Checking The Cylinder Head - Yamaha YBR250 2007 Service Manual

CYLINDER HEAD

CHECKING THE CYLINDER HEAD

1. Dispose:
• combustion chambers carbon deposits (with
a round scraper)
NOTE:
Do not use a sharpen tool, to prevent damage or
scratches in:
• spark plug threads
• valve seats
2. Check:
• cylinder head
Damage/Scratches --> Replace.
3. Measure:
• cylinder head runout
Out of specification --> Remove the cylinder
head.
Maximum runout
0.03 mm (0.001 in)
a. Place a ruler 1 and a thickness gauge 2
along the cylinder head.
b. Measure the runout.
c. When the limit is exceed, rebore the cylinder.
d. With a thin sandpaper (400 to 600 grainy) is
applied to the cylinder head surface, carry out
the grinding, making movements following the
"8" shape.
NOTE:
To ensure a level surface, spin the cylinder head
several times.
5-10
ENG