This time it's the old topic of 912 ULS kick-backs on start up. After a couple
of days during which our group members pondered possible causes of this recent
phenomenon, following a long period of relatively trouble-free starting, we
reached
the conclusion that the battery has become elderly. The gradual slowing
of cranking speed while engaging the starter, creeps up unnoticed over a period
of years.
A new battery fixed the problem most convincingly, whizzing the propeller around
with great enthusiasm. But one of my group members raised this question "Why
should there ever be any kick-backs at all, even with a tired battery,
considering
that we have the latest CDI boxes in addition to all the other measures
recommended to prevent it? After all, the built-in temporary retardation of
timing
to 3 degrees ATDC while starting, should guarantee that kick-back can't happen
even with an old battery!"
The only "explanation" I can conjure up is that when overall battery voltage
reduces
with age and while it drops even lower during cranking, the built-in deliberate
delay in spark being triggered until after TDC while starting doesn't
function, or only works partially.
How's that for a half-baked theory?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=487866#487866
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