Honda Crf 250 M Manual

							Servicing Your Honda57
Valve Clearance
CamShaft Removal
1. Record the intake valve clearance and exhaust
valve clearance.2. Remove the cam chain tensioner lifter cover
bolt (1) and sealing washer (2).
(1) cam chain tensioner lifter cover bolt
(2) sealing washer
3. Make a tensioner shaft stopper tool (3) out of
a thin piece of steel (0.8 mm thick) using the
diagram.
4. Turn the tensioner shaft clockwise with the
stopper tool (3) until it stops, in order to
retract the tensioner fully.
Then insert the stopper tool fully to hold the
stopper in the fully retracted position.
(3)  stopper tool
(2)
(1)
12.0 mm 7.0 mm
8.5 mm3.5 mm (3)
(3)
(3)
(cont’d) 
						

							Valve Clearance
58Servicing Your Honda
8. Remove the shims (8).
(8) shims
(8)
5. Remove the camshaft holder bolts (4) and
camshaft holders (5).
Loosen the camshaft holder bolts in a criss-cross
pattern in 2 or 3 steps.
6. Remove the camshaft (6), and then attach a
piece of wire to the cam chain to prevent it
from falling into the crankcase.
Be careful to not let the set rings of the camshaft
holders fall into the crankcase.
(4) camshaft holder bolts (6) camshaft
(5) camshaft holders
7. Remove the valve lifters (7).
Position the removed intake valve lifters and
shims to indicate their location such as intake or
exhaust, right or left.
Do not let the valve lifters and shims fall into the
crankcase.
NOTICE
(7) valve lifters
(6)
(4)(5)
(4)
(7) 
						

							Servicing Your Honda59
Valve Clearance
Shim Selection
1. Clean the valve shim contact area in the valve
lifter (1) with compressed air.
(1)  valve lifter
2. Measure the shim thickness and record it.
Seventy-three different thickness shims (2) are
available from the thinnest (1.200 mm
thickness) shim to the thickest (3.000 mm
thickness) in intervals of 0.025 mm.3. Calculate the new shim thickness using the
equation below.
A = (B – C) + D
A: New shim thickness
B: Recorded valve clearance
C: Specified valve clearance
D: Old shim thickness
•Make sure of the correct shim thickness by
measuring the shim with the micrometer.
•Reface the intake valve seat if carbon deposits
result in a calculated dimension of over 2.450
mm.
Reface the exhaust valve seat if carbon
deposits result in a calculated dimension of
over 3.000 mm.
(1)
(2)
(2) shim 
						

							Valve Clearance
60Servicing Your Honda
5. Place the cam sprocket (7) and align the
timing mark (8) on the cam sprocket with the
surface of the cylinder head (9).
Install the cam chain over the sprocket
without rotating the sprocket.
(4) primary drive gear lock bolt
(5) “punch” mark
(6) index mark(7) cam sprocket
(8) timing mark
(9) surface of the cylinder head
(4)(5)(6)
(8)(7)
(9)
(8)
Camshaft Installation
1. Install the newly selected shims (1) on the
valve retainers (2).
Do not let the shims fall into the crankcase.
NOTICE
(1) shims             (2) valve retainers
2. Apply molybdenum disulfide oil (a mixture of
1/2 engine oil and 1/2 molybdenum disulfide
grease (containing more than 3%
molybdenum disulfide additive)) to the
camshaft and outer surface of the each the
valve lifters (3).
3. Install the valve lifters and camshaft into the
camshaft holder assembly.
(3) valve lifters
4. Rotate the primary drive gear lock bolt (4)
(crankshaft) clockwise and align the “punch”
mark (5) with the index mark (6).
(2)
(2)
(1)
(3) 
						

							Servicing Your Honda61
Valve Clearance
6. Apply grease to the set rings and install it
onto the camshaft holders (10).
Install the cam shaft holders onto the cylinder
head with the intake cam lobes (12) facing up
as illustrated below.
Apply the oil to the camshaft holder bolt
threads and seating surface.
Tighten the camshaft holder bolts (11) to the
specified torque:
12 lbf·ft (16 N·m, 1.6 kgf·m)
Tighten the camshaft holder bolts in a criss-cross
pattern in 2 or 3 steps.
(10) camshaft holders
(11) camshaft holder bolts
(12) intake cam lobes
10. Insert the feeler gauge (16) between the intake
valve lifter and cam lobe.
If the feeler gauge cannot be inserted, the
shim is caught between the valve lifter and
the valve retainer. Remove the camshaft
holders, place the shim correctly, and reinstall
the camshaft holders.
Valve Clearances:
IN:  0.005 ± 0.001 in (0.12 ± 0.03 mm)
EX: 0.011 ± 0.001 in (0.28 ± 0.03 mm)
(16) feeler gauge
(11)
(11)
(10)
(12)
(16)(16)
7. Remove the stopper tool (13) from the cam
chain tensioner lifter.
(13)
(13) stopper tool
8. Install the new sealing washer (14) and cam
chain tensioner lifter cover bolt (15).
(14) sealing washer
(15) cam chain tensioner lifter cover bolt
(14)
(15)
(cont’d) 9. Rotate the camshaft by rotating the crankshaft
clockwise several times. 
						

