B
78
Repair and Service Manual
ENGINE
Read all of SAFETY and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
699322
FOUR CYCLE ENGINE
Engine Specifications
Engine Model .................................................. FJ400-D
Type.................................. Four Cycle, Overhead Valve
Number Of Cylinders ...................................................1
Displacement...................................................... 401 cc
Rated Horsepower................................................13 hp
Spark Plug Type .....................................NGK BPR2ES
Spark Plug Gap ...................028" - .031" (.70 - .80 mm)
Cooling ............................................. Forced Air Cooled
Oil Filter ......................... Cartridge Type Full Flow Filter
Oil Pump.......................... Positive Displacement Pump
Engine Description
The engine is an air cooled, 4-stroke, overhead valve,
single cylinder gasoline engine. It incorporates a pressure
fed lubrication positive displacement oil pump with a car-
tridge type full flow oil filter and a counter rotating balance
shaft.
CYLINDER HEAD
Compression Measurement
Tool List
Qty.
Ratchet ........................................................................ 1
Spark Plug Socket .......................................................1
Extension 6" ................................................................1
Compression Gauge & Adapter (20 kgf/cm
2
)
................
1
Before measuring compression, do the following:
•
Be sure the battery is fully charged.
•
Thoroughly warm up the engine so that engine oil
between the piston and cylinder wall will help seal
compression as it does during normal running.
•
Stop the engine.
Disconnect the spark plug cap (3) and remove the spark
plug (4) keeping the engine throttle fully open.
Attach the compression gauge (1) to the adapter (2) and
insert firmly into the plug hole.
Fig. 16 Compression Gauge
Place the spark plug cap (3) on the removed spark plug
(4) and ground the spark plug to the engine.
To prevent possibility of personal
injury or fire, do not ground the
spark plug in proximity to the plug
hole. Keep the plug as far away as possible from the
plug hole. Fuel drawn into the cylinder will be
expelled through the spark plug opening and could
be ignited by the ignition system or another source,
resulting in a fire.
Using the starter motor, turn the engine over with the
throttle fully open until the compression gauge stops ris-
ing.
Cylinder Compression should be between 9 - 11 kgf/cm
2
(128-156 psi).
If the compression is higher than 9 kgf/cm
2
(128 psi) the
piston rings, cylinder and valves are probably in good
condition.
If the compression is over 11 kgf/cm
2
(156 psi), check the
following:
1. Carbon build-up on the piston crown and cylinder
head - clean off any carbon on the piston crown and
cylinder head.
2. Cylinder head gasket - use only the proper gasket.
The use of a gasket of incorrect thickness will change
the compression.
3. Valve guides and piston rings - rapid carbon accumu-
lation in the combustion chamber may be caused by
worn valve guides and/or worn piston oil rings. This
may be indicated by white exhaust smoke.
If cylinder compression is lower than 9 kgf/cm
2
(128 psi),
check the following:
1. Gas leakage around the cylinder head - replace the
damaged head gasket and check the cylinder head for
warp.
1
2
3
4
