Yamaha MTN850-A 2017, Service Manual, Page: 120 / 560

PERIODIC MAINTENANCE
3-10
dard. Otherwise, the engine may run roughly
at idle and the throttle bodies may not oper-
ate properly.
TIP
• Turn the bypass air screw using the carburetor
angle driver.
•
After each step, rev the engine two or three
times, each time for less than a second, and
check the synchronization again.
• If a bypass air screw was removed, turn the
screw in fully and be sure to synchronize the
throttle bodies.
•
If the throttle body synchronization can not be
adjusted using the bypass air screw, clean or
replace the throttle bodies.
• The difference in vacuum pressure between
the throttle bodies should not exceed 1.33 kPa
(10 mmHg).
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2. Stop the engine and remove the measuring
equipment.
3. Install:
•
Caps
4. Install:
•
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.
5. Adjust:
•
Throttle grip free play
Refer to “CHECKING THE THROTTLE
GRIP” on page 3-29.
EAS30798
CHECKING THE THROTTLE BODY JOINTS
1. Remove:
• Throttle bodies
Refer to “THROTTLE BODIES” on page 7-5.
2. Check:
• Throttle body joints “1”
Cracks/damage

Replace.
3. Install:
•
Throttle bodies
Refer to “THROTTLE BODIES” on page 7-5.
EAS31922
CHECKING THE CANISTER
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.
2. Check:
• Canister
•
Canister purge hose
• Fuel tank breather hose
•
Canister breather hose
Cracks/damage

Replace.
3. Install:
• Fuel tank
Refer to “FUEL TANK” on page 7-1.
Carburetor angle driver 2
90890-03173
1
Throttle grip free play
3.0–5.0 mm (0.12–0.20 in)
1