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Re: Spark Plugs and other stuff.

Just one note on bearings and seals.  Ball bearings are rated based on 
the design life under their designed load.  A typical rating would be 
the B10 rating, listed in a number of hours where 10% of the bearings 
would fail.  There is another hour rating at 5% and 1% etc.  The actual 
numbers aren't important unless you are the design engineer, but the 
concept is important to us users.

If a bearing or seal fails at, say, 10000 miles, it was likely one of 
those 10% (or 5%, or 1% depending on the selection the engineer made) 
that are just going to fail.  So you replace it and move on.

If, at 10000 miles (or 120000 miles in Bob Silas's case) you decide to 
replace a bearing or seal that hasn't failed, you may not have done 
yourself any favors.  The fact that the original bearing hasn't failed, 
means it's one of the good ones.  You have no idea if the one you put 
in is a good one or not.  So it's a crap shoot to some degree.  I have 
no idea what the design life of the bearings in our bikes is, but it's 
something to think about when you decide to change out a good bearing.

This above logic also applies to seals.  If the seal isn't leaking, 
don't mess with it.  If you take something apart anyway, you should 
always replace the seal, because you could well have wrecked it when 
taking apart the item.

Some of this goes back to the old saying:  If it ain't broke, don't fix 

Bob,  Don't get me wrong here.  I'm not saying you shouldn't have 
changed out the parts you did.  After all, 120k is a bunch of miles.

OK,  Time to go back to riding.

Bob Hadden '05R12GS, '62R27

On Jun 10, 2005, at 9:26 AM, Robert Silas wrote:

> Clive,
> <snip>
> The cage which holds the 19 balls in place in the large roller bearing 
> broke, cut the seal and let the oil escape from the final drive.
> I had at least 50% more milage at that point and I figured better 
> change bearing and seal, which I did.  The bearing which I replaced 
> was in perfect shape.
> <snip>
> Regards
> Bob Silas