Subject: Re: pinging....
Author: Patrick Hayes
Date: Jul 30, 2004, 8:03 PM
Post ID: 1717258589
Retarding the timing would be a good start. Remember, the ignition
engineering curve was designed for '74 gasoline and the current US
mixture is crap (especially in California).
The other alternative to examine is age. How many miles on this baby?
The Guzzi valve guide has no oil seal. After about 30K miles, the
guides wear and allow the suction stroke to suck an air/oil mixture from
the rocker chamber down into the intake channel. Not enough to cause
smoke, but enough to cause ping. Oil contamination of the combustion
mixture is a serious contributor to ping. Miniscule amounts of oil will
drastically alter the "relative octane rating" of the vaporized mixture.
Consider doing a valve job. Have new guides installed. Maybe have
someone custom modify them to handle guide to stem oil seals.
A third option is to consider new centrifugal advance weight springs.
The original springs get weak with age and heat. The weakened springs
allow the advance curve to advance too quickly relative to rpm. New
springs will restore that youthful surge by holding the weights back
(=retarded) for a few more revs.
Patrick Hayes
Fremont CA