Exhaust System; Recommended Muffler; Fabricated Exhaust Systems - Honda GX630 Technical Manual

GX630 • GX660 • GX690 Technical Manual
E S
XHAUST YSTEM

Recommended Muffler

Honda mufflers and exhaust pipes are matched to the engine in terms of emissions performance, exhaust back
pressure, silencing performance, durability, and installation rigidity.
Consider the following:
Discharge the exhaust gas directly to the open air. Do not install flammable parts or any parts with poor heat
·
resistance properties around the exhaust system or near the discharge port.
The exhaust gas must not enter the cooling-air intake port. Be especially careful when using the exhaust deflector
·
to change the discharge direction.
The muffler and exhaust pipe become very hot during operation and remain hot after the engine has been shut off.
·
Install the muffler and exhaust pipe so the fuel system and other heat-sensitive components are isolated from the
exhaust heat.

Fabricated Exhaust Systems

The muffler type and the shape and length of the exhaust pipe(s) affect emissions performance and engine power. If
you use a muffler other than a recommended Honda muffler, observe the following precautions to maintain the
engine's peak performance:
The shape (bends and elbows) of the exhaust pipe can affect exhaust back pressure. If exhaust back pressure is
·
excessive, it can affect emissions performance and/or cause detonation.
The exhaust pipe ID must be the same size as the exhaust port diameter.
·
There must be no gap between the port ID and the exhaust pipe ID.
·
The exhaust back pressure increases if the diameter is less than specified. If the diameter is larger than specified,
·
the effective width of the exhaust gasket is reduced, causing it to develop a leak.
When the exhaust pipes are connected together before the muffler, make sure that the exhaust pipe length is as
·
short as possible to reduce backpressure.
Muffler volume and design will affect exhaust back pressure. Increase the volume of the muffler if exhaust back
·
pressure is higher than specified.
Exhaust Back Pressure Measurement
Measure the exhaust back pressure at the exhaust pipe, 30 mm (1.18 in) from
the exhaust pipe mounting flange as shown (make sure the test nipple does not
extend beyond the inner wall of the exhaust pipe). Pressure should be as shown
below with continuous load applied. Apply the higher of the two cylinders.
kPa
GX690
mmH O
2
kPa
GX660
mmH O
2
kPa
GX630
mmH O
2
© 2010 American Honda Motor Co., Inc — All Rights Reserved
3600 rpm
Min. Max Min.
7.0 10.0 5.4
714 1020 551
6.7 9.5 5.4
683 969 551
6.5 14.0 5.0
663 1428 510
3000 rpm
Max
7.7
785
7.7
785
12.0
1224
30 mm
9