Linhai ARCHON 400, Service Manual

Page: 102 / 218

CHAPTER 3 ENGINE
BUCK 450 SERVICE MANUAL 20.0
ACTION REASON
DO: Cleaning a spark plug could be done as follow:
1- Wipe all spark plug surfaces clean….remove oil,
water, dirt and moist residues.
2- If the firing end of spark plug has oily or wet
deposit, brush the spark plug in an approved,
non-flammable and non-toxic solvent. Then dry the
spark plug thoroughly with compressed air.
3- Use a propane torch to dry wet-fuel fouled plugs.
Allow the torch flame to enter up the center
electrode insulator. Allow plug to cool down.
4- If the spark plug threads have carbon & scale
deposits, clean with wire brush, taking care not to
injure the electrode or the insulator tip.
Cleaning a spark plug will reduce the voltage required
for an electrical arc(spark) across the electrodes.
Cleaning & re-gapping will not restore a used spark
plug to a new condition. It may be more economical
and efficient to replace used spark plugs with new
plugs instead of cleaning.
Sooted plugs should be replaced.
Do not cool by using water or any liquid.
Clean threads permit easier installation and proper
seating which will maximize transfer heat away from
the plug.
DO: Regap spark plugs to the exact measurement
specified by the engine manufacturer to keep the
best fuel economy and proper engine performance:
1- Use round wire-type gauge for an accurate
measure of gap on all used spark plugs.
2- When gapping a spark plug only the side
electrode is moved. The center electrode must not
be moved.
Too wide a gap could cause the plug to misfire (higher
required ignition voltage).
Too narrow of a gap could affect idle stability.
A flat gauge can’t accurately measure the spark plug
on used plugs.
DO: When replacing spark plugs with new ones,
always use equivalent plugs with same heat range,
thread, size, etc….
Higher heat range plug (hotter plug) could lead to
pre-ignition & possible piston damage.
Lower heat range (colder plug) could lead to cold
fouling & emission problem.
DO: For installing spark plugs follow the following
steps:
1- Make sure the cylinder head threads and spark
plug threads are clean. Make sure the spark plug
thread is free of dings and burrs. If necessary, use
a thread chaser and seat cleaning tool.
2- Make sure the spark plug gasket seat is clean,
and then thread the gasket to fit flush against the
gasket seat. Tapered seat plugs do not require
gaskets.
3- Screw the spark plugs finger-tight into the
cylinder head. Then, use a torque wrench to tighten
spark plugs following manufacturer’s
recommendation.
Torque is different for various plug type & cylinder
head material.
If the thread is damage, it prevents a good heat
transform from the shell to the cylinder head.
Do not use any type of anti-seize compound on spark
plug threads. Doing this will decrease the amount of
friction between the threads. The result of the lowered
friction is that when the spark plug is torqued to the
proper specification, the spark plug is turned too far
into the cylinder head. This increases the likelihood of
pulling or stripping the threads in the cylinder head.
Over tightening of a spark plug can cause stretching of
the spark plug shell and could allow blowby to pass
thru the gasket seal between the shell and insulator.
Over-tightening also results in extremely difficult
removal.
CHAPTER 3 ENGINE PAGE. 3- 77