From: "Stoodley: Jon & Martha" 
Subject: Re: New Engine Break-In
Date: Tue, 31 Aug 1999 16:05:07 -0500

Subject: Re: New Engine Break-In
I remember the cool off period being essential back when I had mxers in the
>70s.  I thought it applied to the air cooled machines and was discounted
when
>liquid cooling came around.  That is, the complete cooling. The thought
being
>they get to a stable temperature, not getting as hot.  It is still
>recommended (the cool off) for all liquid cooled motors?
>
>Matt

Matt,
It depends on who you talk to and how compulsive they are. Most tuners I
talk to (that work almost exclusively with professional clients) go for the
cool-off period. These people are into the last tiny bit of performance
(like the kart guys are about horsepower) and will do whatever they think
will give them that last little edge. I know guys that set the jetting on
their roadracers by tearing down the engine and reading the carbon deposits
on the underside of the piston crowns (actually this is a good way to
diagnose possible problems or provide failure analysis but there are simpler
ways to jet a bike).
Don't forget that in "breaking in" a new bike it's not only the rings but
bearings, gear surfaces, shaft surfaces, seals, case to shaft alignments
etc. A top end job on a used bike will probably not need the same break-in
time but it's the old adage: "How lucky do you feel?" I will always come
down on the side of reliability in making engine design decisions because
"If you don't finish, you can't win."
Most of the new bikes probably don't need the type of breaking in that I do
but I just like to stack the deck in my favor and old habits die hard.

Jon Stoodley
JSE Racing