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...

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...

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...

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...

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)...

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...

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...

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)....

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...

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...