Valve Guide Removal
• Remove:
Valve (see Valve Removal)
Oil Seal Spring Seat
• Heat the area around the valve guide to 120 150°C (248
302°F), and hammer lightly on the valve guide arbor [A]
to
remove the guide from the top of the head.
Special Tool - Valve Guide Arbor, 4.5: 57001-1331
Valve Guide Installation
•
Apply engine oil to the valve guide outer surface before
installation.
• Heat the area around the valve guide hole to about 120
150°C (248 302°F).
• Drive the valve guide in from the top of the head using the valve guide arbor. The flange stops the guide from going
in too far.
Special Tool - Valve Guide Arbor, 4.5: 57001-1331
• Wait until the cylinder head cools down and then ream the valve guide with the valve guide reamer [A] even if the old
guide is reused.
○Turn the reamer in a clockwise direction until the reamer
turns freely in the guide. Never turn the reamer counter-
clockwise or it will be dulled.
○Once the guides are reamed they must be cleaned thor-
oughly.
Special Tool - Valve Guide Reamer, 4.5: 57001-1333
Valve-to-Guide Clearance Measurement (Wobble Method)
If a small bore gauge is not available, inspect the valve guide wear by measuring the valve to valve guide clearance with the wobble method as indicated below.
• Insert a new valve [A] into the guide [B] and set a dial
gauge against the stem perpendicular to it as close as
possible to the cylinder head mating surface.
• Move the stem back and forth [C] to measure valve/valve guide clearance.
• Repeat the measurement in a direction at a right angle to
the first.
If the reading exceeds the service limit, replace the guide.
NOTE
○The reading is not actual valve/valve guide clearance
because the measuring point is above the guide.
Valve/Valve Guide Clearance (Wobble Method) Standard:
Exhaust 0.07 0.14 mm (0.0028 0.0055 in.)
Inlet 0.02 0.08 mm (0.0008 0.0032 in.)
Service Limit:
Exhaust 0.27 mm (0.0106 in.)
Inlet 0.22 mm (0.0087 in.)
Valve
Seat Inspection
• Remove the valve (see Valve Removal).
• Check the valve seating surface [A] between the valve [B]
and valve seat [C].
○Measure the outside diameter [D] of the seating pattern
on the valve seat.
If the outside diameter is too large or too small, repair the seat (see Valve Seat Repair).
Valve Seating Surface Outside Diameter Standard:
Exhaust 27.6 27.8 mm (1.087 1.094 in.)
Inlet 32.6 32.8 mm (1.283 1.291 in.)
○Measure the seat width [E] of the portion where there is no build-up carbon (white portion) of the valve seat with a vernier caliper.
Good [F]
If the width is too wide [G], too narrow [H] or uneven [J], repair the seat (see Valve Seat Repair).
Valve Seating Surface Width Standard:
Exhaust 0.5 1.0 mm (0.020 0.039 in.)
Inlet 0.5 1.0 mm (0.020 0.039 in.)
Valve
Seat Repair
• Repair the valve seat with the valve seat cutters [A].
Special Tools - Valve Seat Cutter Holder Bar [C]: 57001-1128
Valve Seat Cutter Holder, 4.5 [B]: 57001-1330
For Exhaust Valve Seat
Valve Seat Cutter, 45° - 30: 57001-1187
Valve Seat Cutter, 32° - 30: 57001-1120
Valve Seat Cutter, 60° - 30: 57001-1123
For Inlet Valve Seat
Valve Seat Cutter, 45° - 35: 57001-1116
Valve Seat Cutter, 32° - 35: 57001-1121
Valve Seat Cutter, 55° - 35: 57001-1247
If the manufacturer’s instructions are not available, use the following procedure.
Seat Cutter Operation Care
This valve seat cutter is developed to grind the valve for repair. Therefore the cutter must not be used for other purposes than seat repair.
Do not drop or shock the valve seat cutter, or the dia- mond particles may fall off.
Do not fail to apply engine oil to the valve seat cutter before grinding the seat surface. Also wash off ground particles sticking to the cutter with washing oil.
NOTE
○Do not use a wire brush to remove the metal particles
from the cutter. It will take off the diamond particles.
Setting the valve seat cutter holder in position, operate the cutter in one hand. Do not apply too much force to the diamond portion.
NOTE
○Prior to grinding, apply engine oil to the cutter and dur-
ing the operation, wash off any ground particles sticking
to the cutter with washing oil.
After use, wash it with washing oil and apply thin layer of engine oil before storing.
Marks
Stamped on the Cutter
The marks stamped on the back of the cutter [A] represent the following.
60° ........................... Cutter angle [B]
37.5 ....................... Outer diameter of cutter [C]
Operating Procedures
• Clean the seat area carefully.
