Chicken and egg question

[geoffwga1]

OK,in an earlier post I mentioned the noisy blowup of my 72 Norseman motor.When I began to dismantle it to see if i could find the cause the first thing I discovered was that the flywheel key had sheared and I began to wonder in what way was this related to the blowup.I can not think of a way in which the flywheel shearing would have caused it but maybe I'm missing something.On the other hand I can see how the sudden stop of the motor when the con rod came through the crankcase could possibly sheer the flywheel key.Does anyone have any ideas on this ? Am I on the right track and the cause was deeper inside the engine.
Geoffwga1

 

[orbanp]

Re: Chicken and egg question

Hi Geoff,

You are right, the key was probably sheered when the engine suddenly stopped. A sheered key most probably would not lead to fatal mechanical engine failure.
There must have been some fatal problem with the con-rod bearing, like lack of lubrication, or some hidden material problem that led to breakage.

Peter

 

[geoffwga1]

Re: Chicken and egg question

I think you are right Peter,though I have had this motor for a couple of years now and it's been pretty good and reliable I have come across little things here and there that make me suspect it had been tinkered with and not reassembled very carefully.If that applied also to the innards it would not surprise me and would explain things to a certain extent.Oh well,win some ,lose some.Now to start looking for a new powerhead.
Cheers