Cylinder Head/Cyiinder/Piston - Honda CB250N Shop Manual

7.
Cylinder Head/Cyiinder/Piston
Service Information 7-1 Camshaft
Installation
7
•6
Troubleshooting 7-1
Cylinder
Head
Removal/Installation 7
10
Camshaft Removal 7-2
Cylinder
Head
Disassembly/Assembly
7-
11
.
Camshaft
Holder
Disassembly/Assembly 7-5
Cylinder, Piston Removal/Installation
7- 12
Service Information
Camshaft
service
can be done with the engine
in
the
frame.-
Camshaft
lubricating
oil is
fed
through
oil
passages
in
the
cylinder head. Clean the
oil
passages before assembling
the
cylinder head.
Clean
all
disassembled parts with clean solvent and dry thern by blowing
them
off
with
compressed
air
before
inspection.
Before reassembly,
lubricate
the camshaft bushings and
cam
lobes with a
molybdenum
solution (half
engine
oil
and
half
molybdenum
grease).
.,
When
disassembling,
mark and
store
the disassembled
parts to ensure that they are reinstalled
in their
proper
locations.
Troubleshooting
Engine top-end problems
usually affect
engine performance/These can be diagnosed by
a
compression
or
leak-down
test,
or
by
tracing noises
to
the top-end with
a
sounding rod
or stethoscope.':
'
If
performance
is
poor
at
low speeds, check
for
white
smoke
in
the crankcase
breather tube.
If
the
tube
is
smoky, check
for
a seized piston
ring.
Compression
Too
Low, Hard
Starting
Or Poor Performance
At
Low
Speed
-
Valves
—
Incorrect valve adjustment
—
Burned
or bent valves
—
Incorrect valve timing
—
Broken valve
spring
—
Uneven
valve seating
-
Cylinder head
—
Leaking or
damaged
head gasket
—
Warped
or
cracked
cylinder
head
Cylinder, piston
—
Leaking
cylinder
head gasket
—
Loose
spark plugs
—
Worn,
stuck
or
broken piston
rings
— Worn
or
damaged
cylinder
and
piston
Compression Too
High,
Overheating
Or Knocking
•
Excessive carbon
built-up
in cylinder
head
or
on
top of
piston
Excessive
Smoke
•
Cylinder
head
—
Worn
valve
stem
or
valve guide
—
Damaged stem
seal
•
Cylinder, piston
—
Worn
cylinder, piston,
or
piston rings
—
Improper
installation of piston rings
—
Scored
or
scratched
piston or cylinder wall
Excessive Noise
•
Cylinder
head
—
Incorrect
valve
adjustment
—
Sticking valve
or
broken valve spring
—
Damaged
or
worn
camshaft
—
Loose
or
worn
cam
chain
—
Worn
or
damaged
cam
chain
—
Worn
or
damaged cam
chain tensioner
—
Worn cam
sprocket teeth
—
Worn
rocker
arm
and/or shaft
•
Cylinder, piston.
—
Worn
cylinder and piston
—
Worn
piston pin
and
piston pin hole
Rough
idle
•
Low
cylinder
compression
"7_1