Valve Clearance Adjustment - Yamaha MA190 Service Manual

3-6 Valve clearance adjustment

Keep the clearance between engine valve rod end and driving parts for avoiding heat expanding
and cold shrinking to effect engine performance. If the valve is too big, it can result in exhausting
unsmooth, effecting engine performance and increasing engine noise (valve abnormal), if the valve
is too small, the valve will close untight to make the engine operating abnormal and drain valve
operating face burn. After operating one year or 300h, check and adjust the valve.
1. Dismount the spark plug cap, spark plug, cylinder head cover bolt, cylinder head cover and
gasket in order.
NOTICE
After the cylinder head cover is removed, engine oil may flow. Be sure to wipe up any
flowed oil.
Bolt M6 × 12
Bolt M6 × 80
Screwdriver
Stud M6 × 109
Bolt
Head cover
Feeler
3-6 Valve clearance adjustment
Spark plug Cylinder head gasket
Cylinder head assy.
Cover gasket
2. Lightly pull the starting rope and set the
piston at top dead center of the compres-
sion stroke (insert screwdriver into the
hole of the spark plug hole to check the
height of piston.)
3. Measure the valve clearance: Insert the
feeler into the clearance to measure
clearance.
Valve clearance:
Adjust if the valve clearance is out of the
service limit.
NOTICE
Measure the valve clearance in the cold
the engine state.
17
Dowel 10 × 14
Stud M6 × 105
IN: 0.10–0.15 mm
EX: 0.15–0.20 mm