Yamaha MZ250 Service Manual page 112

ENGINE SPEED DOES NOT INCREASE
Check the spark plug for dirt and check the spark
plug gap.
GOOD
Check the air filter element for dirt.
GOOD
Check the compression pressure.
GOOD
Check if the main passages, such as the main jet
in the carburetor, are clogged.
GOOD
Check if there is air suction from the carburetor
joint, gasket, or throttle shaft.
GOOD
DIRTY OR OUT OF
SPECIFICATION
DIRTY
TOO HIGH
TOO LOW
Measure the valve clearance.
GOOD
Check the valve face and valve seat for wear.
GOOD
Check if the marks on the crankshaft and cam-
shaft are aligned.
GOOD
Check if there is seizure, wear, or damage on the
piston, piston ring, or cylinder.
GOOD
CLOGGED
NOT GOOD
6-5
ENGINE
Clean, adjust, or replace.
Decarbonize the com-
bustion chamber if there
is carbon deposits.
OUT OF
SPECIFICATION
WORN
NOT GOOD
SEIZURE OR WORN
9 Tighten the carburetor
nuts securely.
9 Replace the carburetor
joint or gasket with a
new one.
TRBL
Clean.
Adjust.
Resurface or
replace.
Correct.
Rebore or
replace.
Clean the parts.