Re: Detonation problems

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, M Edler <m.m.adler@domain.elided> blurted out:

>Any suggetions?  Also I noticed the 196E timing is TDC and idles at
>700-725 rpm: where as the 196 is 4BTDC and idles at 450-500 rpm.  Should
>I try the other timing mark? How will that do on gas performance?

Matt,

"Run on" is generally caused by the engine getting too much of the air /
fuel mixture after the ignition has been switched off.  Many times this is
because the throttle plate in the carburetor isn't closing enough... like
when the engine is shut off with the choke on.

For starters, I'd check very carefully for vacuum leaks... either hoses or
around the carburetor mounting plate.  A vacuum leak admits more air into
the engine, even when the throttle plate is properly closed.  You might
also experiment with trying to simply degrease the idle rpm a little at a
time to see if that helps.

There might also be an ignition system problem (wiring) of some sort that
results in the ignition not being completely shut off.  There could be a
slight amount of voltage being supplied to the coil after the key is turned
off.  This is pretty rare.

The last couple of things I can think of are severe carbon deposits in the
cylinders or too hot spark plugs (heat range).  Heavy carbon deposits and
low octane fuel can combine in a situation where the carbon glows red hot
and ignites the fuel... even with no spark from the spark plug.  A too hot
spark plug can also get red hot and ignite the fuel without a spark.

Regards,

John
-------------------------------------------------------------------------- 
jlandry AT halcyon DOT com    | "A fear of rebuilding automatic
Conservative Libertarian      |  transmissions is a sign of retarded
Life Member of the NRA        |  sexual and emotional maturity."
WA Arms Collectors            |                          - Sigmund Freud
Capital City Rifle & Pistol   |                  "General Introduction
Commercial Helicopter - Inst. |                   to Mechanical Analysis"