side,
pushed you and the bike BACKWARDS!! Remember there are two each side so
they should be able to keep you from falling over. After the bike gains
some momentum you pop the clutch. Now, the question is: WILL THE BIKE
START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why not? The reason
that it comes up is that I read about a new class of ULCCs
(UltraLargeCrudeCarriers -- Way big mutha oil tankers) that have 2
cycle diesel engines with NO transmission, clutch or reduction gears of
any sort. The drive shaft comes out the back of the engine and goes out
the back of the hull and the propeller is bolted directly to the end of
it No gears, no clutch, no nothing. The way that they reverse it is by
shutting of the engine and then restarting it BACKWARDS!!?! It is
designed to do this, I'm wondering if all 2 cycle engines will run
backwards or not? Inquiring minds want to know.


Common glow plug aircraft engines will. Easily because their intake,
exhaust, and ignition timing are symetrical about TDC.

Two-stroke spark ignition engines will probably not, the spark is
advanced; extremely unlikely if they are also assymetric breathers.

Larger diesel engines can/will have assymetric intake, exhaust, and
injection timing. To run backwards you just change that timing so
it works the other way.