Rebuilding motor

Jeffrey Walker walkerjl at
Mon Jul 14 20:13:38 PDT 2008

Burning or consuming oil in of itself isn't a good reason to do a complete
rebuild.  BTW, is it burning it, leaking it, or magically consuming it?
(Might have something to do with the de-californication of your bike and the
crankcase ventilation.)

The first and second determinations that I use to determine whether I would
consider rebuilding a motor is a compression test and cylinder leak down
test.  (One uses the starter motor to cycle the compression cycle, the other
is done with the cylinder at either TDC or BDC with the valves closed,
pressurizes the cylinder with air through the spark plug hole and measures
the rate at which the pressure decays.

Its been my experience that if the compression is good, the oil rings are
not excessively worn on the pistons, and the problem is elsewhere... oil
rings and compression rings work together.

If the compression and lead down tests show they are OK, I'd have to think
long and hard about considering the inconvenience of having to add oil every
so often to having a good running motor.  (How many miles are on it anyway?)
I put about 45K miles on my KLR 650 after it started to magically consume
1/2 quart of oil every 500 -1000 miles.  (The consumption rate was dependent
upon how many high-speed highway miles I was riding, which always made me
think that the crankcase ventilation was fuxxored.  It made it a pain to
pack for long trips, having to pack a quart or more in small bottles that I
could easily add, but it was the cost of business as far as I was concerned,
as that bike never once let me down, ever.

Oil consumption can also be just from the valve seals / guides, or from your
crankcase ventilation not working correctly.  Seems to me the majority of
the time when people believe that their motor needs rebuilding it really
only needs the head to be refurbished.

Do the compression testing and report back.

Jeff W.

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