Checking The Spark Plugs; Adjusting The Valve Clearance - Yamaha MTN850-A 2017 Service Manual

EAS30620

CHECKING THE SPARK PLUGS

The following procedure applies to all of the
spark plugs.
1. Remove:
• Air scoop
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Rider seat
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Fuel tank cover
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Fuel tank
Refer to "FUEL TANK" on page 7-1.
• Air filter case
Refer to "GENERAL CHASSIS (2)" on page
4-7.
• Air cut-off valve
Refer to "AIR INDUCTION SYSTEM" on
page 7-15.
2. Remove:
• Ignition coils
• Spark plugs
ECA13320
NOTICE
Before removing the spark plugs, blow away
any dirt accumulated in the spark plug wells
with compressed air to prevent it from falling
into the cylinders.
3. Check:
• Spark plug type
Incorrect  Change.
Manufacturer/model
NGK/CPR9EA9
4. Check:
• Electrode "1"
Damage/wear  Replace the spark plug.
• Insulator "2"
Abnormal color  Replace the spark plug.
Normal color is medium-to-light tan.
5. Clean:
• Spark plug
(with a spark plug cleaner or wire brush)
6. Measure:
• Spark plug gap "a"
(with a wire thickness gauge)
Out of specification  Regap.
Spark plug gap
0.8–0.9 mm (0.031–0.035 in)
PERIODIC MAINTENANCE
7. Install:
• Spark plugs
• Ignition coils
Spark plug
13 N·m (1.3 kgf·m, 9.4 lb·ft)
TIP
Before installing the spark plug, clean the spark
plug and gasket surface.
8. Install:
• Air cut-off valve
Refer to "AIR INDUCTION SYSTEM" on
page 7-15.
• Air filter case
Refer to "GENERAL CHASSIS (2)" on page
4-7.
• Fuel tank
Refer to "FUEL TANK" on page 7-1.
• Fuel tank cover
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Rider seat
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Air scoop
Refer to "GENERAL CHASSIS (1)" on page
4-1.
EAS30622

ADJUSTING THE VALVE CLEARANCE

The following procedure applies to all of the
valves.
TIP
Valve clearance adjustment should be made on
a cold engine, at room temperature.
1. Remove:
• Air scoop
Refer to "GENERAL CHASSIS (1)" on page
4-1.
• Rider seat
Refer to "GENERAL CHASSIS (1)" on page
4-1.
3-5