• Coat the seat with machinist’s dye.
• Fit a 45° cutter into the holder and slide it into the valve
guide.
•
Press down lightly on the handle and turn it right or left.
Grind the seating surface only until it is smooth.
•
Measure the outside diameter of the seating surface with
a vernier caliper.
If the outside diameter of the seating surface is too small, repeat the 45° grind until the diameter is within the spec- ified range.
Widened Width [A] of engagement by machining with 45° cutter
Ground Volume [B] by 32° cutter 32° [C]
Correct Width [D]
Ground Volume [E] by 60° or 55° cutter 60° or 55° [F]
•
Measure the outside diameter of the seating surface with
a vernier caliper.
If the outside diameter of the seating surface is too small, repeat the 45° grind [A] until the diameter is within the specified range.
Original Seating Surface [B]
NOTE
○Remove all pittings of flaws from 45° ground surface.
○After grinding with 45° cutter, apply thin coat of machin-
ist’s dye to seating surface. This makes seating surface
distinct and 32° and 60° (or 55°) grinding operation eas- ier.
○When the valve guide is replaced, be sure to grind with
45° cutter for centering and good contact.
If
the outside diameter [A] of the seating surface is too large, make
the 32° grind described below.
If the outside diameter of the seating surface is within the specified range, measure the seat width as described be- low.
• Grind the seat at a 32° angle [B] until the seat outside
diameter is within the specified range.
○To make the 32° grind, fit a 32° cutter into the holder, and
slide it into the valve guide.
○Turn the holder one turn at a time while pressing down
very
lightly. Check the seat after each turn.
○After making the 32° grind, return to the seat outside di- ameter measurement step above.
• To measure the seat width, use a vernier caliper to mea-
sure the width of the 45° angle portion of the seat at sev-
eral places around the seat.
If the seat width is too narrow, repeat the 45° grind until the seat is slightly too wide, and then return to the seat outside diameter measurement step above.
If
the seat
width is
too wide,
make the
60° or
55° [A]
grind described below.
If the seat width is within the specified range, lap the valve to the seat as described below.
• Grind the seat at a 60° or 55° angle until the seat width is
within the specified range.
○To make the 60° or 55° grind, fit 60° or 55° cutter into the
holder, and slide it into the valve guide.
○Turn the holder, while pressing down lightly.
○After making the 60° or 55° grind, return to the seat width
measurement step above.
Correct Width [B]
•
Lap the
valve to
the seat,
once the
seat width
and outside
diameter are within the ranges specified
above.
○Put a little coarse grinding compound on the face of the
valve in a number of places around the valve head.
○Spin the valve against the seat until the grinding com-
pound produces a smooth, matched surface on both the
seat and the valve.
○Repeat the process with a fine grinding compound.
Lapper [A]
Valve Seat [B] Valve [C]
• The seating area should be marked about in the middle
of the valve face.
If the seat area is not in the right place on the valve, check to be sure the valve is the correct part. If it is, it may have been refaced too much; replace it.
• Be sure to remove all grinding compound before assem-
bly.
• When the engine is assembled, be sure to adjust the valve clearance (see Valve Clearance Adjustment in the Peri-
odic Maintenance chapter).
Cylinder Removal
•
Remove:
Cylinder Head (see Cylinder Head Removal)
Front Engine Mounting Bolts (Both Side) [A] (see Engine Removal in the Engine Removal/Installation chapter) Front Engine Brackets (Both Side) [B] (see Engine Re- moval in the Engine Removal/Installation chapter) Cylinder [C]
Cylinder
Installation
NOTE
○If a new cylinder is used, use new piston ring.
• Install the dowel pins [A] and new cylinder gasket [B].
•
The piston ring openings must be positioned as shown in
the figure. The openings of the oil ring steel rails must be
about 30 40° of angle from the opening of the top ring. Top Ring [A]
Second Ring [B]
Oil Ring Steel Rails [C] Oil Ring Expander [D] Hollow [E]
30 40° [F]
•
Apply molybdenum disulfide oil solution to the cylinder bore,
piston rings and piston.
• Prepare two auxiliary head bolts with their head cut.
○Install the two bolts [A] diagonally in the crankcase.
• Position the crankshaft so that all the piston heads are almost level.
• Install the cylinder block.
○Insert the piston rings with your thumbs.
Piston
Removal
• Remove the cylinder (see Cylinder Removal).
• Place a clean cloth under the pistons and remove the pis-
ton pin snap ring [A] from the outside of each piston.
• Remove the piston pins.
