Attachments :
> service, but wait until 2500". >>
>
> My mechanic said the same, based on experience more than training. He
also
> said that after the first adjustment it was not necessary to adjust again
> during the normal (whatever that is) life of the engine. I would set the
> valves on the very loose side of spec at 2500 miles, that's what I'm going
to
> do, then put a lot of miles on it without taking the valve cover off
again,
> like maybe for three years.
>
> Pete the Streak
What, this argument again? Look, I don't care how many KLR's your mechanic
didn't adjust the valves on. He was not the design engineer, and I
seriously doubt he's been schooled in fatigue life, mechanics and strengths
of materials, or any of the other countless calculations that must be
performed when making a mechanical design. All he has ever seen are the
bikes that came through his shop, and that isn't enough. Only Kawasaki has
all the statistical data on their product worldwide.
When studying mechanical reliability, you can't analyze data empirically.
You have to break the problem down and analyze it statistically. Engineers
when designing for reliability don't care where the mean values are, they
care about the deviation from the mean, and the shape of the distribution
curve. Failures don't occur in the mean range, they occur out on the tails
of the curve.
In engineering, we will never know any absolute, so a factor of safety is
used to try to accommodate the unknown. The strength of a material is never
known exactly, nor its fatigue life, nor any of the other hundred aspects
that each play a small part in reliability. It is this way for all
engineered materials. Don't believe me? Get yourself a box of 1/4" bolts
and a micrometer and start measuring diameters. Then apply loads to them
and see where they break and how much force it took. I have spent much time
in the lab doing just this sort of thing.
I have attached a simple drawing to illustrate my point. On the first graph
are two distribution curves. The one on the right represents the
distribution of the strength of the valve train components to withstand
fatigue. The distribution on the left represents the cyclic loads that the
valves experience during an initial 2500 mile service interval, (as the
valve tolerance adjustment changes during break in.) Note the distance
between the mean values, and the area of the curves' overlapping tails where
failure or damage is likely to occur.
To minimize that probability, you move the mean values farther apart, as I
have done on the second graph, where the curve on the left now represents
the cyclic loads applied during a 500 mile interval. Note that the area of
probable damage is much smaller, so the probability is therefore lower of
failure.
This is just a general example, and the actual analysis is more complicated.
But it proves my point. It isn't important if you crack open your valve
cover only to discover your valves are perfectly adjusted. By not checking
you are rolling the dice. Kawasaki included this interval on their
maintainence manual not because it absolutely needs to be done, but to
absolutely ensure that any problems in their manufacturing process and
assembly will be discovered before serious damage occurs, and they don't
have to shell out money for warrantee service, and lose a valued customer.
Another reason is that they can't count on the operator to limit the RPM
during the break in period like they are supposed to, they have no control
over that, so they try to compensate for that unknown with their maintenance
schedule.
My last argument is that you shouldn't be paying a mechanic to do a basic
service to your bike that you should do yourself. I don't care how limited
your time is or how much money you make, you can't afford not to do it
yourself, because it is the only way to ensure that the job was done
properly, and it will familiarize you with the bike. It has been my
experience that mechanics don't screw up major repair work, it is the small
routine maintenance they always screw up on, little things like using an air
impact driver to torque my wheel nuts on my Rodeo so that they stripped the
threads, and I just went in there for a tire rotation and balance. Of
course it wasn't until a month later before I discovered it. Can you
imagine my rage to discover that I couldn't remove the wheel nuts with a
tire iron in my driveway and had to use a breaker bar? Can you imagine how
much more angry I would have been if I had to change a flat in the middle of
nowhere? Get my drift?
My two pennies
Jeff