ENGINE
Read all of SAFETY and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
53
A fouled spark plug is indicated by an electrode with a
wet, black appearance. A fouled plug can be caused by:
• Dirty air filter element
• Restrictions in the air intake system
• Incorrect valve adjustment
• Spark plug wire in poor condition
• Poor quality fuel
Use care not to over-tighten the plug. Over-tighten-
ing can cause damage to the aluminum cylinder
head threads.
Remove and inspect the spark plug at intervals indi-
cated in the Periodic Service Schedule. Spark plug
should be properly gapped.
CYLINDER HEAD
Compression Leak Down Test
Tool List Qty.
Ratchet. .......................................................................1
Spark Plug Socket .......................................................1
Extension, 6" ...............................................................1
Leak Down Gauge with Plug Adapters........................ 1
Air Compressor ........................................................... 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 and remove the spark plug
keeping the engine throttle and the choke valve fully
open.
1. Remove the oil dipstick/fill cap and the spark plug.
2. Rotate the crankshaft to position the cylinder to be
tested 10°-15° past TDC so that the exhaust valve is
closed.
3. Lock the crankshaft in position with a strap wrench
wrapped around the drive clutch.
4. Select the spark plug adapter that fits the spark plug
hole.
5. Connect the leak down gauge.
6. Turn the regulator knob counterclockwise to zero out
the incoming pressure.
7. Connect the compressed air hose and turn the regu-
lator knob clockwise to pressurize the cylinder.
8. Compare the reading of the compression gauge with
the setting on the regulator to obtain the leak down
percentage.
9. Repeat the process for the next cylinder.
Record the leakage percentage for each cylinder. Maxi-
mum leak down should run no more than 10 - 15%.
Listen to see if air is escaping through the carburetor, the
oil filler or the exhaust. Air leaking through the carburetor
or throttle body indicates poor sealing of the intake valve.
Leaking from the tail pipe indicates poor exhaust valve
sealing. Air leaking around the outside of the head gasket
flange indicates a blown head gasket.
Rocker Cover Removal
Tool List Qty.
Ratchet ........................................................................1
Extension 6”.................................................................1
Socket, 10 mm.............................................................1
1. Remove the four bolts (5) securing the rocker cover.
2. Remove the rocker cover (6) and the gasket.
Figure 17 Rocker Cover
Valve Clearance Inspection
Tool List Qty.
Allen Bit, 3 mm.............................................................1
Ratchet ........................................................................1
Extension, 6”................................................................1
Feeler Gauge...............................................................1
Wrench, 14 mm ...........................................................1
Torque Wrench, in. lbs. ...............................................1
Valve clearance must be checked when the engine is
cold (at room temperature).
With the rocker cover removed, place the piston at TDC
of the compression stroke by turning the crankshaft in its
rotational direction.
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