Special
Tools - Piston Pin Puller [A]: 57001-1568
Piston Pin Puller Adapter C [D]: 57001-1657
Center Bolt [B] Shall of Piston [C]
• Remove the pistons.
•
Carefully spread the ring opening with your thumbs and then
push up
on the
opposite side
of the
ring [A]
to remove
it.
• Remove the 3-piece oil ring with your thumbs in the same manner.
Piston
Installation
• Install the oil ring expander [A] in the bottom piston ring groove so the ends [B] butt together.
• Install the oil ring steel rails, one above the expander and
one below it.
○Spread the rail with your thumbs, but only enough to fit
the rail over the piston.
○Release the rail into the bottom piston ring groove.
NOTE
○The oil ring rails have no “top” or “bottom”.
•
Do not mix up the top and second ring.
• Install the top ring [A] so that the "R" mark [B] faces up.
• Install the second ring [C] so that the "RN" mark [D] faces
up.
NOTE
○If a new piston is used, use new piston ring.
• Install the piston with its marking hollow facing forward.
• Fit a new piston pin snap ring into the side of the piston
so that the ring opening [A] does not coincide with the slit
[B] of the piston pin hole.
○Apply molybdenum disulfide oil solution to the piston pins
and piston journals.
○When installing the piston pin snap ring, compress it only
enough
to install it and no more.
• Install the cylinder (see Cylinder Installation).
Cylinder
Wear
• Since there is a difference in cylinder wear in different di- rections, take a side-to-side and a front-to-back measure-
ment at each of the two locations (total of four measure- ments) shown in the figure.
If any of the cylinder inside diameter measurements ex- ceeds the service limit, replace the cylinder.
10 mm (0.39 in.) [A]
60 mm (2.36 in.) [B]
Cylinder Inside Diameter
Standard: 82.994 83.006 mm (3.2675 3.2679 in.)
Service Limit: 83.10 mm (3.2716 in.)
Piston
Wear
• Measure the outside diameter [A] of each piston 18 mm (0.7087 in.) [B] up from the bottom of the piston at a right
angle to the direction of the piston pin.
If the measurement is under service limit, replace the pis- ton.
Piston Diameter
Standard: 82.969 82.984 mm (3.2665 3.2671 in.)
Service Limit: 82.82 mm (3.2606 in.)
Piston
Ring, Piston Ring Groove Wear
• Check for uneven groove wear by inspecting the ring seat- ing.
The rings should fit perfectly parallel to groove surfaces. If not, replace the piston and all the piston rings.
• With the piston rings in their grooves, make several mea-
surements with a thickness gauge [A] to determine piston
ring/groove clearance.
Piston Ring/Groove Clearance Top
Standard: 0.03 0.07 mm (0.0012 0.0028 in.)
Service Limit: 0.17 mm (0.0067 in.) Second
Standard: 0.02 0.06 mm (0.0008 0.0024 in.)
Service Limit: 0.16 mm (0.0063 in.)
Piston
Ring Groove Width
• Measure the piston ring groove width.
○Use a vernier caliper at several points around the piston.
Piston Ring Groove Width Top [A]
Standard: 0.92 0.94 mm (0.0362 0.0370 in.)
Service Limit: 1.02 mm (0.040 in.) Second [B]
Standard: 1.01 1.03 mm (0.0398 0.0406 in.)
Service Limit: 1.11 mm (0.044 in.)
If the width of any of the two grooves is wider than the service limit at any point, replace the piston.
Piston
Ring Thickness
• Measure the piston ring thickness.
○Use the micrometer to measure at several points around
the ring.
Piston Ring Thickness Top [A]
Standard: 0.87 0.89 mm (0.0342 0.0350 in.)
Service Limit: 0.80 mm (0.031 in.) Second [B]
Standard: 0.97 0.99 mm (0.0382 0.0390 in.)
Service Limit: 0.90 mm (0.035 in.)
If any of the measurements is less than the service limit on either of the rings, replace all the rings.
NOTE
○When using new rings in a used piston, check for un-
even groove wear. The rings should fit perfectly parallel
to the groove sides. If not, replace the piston.
Piston
Ring End Gap
• Place the piston ring [A] inside the cylinder, using the pis- ton to locate the ring squarely in place. Set it close to the
bottom of the cylinder, where cylinder wear is low.
• Measure the gap [B] between the ends of the ring with a thickness gauge.
Piston Ring End Gap Top
Standard: 0.25 0.40 mm (0.0098 0.0157 in.)
Service Limit: 0.7 mm (0.028 in.) Second
Standard: 0.40 0.55 mm (0.0157 0.0217 in.)
Service Limit: 0.8 mm (0.031 in.)
If the end gap of either ring is greater than the service limit, replace all the rings.