TRX
700XX Engine / Drivetrain
- Continued |
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Honda
TRX 700XX dry-sump design
eliminates an engine oil
pan, which contributes to
a shorter engine height
and consequently a lower
center of gravity. Also,
the oil tank, coolant overflow,
and fuel filter are positioned
low on the frame for additional
reduction in the center
of gravity.
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Coolant is routed through an aluminum
radiator with a 28mm-thick core—the
same core size as a CRF450R motocrosser.
A special wire-mesh filter in the
oil hose connector and a custom bend
of the oil return pipe protects the
oil from sloshing and aeration in
its separate brazed aluminum tank.
This dry-sump design eliminates the
oil pan, which contributes to a shorter
engine height and consequently a lower
center of gravity.
Several enhancements are made to
the engine to simplify its operation
and enhance durability. An automatic
decompression system is activated
whenever the electric starter is
engaged. The starter-motor housing
is incorporated into the engine
crankcase casting and a disc-type
torque limiter minimizes shock to
the starter mechanism.
Power is channeled through a five-speed
gearbox with Reverse and is transmitted
to the rear wheels via an ingenious
centered chain drive system. Conceived
with the goal of maximizing the
architecture of the long A-armed,
double-wishbone independent rear
suspension, a row of final gears
located after the countershaft positions
the drive sprocket just 33mm left
of the 700XX's centerline. The proprietary
design allows the chain and rear
sprocket to be placed virtually
in the center of the rear of the
ATV. This produces numerous benefits,
including the use of longer A-arms
and axle shafts. Longer A-arms minimize
wheel camber changes as the suspension
travels up and down—a handling
benefit—and longer axle shafts
mean that CV joints operate at less
extreme angles, benefiting power
efficiency and long-term durability.
A further benefit of the design
is simplified maintenance.
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| TRX
700XX rear spocket (left)
& rear brake rotor (right)
are each located 33mm from
the centerline, which is virtually
in the center of the rear
of the ATV |
TRX
700XX ulitizes long rear A-arms
& equal length axle shafts
to minimize wheel chamber
changes as the suspension
travels up and down |
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Honda
TRX 700XX has 10.2"
of ground clearance
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Two more features of the gearbox
and final drive are worth noting.
First, top speed in Reverse gear
is controlled by monitoring both
actual speed and crankshaft speed.
When vehicle speed is no less than
12 mph and the engine speed is no
less than 3050 rpm (equivalent to
12 mph), fuel delivery to the injector
is restricted. The second noteworthy
aspect of the gearbox is the engine
reduction ratio at the drive sprocket:
1.087:1. This was done to permit
the fitment of a smaller-diameter
rear sprocket, which in turn allows
the sprocket receiver assembly to
be located lower on the frame. In
addition to lowering the center
of gravity, the smaller diameter
of the sprocket and its assembly
also improve ground clearance.
