- The Yamaha Blaster engine, like the Honda TRX engine
and many others uses a gear driven weighted counter
balancing shaft. The lash between its gears - the normal
tolerance for straight cut gears meshing with each other
- can cause a noise which under some conditions sounds
like an engine knock. While the engine accelerates, the
balance shaft is constantly trying to decelerate - hence
the noise, when the engine decelerates the balance shaft
has inertia to try to keep it going - more noise. Running
under little or no load at any RPM will bring this sound
out the most.
-
- Real engine knock (detonation) could immediately
destroy a piston at high revs in a matter of seconds. The
gear lash "slapping" noise associated with the counter
balancer has made more than one Blaster, TRX or LT owner
hand their quad over to a dealer for a rebuild. The rider
with a careful ear can detect the difference between the
two sounds and continue to ride safely knowing that
everything is OK. The best way to know the difference is
that if the noise is really loud and your engine is still
running, its probably the balance shaft because if it
were detonation you'd be pushing the quad by the time it
got that loud. Detonation, the kind that destroys engines
is rarely heard and if it is it is just before a
meltdown. If you've heard real detonation at high revs,
you've visited the dealer for new parts shortly
thereafter.
-
- Rick
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