piclist 2008\08\18\163136a >
Thread: Jet ski -- possible ways for the water to get in theengine?
www.piclist.com/techref/index.htm?key=jet+ski+possible
picon face BY : Richard Prosser email (remove spam text)



Carl,

I really can't figure out how an engine "going hydraulic" would do
that sort of damage. It looks to me more likely that

a) The valvestem broke, probably a fatigue failure.
b) The valvehead rattled around the combustion chamber for a while,
damaging the top of the piston, the head & the spark plug and possibly
other valves.
c) At some stage the valvehead got sufficiently jammed  to stop the
motor and posiibly displaced the head enough to allow water in through
the head gasket. (IIRC there was water in the cylinder when the head
was removed. It could have seeped in later anyway from the
waterjacket.

See if you can get a closeup photo of the break in the vavestem.
Fatigue breaks are quite characteristic and if that's the root cause,
you're off the hook. What you would be looking for is a series of arcs
across the surface of the broken metal caused by crack progression.
I'm sure there's some photos on the web somewhere
(http://en.wikipedia.org/wiki/Metal_fatigue shows an aluminum piece
with fatigue crack growth).

Just an opinion of course!.

RP

2008/8/19 Stephen D. Barnes <stephendbarnesRemoveMEspamcavtel.net>:
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> -
<d02e69350808181331t160b38b7hc23c71d1db870a93@mail.gmail.com> 7bit

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