current rpm, max rpm, average rpm,
total run time, service intervals and
resettable displays. The only trick to
using a vibrating hour meter is that
it must be mounted on a flat
metallic surface via two-sided tape.
We typically mount them on the
head tube gusset. The MXA test
riders were also interested in the
ease of mounting, but after a short
time, we elected to go back to
traditional spark-impulse hour
meters. Why? (1) Two-sided tape
rarely stands the test of time as
well as screws. How do we know?
We lost a vibrating hour meter. We
ended up safety-wiring our vibrating
hour meter so that it couldn’t fly off.
( 2) The power for a vibrating hour
meter comes from a built-in battery,
and in most cases that battery
cannot be replaced. When it dies,
so does your vibrating hour meter.
( 3) Vibrating hour meters cost more
than conventional hour meters.
MXA test riders are lazy also,
and we thought we would love the
wireless feature, but there were too
many trade-offs. We will stick with
MAY 2015 / MOTOCROSS ACTION 179
After we lost a vibrating hour meter, we
safety-wired them to the frame.
THE VIBRATING HOUR METER
I’m interested in buying a vibrat-
ing hour meter. I confess that the
reason I’m going this direction is
because I’m too lazy to remove my
gas tank to wrap the electrical lead
around my KX250F’s spark plug.
But, before I make the purchase, I
thought I’d ask MXA’s opinion of
vibrating hour meters. Good or bad?
ventional hour meters is that they
don’t need any hard wiring because
they use vampire spark impulses
from the spark plug wire to register
rpm; however, the hour meter’s lead
wire must be wrapped around the
spark plug wire for this to happen.
Vibrating hour meters have no wires,
not even spark plug wires, because
they use engine vibration (or, more
accurately, the wave frequency of
the engine’s combustion stroke) to
report engine rpm. As with all hour
meters, vibrating hour meters supply
more than simple rpm. They offer