ENGINE AND TRANSMISSION
Page H-6
Repair and Service Manual
Read all of Section B and this section before attempting any procedure. Pay particular attention to all Notes, Cautions and Warnings
Spark Plugs
Use care not to overtighten the plug.
Overtightening can damage the alumi-
num cylinder head threads.
Do not sand blast spark plugs. They should be
cleaned by scraping or wire brushing by hand
and washing in a commercial solvent.
Tool List
Qty. Required
Ratchet, 1/2" drive ....................................................... 1
Torque wrench, 1/2" drive, ft. lbs ................................. 1
Spark plug socket, 5/8", 1/2" drive............................... 1
Plug gauge, wire type.................................................. 1
Anti-seize compound................................................ AR
Remove and inspect the spark plugs per Periodic Ser-
vice Schedule in Section A. Fouled spark plugs are indi-
cated by a wet, black appearance. This could be caused
by a dirty air filter element or other restrictions in the air
intake system. Incorrectly adjusted valves, spark plug
wires which are in poor condition or poor quality fuel
could also contribute to the problem. Clean and gap to
.030" (.76 mm). If a plug has been burned beyond .035"
(.89 mm) or the porcelain is cracked, it should be
replaced (Ref Fig. 13 on page H-6).
Spark plugs should be properly gapped to .030" (.76 mm)
(NGK ZGR5A or DENSO J16CR-U), given a light coat of
anti-seize compound and tightened to 15 ft. lbs. (20 Nm)
torque.
ENGINE DESCRIPTION
The engine is a four cycle air cooled, V block, twin cylin-
der, overhead valve unit. It incorporates pressure lubrica-
tion, and a replaceable oil filter.
Engine Specifications
Engine model .......................................HONDA GX610
Type .................................... Four cycle, overhead valve
Number of cylinders......................................2 (V block)
Displacement...................................................... 614 cc
Rated horsepower ................................. 18hp (13.4 kw)
Spark plug type ....... NGK ZGR5A or DENSO J16CR-U
Spark plug gap....................................... .030" (.76 mm)
Cooling ....................................................................Fan
Oil Filter .......................................Replaceable, Spin-off
Engine Operation
To understand the operation of a four cycle engine, it is
easiest to consider a single cylinder.
The first cycle (stroke) takes place with the piston moving
down and the intake valve open. Fuel is drawn into the
combustion chamber from the carburetor and through
the intake valve and is known as the intake stroke. As the
piston reaches the bottom (BDC) of its travel and starts to
move upwards, the second cycle begins. The intake
valve closes which seals the combustion chamber since
the exhaust valve is already closed and causes the fuel
air mixture to be compressed as the piston rises. This is
known as the compression stroke. Just before the piston
reaches TDC (Top Dead Center) the spark plug fires
which causes a rapid burning of the air fuel mixture. The
temperature rises rapidly which causes the air fuel mix-
ture to expand. The piston has been carried through TDC
by centrifugal force and is now forced downwards into
the third, or power stroke by the expanding gases. As the
piston reaches BDC it enters the fourth cycle. The
exhaust valve opens and the piston rises forcing burned
gases from the combustion chamber in what is known as
the exhaust stroke. As the piston moves through TDC
and starts down, the first cycle is repeated.
The camshaft is gear driven from the crankshaft. The
ignition timing is controlled by an electrical pulse
received from a magnet mounted on the crankshaft fly-
wheel. The ignition timing is not adjustable.
Fig. 13 Gapping the Spark Plug
.030"
(.76 mm)
Gap
Spark Plug
Summary of Contents for ST 4X4
Page 6: ...Page iv Repair and Service Manual TABLE OF CONTENTS Notes...
Page 10: ...Repair and Service Manual SAFETY INFORMATION Page viii Notes...
Page 12: ...GENERAL INFORMATION ROUTINE MAINTENANCE Page A ii Repair and Service Manual Notes...
Page 24: ...SAFETY Page B ii Repair and Service Manual Notes...
Page 34: ...BODY AND TRUCKBED Page C ii Repair and Service Manual Notes...
Page 50: ...BRAKES Page D ii Repair and Service Manual Notes...
Page 68: ...CONTINUOUSLY VARIABLE TRANSMISSION CVT Page E ii Repair and Service Manual Notes...
Page 74: ...DIRECTION AND DRIVE SELECTOR Page F ii Repair and Service Manual Notes...
Page 80: ...ELECTRICAL Page G ii Repair and Service Manual Notes...
Page 114: ...FRONT SUSPENSION AND STEERING Page J ii Repair and Service Manual Notes...
Page 128: ...FUEL SYSTEM Page K ii Repair and Service Manual Notes...
Page 136: ...PAINT Page L ii Repair and Service Manual Notes...
Page 142: ...REAR AXLE AND SUSPENSION Page M ii Repair and Service Manual Notes...
Page 152: ...SPEED CONTROL Page N ii Repair and Service Manual Notes...
Page 160: ...TROUBLESHOOTING Page P ii Repair and Service Manual Notes...
Page 168: ...WHEELS AND TIRES Page R ii Repair and Service Manual Notes...
Page 174: ...GENERAL SPECIFICATIONS Page S ii Repair and Service Manual Notes...
Page 180: ...LIMITED WARRANTY Page T ii Repair and Service Manual Notes...
Page 182: ...Page T 2 Repair and Service Manual LIMITED WARRANTY Notes...