COMPONENT LOCATION

SERVICE INFORMATION

GENERAL

• This section covers maintenance of the cylinder and piston. These procedures can be done with the engine installed in the frame.

• Before disassembly, clean the engine thoroughly to prevent dirt from entering it.

• Be careful not to damage the mating surfaces when removing the cylinder. For example, do not use a screwdriver to pry the cylinder.

• Clean all disassembled parts with cleaning solvent before inspection, use compressed air to dry the parts.

• Under racing conditions, the piston and piston rings should be replaced after 15.0 hours of operation. Replace the pis­ton pin after 30.0 hours of operation.

SPECIFICATIONS

Unit: mm (in

ITEM

STANDARD

SERVICE LIMIT

Cylinder

I. D.

96.000 — 96.015 (3.7795 — 3.7801)

96.025 (3.7805)

Out of round

0.010 (0.0004)

Taper

0.010 (0.0004)

Warpage

0.05 (0.002)

Piston, piston ring

Piston mark direction

"IN" mark facing toward the intake side

Piston O. D.

95.970 — 95.980 (3.7783 — 3.7787)

95.94 (3.777)

Piston O. D. measurement point

5.0 mm (0.20 in) from the bottom of skirt

Piston pin bore I. D.

19.002 — 19.008 (0.7481 — 0.7483)

19.03 (0.749)

Piston pin O. D.

18.994 — 19.000 (0.7478 — 0.7480)

18.98 (0.747)

Piston-to-piston pin clearance

0.002 — 0.014 (0.0001 — 0.0006)

0.04 (0.002)

Top ring mark

"R" mark side facing up

Piston ring-to-ring groove clearance

Top

0.065 — 0.100 (0.0026 — 0.0039)

0.115 (0.0045)

Piston ring end gap

Top ring

0.25-0.31 (0.010-0.012)

0.45 (0.018)

Oil ring (side rail)

0.20-0.70(0.008-0.028)

0.90 (0.035)

Cylinder-to-piston clearance

0.020 — 0.045 (0.0008 — 0.0018)

0.085 (0.0033)

Connecting rod small end I. D.

’05 — ’07

19.016 — 19.034 (0.7487 — 0.7494)

19.04 (0.750)

After ’07

19.016 — 19.038 (0.7487 — 0.7495)

19.04 (0.750)

Connecting rod-to-piston pin clearance

’05 — ’07

0.016 — 0.040 (0.0006 — 0.0016)

0.06 (0.002)

After ’07

0.016 — 0.044 (0.0006 — 0.0017)

0.06 (0.002)

TORQUE VALUE

Cam chain tensioner lifter mounting bolt 12 N-m (1.2 kgf-m, 9 Ibf ft)

TROUBLESHOOTING

• Engine top-end problems usually affect engine performance. These problems can be diagnosed by a compression test or by tracing engine noise to the top-end with a sounding rod stethoscope.

• If the performance is poor at low speeds, check for white smoke in the crankcase breather hose. If the hose is smoky, check for a seized piston ring.

Compression too low, hard starting or poor performance at low speeds

• Leaking cylinder head gasket

• Worn, stuck or broken piston rings

• Worn or damaged cylinder and piston

• Loose spark plug

Compression too high, over-heating or knocking

• Excessive carbon build-up in cylinder head or on top of piston

Abnormal noise

• Worn cylinder and piston

• Worn piston pin or piston pin hole

• Worn connecting rod small end

• Worn connecting rod big end

Excessive smoke

• Worn cylinder, piston and piston rings

• Improper installation of piston rings

• Scored or scratched piston or cylinder wall

COMPONENT LOCATIONCYLINDER REMOVAL

Remove the cylinder head (page 9-24). Remove the cam chain guide.

CAM CHAIN GUIDE

CYLINDER

GASKET

BOLTS

Remove the bolts, cam chain tensioner lifter and gasket.

Remove the bolt and cylinder.

COMPONENT LOCATION

BOLT

CAM CHAIN TENSIONER LIFTER

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