MTD Garden Tractors User Manual page 208

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the engine should be checked and running at
3400 to 3600 RPM. This should be checked
with a tachometer by a qualified dealer.
The blades running at the proper RPM develop
a vacuum lift action. This is created by a com-
bination of things, mainly a deck designed with
baffles in the front and rear of the deck. The
deck depth and controlled flow design helps to
develop a deep vacuum action lifting the grass
for cleaner, sharper cutting and efficient dis-
charge of the grass out the side or to the rear
for bagging. This then brings us to understand
the importance of discharging the grass. To
accomplish this most effectively a full baffled
deck housing is needed. That is also why the
most effective decks for mulching are designed
like a donut. The depth is important because
after the grass is cut it must rise into the dome
of the housing and as it falls to the ground the
grass is cut many more times by the inner
angles and edges of a special mulching blade.
Most of our walk behind mowers are designed
to be what we call three-in-one mowers, mean-
ing that they will mulch, side-discharge and
side or rear bag grass. Blades must be prop-
erly sharpened, following the original angle
and then checked for balance. If the blades are
dull and nicked on the cutting edge this will
tend to tear the grass rather than cut it. Mulch-
ing blades are more critical and most often it
would be better to replace the blade rather
than trying to sharpen the varying angles and
possibly lose its effectiveness. If blades are in
question, measure from a level surface to the
blade tip, using a rule or tape measure. The
blade should be checked and then rotated to
the other end 90 degrees. The measurements
between the blades should be the same and
no more than 3/16" height difference when the
blades are tip to tip. If more than the 3/16" is
discovered and the deck is hanging properly
from the tractor, the blades should be removed
and checked for straightness.
The sharpened edges should lie flat against
the surface plate. If they do not, it is possible
the blade is bent or warped. The blade can be
placed in a vise and straightened or replaced.
If the edge of the blades are found to be
straight, it is then possible that the spindles or
spindle area in the deck is bent or warped from
hitting an object, root or curb. Each blade spin-
dle can be checked and removed from the
deck and placed in a vise by the bearing hous-
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ings. By rotating the blade by hand a bent spin-
dle can be detected by wobble. If this is found,
the spindle should be replaced. Often this is
checked when it is felt that bearings have worn
out prematurely. Bearings and spindles often
take damaging shocks that the user is now
aware of, or quickly forgets that a few roots
etc., have been hit.
MISSILE DEFLECTORS: All of our mower
decks are equipped with a missile deflector to
direct the flow of grass out the side of the deck
at a safe angle and mowers should only be
operated with the deflector in the down posi-
tion. During our testing procedures we inject
steel balls and nails under the deck while the
mower is running so that we can determine the
angle that these objects will be discharged.
The regulated height that any item can come
out is no higher than the knee.
Decks should always have this deflector prop-
erly installed on the mower housing. If for
some reason that this deflector is off the
mower during the warranty servicing, a claim
can be submitted for replacement. A mower
without a deflector can project STONES from
the driveway, and the NAILS that fell into the
lawn when the roofer was installing the new
roof and of course, no one could find them, but
the lawn mower does find them when you least
expect.
DECK BELT GUARDS: Belt guards must be
properly adjusted and kept in place. The belt
guards (hex bolts) on the engine pulley and
belt guards on the deck pulleys should have a
minimum of 1/8" clearance. Belt guards which
are rubbing the pulleys and/or belts can cause
the belt to be subjected to excessive heat. The
possibility of a belt rolling over is greatly
increased when this type of condition exists.
The engine pulley and the deck pulleys should
be free of any nicks or dents and the pulley
sheaves edges should be smooth and free of
burrs.
It is also important to then understand that
these belt guards are not only to keep the belt
on the pulley, but that they are also needed so
that the belts trap-out against them. When the
belt is disengaged, the belts then are pre-
vented from continuing to travel. Understand-
ing this, it is then easy to understand the
importance of the proper belt size and con-
struction. All MTD belts are constructed
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