Page 10-0


Page 10-1

10. CYLINDER/PISTON

SERVICE INFORMATION 10-1
TROUBLESHOOTING 10-1
CYLINDER 10-2
PISTON 10-3
PISTON RING INSTALLATION 10-5
PISTON INSTALLATION 10-5
CYLINDER INSTALLATION 10-5    (page number corrected)

SERVICE INFORMATION

GENERAL


SPECIFICATIONS

Unit: mm (in)


ITEM STANDARD SERVICE LIMIT
Cylinder I.D. 79.000-79.015   (3.1102-3.1108) 79.05   (3.112)
Warpage across top 0.10   (0.004)
Taper 0.06   (0.002)
Out-of-round 0.06   (0.002)
Piston,
piston
rings
and piston
pin
Piston ring-to-ring groove clearance TOP 0.025-0.055   (0.001-0.002) 0.11   (0.004)
SECOND 0.015-0.045   (0.0006-0.0018) 0.10   (0.004)
Ring end gap TOP 0.20-0.35   (0.008-0.014) 0.65   (0.026)
SECOND 0.35-0.50   (0.014-0.020) 0.65   (0.026)
OIL 0.20-0.80   (0.008-0.031) 0.95   (0.037)
Piston O.D. 78.970-78.990   (3.1086-3.1098) 78.92   (3.107)
Piston pin bore 20.002-20.008   (0.7874-0.7877) 20.018   (0.7881)
Connecting rod small end I.D. 20.016-20.034   (0.7880-0.7887) 20.04   (0.789)
Piston pin O.D. 19.994-20.000   (0.7871-0.7874) 19.984   (0.7867)
Piston-to-piston pin clearance 0.002-0.014   (0.0001-0.0006) 0.034   (0.0013)
Cylinder-to-Piston clearance 0.010-0.035   (0.0004-0.0014) 0.13   (0.005)
Piston pin-to-connecting rod
small end clearance
0.016-0.040   (0.0006-0.0016) 0.060   (0.0024)

TROUBLESHOOTING

Low or uneven compression

Excessive smoke

Overheating

Piston noise


Page 10-2


CYLINDER

REMOVAL

Remove the following:

Disconnect the water hose from the coolant connector.



Remove the clip and slide the cylinder joint collar toward either the front or rear cylinder.

Remove the cylinder to be serviced.
Remove the cylinder gasket and dowel pins from the crankcase.



INSPECTION

Clean the top of each cylinder thoroughly.

Inspect the cylinder walls for scratches and wear.

Measure and record the cylinder I.D. at three levels in both an X and Y axis.  Take the maximum reading to determine the cylinder wear.

SERVICE LIMIT: 79.05 mm (3.112 in)

Calculate the piston-to-cylinder clearance.  Take the maximum reading to determine the clearance.

SERVICE LIMIT: 0.13 mm (0.005 in)

Calculate the cylinder for taper at three levels in an X and Y axis.  Take the maximum reading to determine the taper.

SERVICE LIMIT: 0.06 mm (0.002 in)



Calculate the cylinder for out-of-round at three levels in an X and Y axis.  Take the maximum reading to determine the out-of-round.

SERVICE LIMIT: 0.06 mm (0.002 in)

The cylinder must be rebored and an oversize piston fitted if the service limits are exceeded.

The following oversize pistons are available:
   0.25 mm (0.010 in) and 0.50 mm (0.020 in)

The cylinder must be rebored so that the clearance to an oversize piston is 0.010-0.035 mm (0.0004-0.0014 in).


Page 10-3



Inspect the cylinders for transverse warpage across the top.

NOTE



SERVICE LIMIT: 0.10 mm (0.004 in)



PISTON

REMOVAL

Place a shop towel into the crankcase and remove the piston pin clips.

NOTE





href="#10-3-piston-inspection" name="10-3-piston-inspection" >INSPECTION

Clean the piston domes, ring lands and skirts.

Measure the piston ring-to-groove clearance.

SERVICE LIMITS:
Top:0.11 mm (0.004 in)
Second:0.10 mm (0.004 in)

If clearance is excessive, replace the piston ring.



Remove the piston rings and mark them to indicate the correct cylinder and piston position for reassembly.

NOTE




Page 10-4



Measure the piston O.D.

NOTE



SERVICE LIMIT: 78.92 mm (3.107 in)

Calculate the piston-to-cylinder clearance by subtracting the piston O.D. from the cylinder I.D.  (page 10-2).

SERVICE LIMIT: 0.13 mm (0.005 in)


Measure the top and second piston ring end gaps: using a piston, push the ring into the cylinder squarely and make the measurement.

SERVICE LIMITS:
Top:0.65 mm (0.026 in)
Second:0.65 mm (0.026 in)
Oil:0.95 mm (0.037 in)


Measure each piston pin bore.

SERVICE LIMIT: 20.018 mm (0.7881 in)

Measure each piston pin O.D.

SERVICE LIMIT: 19.984 mm (0.7867 in)

Calculate the piston pin-to-piston clearance.

SERVICE LIMIT: 0.034 mm (0.0013 in)



Measure the I.D. of the connecting rod small end.

SERVICE LIMIT: 20.04 mm (0.789 in)

Calculate the piston pin-to-connecting rod clearance.

SERVICE LIMIT: 0.060 mm (0.0024 in)

Refer to section 11 for connecting rod replacement.


Page 10-5


PISTON RING INSTALLATION

NOTE



Carefully install the piston rings onto the piston with the markigs facing up.

NOTE



Stagger the ring end gaps 120° apart from each other as shown.

NOTE



After installing the rings, check that they rotate freely without sticking.



PISTON INSTALLATION

Place a shop towel into the crankcase.
Coat the rod small end with molybdenum disulfide grease.  Assemble the piston and connecting rod with the piston and Piston pin clips as shown.

NOTE





CYLINDER INSTALLATION

Clean the cylinder gasket surface.

Install the dowel pins and new gasket.


Page 10-6


Coat the cylinder, piston ringslgrooves and piston with clean engine oil.

Install the piston assembly into the cylinder from the top of the crankcase while compressing the piston rings with your fingers.
Be sure each assembly is returned to its original position as noted during removal.

NOTE





Install a new O-ring onto the cylinder joint and install the cylinder joint collar by sliding the collar toward either cylinder.

Install the clips securely.



Install a new O-ring into the connector and install and tighten the connector mounting bolts, if the connector was removed.

If only the water hose was removed, connect the hose with the clamp.



Clean the cylinder gasket surface.

NOTE



Install the cam chain guide.

NOTE



Install the dowel pins and a new gasket.
Install the cylinder heads and covers (Section 9).