On Aug 14, 1:00 pm, passenger 1957
wrote:

There's a tooth missing.

The ring gear should be replaced at overhaul. If there's a
tooth missing, it's likely pretty old, or the starter had engagement
issues. It should be engaging the ring gear promptly, before the
starter really winds up, and if the starter drive is sticky the teeth
will get worn quickly. On a four-banger there are two places on the
gear that get it the most, both where the prop tends to stop on
shutdown.
The drive bendix on a Lyc needs lubing with silicone spray
lube, and it's really hard to get at. Any other lubricant will attract
dust and create a sticky sludge that sooner or later causes engagement
problems, tearing up the ring gear, and then seizes the drive splines
and the starter won't engage at all.
Many starters (and batteries) get replaced unnecessarily
because the solenoids are old and their contacts are corroded or
burned. Any resistance across those contacts causes a large voltage
drop because of the high current flow, and it can be verified using a
voltmeter across the studs while cranking. There shouldn't be more
than a volt or so of drop. Both the master and starter solenoids
should get replaced if this is noted.
Some pilots just keep cranking if the engine is flooded or
cold or has a bad mag or whatever else is making it reluctant to
start. Good way to bust a starter. Lycoming recommends something like
a ten-minute cooldown after three ten-second cranks. Starters have no
cooling system and use a tremendous amount of current that generates a
lot of heat.The commutator segments are set in plastic which overheats
and throws the segments, and the field and armature windings get hot
and burn off their insulating varnish and short together. Things
really get hot then.
Killing a battery with the starter will often ruin it
permanently; I don't know how many batteries we've replaced after
someone ground them right down, sulfating them so bad they wouldn't
take a charge anymore. Got to think, Pilot: why won't it start? What
should I do besides just cranking and hoping for a miracle?

Dan