Yamaha MX250 - Checking the Rocker Arm; Checking the Push Rod; Checking the Cylinder Head

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ENGINE
CYLINDER HEAD COVER, CYLINDER HEAD
CHECKING THE ROCKER ARM
1.
Check:
• Rocker arm
• Wear/damage/cracks  Replace.
CHECKING THE PUSH ROD
1.
Check:
• Push rod runout
Out of specifications  Replace.
CHECKING THE CYLINDER HEAD
1.
Check:
• Cylinder head combustion chamber
Check the combustion chamber for carbon depos-
its.
Any carbon deposits  Eliminate.
TIP
Be sure not to damage the contact surface of the cylinder.
2.
Check:
• Cylinder head
Cracks/damage around the hole of spark plug 
Replace.
3.
Measure:
• Cylinder head warpage
TIP
Measure the warpage on the contact surface of the cylin-
der head at six points using the straight edge and thick-
ness gauge.
Out of specifications  Resurface or replace.
Runout limit:
0.15 mm (0.0059 in)
Warpage limit:
0.05 mm (0.002 in)