backwards rotation

[Mike Arman]

Some two-strokes will run in either direction with nothing more than moving
the ignition timing. Every once in a while, someone's dirt bike starts
backward - they kicked it, it backfired, and is now running in the "wrong"
direction - most amusing when they drop the clutch at the start of the race.


With four-stroke engines, there is more involved.

One of the minor issues concerns oil seals. Some of them are "directional",
and have small ribs molded into the rubber part near the lip. If the engine
is turning the "wrong" way, the ribs direct the oil toward the lip, not
away from it, and the seal doesn't work very well since it is overloaded
with oil.

Mechanical advance distributors are direction sensitive, and oh, yeah, so
are oil pumps. If the oil pump is turning the wrong way, you won't have a
chance to discover the oil seal problem  . . .

You can buy reverse rotation cams, and they should come with the correct
bits to make the oil pump and distributor happy. This can be a problem with
buying used parts - all you get is the cam, and you discover later that you
need some other tiny bits of unobtanium to make all this work  - ask me how
I know. Something about a reverse rotation 140HP Corvair engine into a 914
(in a past life).

Best Regards,

Mike Arman