							62Servicing Your Honda
Valve Clearance
11. Install the spark plug (17) (page 54).
(17) spark plug
12.Coat a new O-ring (18) with grease and install
it onto the crankshaft hole cap (19).
Apply grease to the crankshaft hole cap
threads.
Install and tighten the crankshaft hole cap to
the specified torque:
11 lbf·ft (15 N·m, 1.5 kgf·m)
(18) O-ring
(19) crankshaft hole cap
Cylinder Head Cover Installation
1. Remove the spark plug hole packing (1) from
the cylinder head cover.
Install the spark plug hole packing to the
spark plug hole (2). 
(1) spark plug hole packing
(2) spark plug hole
2. Install the cylinder head cover packing (3)
into the groove of the cylinder head cover (4).
(3) cylinder head cover packing
(4) cylinder head cover
3. Tighten the cylinder head cover (5) and
cylinder head cover  bolts (6) to the specified
torque:
7 lbf·ft (10 N·m, 1.0 kgf·m)
(5) cylinder head cover
(6) cylinder head cover bolts
4. Connect the spark plug cap (7) and breather
tube (8).
(7) spark plug cap
(8) breather tube
5. Install the fuel tank and the seat (page 31).
(18)
(19)
(17)
(2)
(1)
(4)
(3)
(5)(6)
(7)
(8) 
						

							Servicing Your Honda63
Piston/Piston Rings/Piston Pin
Cylinder Head Removal
1. Clean the area above the engine before
disassembly to prevent dirt falling into the
engine.
2. Drain the engine oil (page 37).
3. Drain the radiator coolant after cooling the
motorcycle (page 42).
4. Remove the seat (page 29). and fuel tank
(page 30).
5. Remove the muffler and subframe (page 32).
6. Remove the carburetor (page 117).
7. Remove the exhaust pipe joint nuts (1),
exhaust pipe (2) and exhaust pipe gasket (3)
(page 88).
(1) exhaust pipe joint nuts
(2) exhaust pipe
(3) exhaust pipe gasket
8. Disconnect the spark plug cap (4).
9. Remove any dirt around the spark plug base.
(4) spark plug cap
(5) spark plug
11. Position the piston at top dead center on the
compression stroke (page 55).
Remove the cam shaft holders (page 57).
12.Loosen the radiator hose clamp (6) and
disconnect the radiator hose (7).
(6) radiator hose clamp
(7) radiator hose
(2)
(1)
(3)
(4)
(5)
(7)(6)
(cont’d) 10. Remove the cylinder head cover (page 55).
Remove the spark plug (5). 
						

							64Servicing Your Honda
Piston/Piston Rings/Piston Pin
13.Remove the engine hanger nuts (8) and engine
hanger plates (9).
(8) engine hanger nuts
(9) engine hanger plates
14.Remove the cylinder head bolts (10).
15.Loosen the cylinder bolt (11).
(10) cylinder head bolts
(11) cylinder bolt
Loosen the nuts in a criss-cross pattern in 2 or 3
steps.
Do not let the nuts, washers, valve lifters, shims,
and cam chain fall into the crankcase.
16.Remove the cylinder head nuts, washers (12)
and cylinder head (13).
NOTICE
(12) cylinder head nuts/washers
(13) cylinder head
17.Remove the dowel pins (14), cylinder head
gasket (15) and cam chain guide (16).
Do not let the dowel pins and cam chain fall into
the crankcase.
NOTICE
(14) dowel pins (16) cam chain guide
(15) cylinder head gasket
(8)
(9)
(10)
(11)
(13)(12)
(14)(15)
(16) 
						

							Servicing Your Honda65
Piston/Piston Rings/Piston Pin
Cylinder Removal
1. Remove the cylinder bolt (1) and cylinder (2).
Do not let the cam chain fall into the crankcase.
Do not pry on or strike the cylinder.
NOTICE
(1) cylinder bolt
(2) cylinder
2. Remove the dowel pins (3) and cylinder
gasket (4).
Do not let the dowel pins fall into the crankcase.
NOTICE
(3) dowel pins
(4) cylinder gasket
Piston Removal
1. Place clean shop towels in the crankcase to
keep the piston pin clips, or other parts, from
falling into the crankcase.
2. Remove the piston pin clips (1) using a pair of
needle-nose pliers.
3. Press the piston pin (2) out of the piston (3),
and remove the piston.
Do not damage the piston.
Always support the piston when pressing out the pin.
Do not let the clips fall into the crankcase.
Under racing conditions, the piston and rings
should be replaced after 15.0 hours of running.
Replace the piston pin after 30.0 hours of running.
NOTICE
(1) piston pin clip (3) piston
(2) piston pin (4) piston rings
4. Spread each piston rings (4) and remove by
lifting it up at a point just opposite the gap.
Do not damage the piston ring by spreading the
ends too far.
NOTICE
(2)
(1)
(4)
(3)
(3)
(2)(1)
(4) 
						

							66Servicing Your Honda
Piston/Piston Rings/Piston Pin
Piston Ring Installation 
1. Clean the piston ring groove 
2. Apply engine oil to the piston rings and install
them.
Do not damage the piston ring by spreading the
ends too far.
Do not damage the piston during piston ring
installation.
•  To install the oil ring, install the spacer first,
then install the side rails.
•Install the top ring on the piston with the
marking side facing up.
3. After installing the rings they should rotate
freely, without sticking.
Space the ring end gaps 180 degrees apart
between top ring and upper side rail.
Space the ring end gaps 90 degrees apart
between upper side rail, spacer and lower side
rail.
NOTICE
top ring
oil ring
mark
top ring
oil 
ring side rail
side rail spacerCamShaft Holders/Cylinder
Head/Cylinder/Piston/Piston Pin/Piston
Ring Inspection
We recommend you consult the Service Manual
or your authorized Honda dealer for correct
Service Limit measurements.