Yamaha MX775 - ENGINE SPEED DOES NOT INCREASE

6-4
1
2
3
4
5
6
7
8
9
10
TROUBLESHOOTING
OTHER TROUBLES
ENGINE SPEED DOES NOT INCREASE
No. Checking steps Possible remedy
1
Check the spark plugs for dirt and check the spark plug
gap.
Clean, adjust, or replace the spark
plugs.
2 Check the air filter element for dirt. Replace the air filter element.
3 Check spark arrester, muffler and air filter.
Clean or replace spark arrester, muffler
and air filter.
4
Check the valve clearance.
(Refer to “ADJUSTING THE VALVE CLEARANCE” on
page 2-9)
Adjust the valve clearance.
5
Check the compression pressure.
(Refer to “MEASURING THE COMPRESSION PRES-
SURE” on page 3-1)
Too high:
Decarbonize the combustion chamber if
there is carbon deposits.
Too low:
Next checking steps.
6
Check governor setting.
(Refer to “INSTALLING THE THROTTLE BODY ASSEM-
BLY” on page 4-7)
Adjust the governor.
7
Check the valve face and valve seat for wear.
(Refer to “VALVES” on page 3-27)
Resurface or replace the valve face and
valve seat.
8
Check if the marks on the crankshaft and camshaft are
aligned.
(Refer to “INSTALLING THE VALVE LIFTERS AND CAM-
SHAFT” on page 3-45)
Correct.
9
Check if there is seizure, wear, or damage on the piston,
piston ring, or cylinder.
(Refer to “PISTONS, CAMSHAFT, CRANKCASE, AND
CRANKSHAFT” on page 3-38)
Rebore or replace.
10
Check if the main passages, such as the throttle body
assembly, are clogged.
Clean the parts.
11
Check if there is air suction from the throttle body assembly
joint, gasket, or throttle shaft.
• Tighten the throttle body assembly
nuts securely.
• Replace the throttle body assembly
joint or gasket with a new one.