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RE: oil filler cap

Mike <mylovelyhorse@xxxxxxxxx> wrote:

>Is it your experience that this happens, then?

No, I have no experience of this nor am I aware of any.

But it is a possibility.

Engineers among us know about something called FMEA (Failure Mode Effects
Analysis) which is a tool for estimating the likelihood and severity of system

Basically, you try to imagine every possible/plausible failure mode in your
system and for each of them rate 3 things on a scale of 1-10:

1. Probability of occurrence (10 = virtually certain)
2. Severity if failure occurs (10 = catastrophic)
3. Probability of detection (10 = undetectable)

Ideally, you assign values using statistical data from similar systems; but
more often it's just a SWAG.

You multiply these 3 factors to obtain an RPN (Risk Priority Number).  You
tackle the failure modes with the highest RPNs first, i.e., apply the Pareto
Principle (AKA the "80/20 rule"; 20% of things cause 80% of problems. It's how
you get the biggest bang for the buck, and if I had only one wrench in my
quality assurance toolbox, Pareto would be it).

For this failure mode, Occurrence is very low. But Severity is high, and
Detection is also high (assuming a saboteur replaced the cap after his
dastardly deed, I might not notice until I'd started the engine and
distributed the contaminant through my engine).

Maybe Occurrence should actually be 0, meaning it never happens. That would
make the RPN = 0 even if Severity = 10 and Detection = 10.

But that doesn't mean it couldn't happen, in my book; so I'd still rate
Occurrence = 1 which means RPN might be as high as 100.

If you think about it, with these bikes the RPN for just about every failure
mode is quite low; they've been addressed by the factory. Otherwise there
wouldn't be so many of them with such high mileage.

I'm just going after a "low hanging bunny", i.e. quick, easy, and relatively
cheap insurance.

Assuming I buy one at all, which I probably won't. Not because I wouldn't like
to have one, but if you saw my credit card balance you'd understand.

John D

p.s. Sometimes just for fun I'll do FMEAs for things like climate change,
asteroid impact, global pandemic... ;)