PISTON REMOVAL
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Place a clean shop towel over the crankcase to prevent the clip from falling into the crankcase. |
Remove the piston pin clips with pliers.
Press the piston pin out of the piston and remove the piston.
• Under racing conditions, the piston and piston rings should be replaced according to the competition maintenance schedule (page 4-6).
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Do not damage the piston ring by spreading the ends too far. |
Spread the piston rings and remove them by lifting up at a point just opposite the gap.
Inspect the cylinder bore for wear or damage. Measure the cylinder I. D. in the X and Y axes at three levels.
Take the maximum reading to determine the cylinder wear.
SERVICE LIMIT: 96.025 mm (3.7805 in)
Calculate the cylinder-to-piston clearance.
Take a maximum reading to determine the clearance. ^
For piston O. D. (page 10-7).
SERVICE LIMIT: 0.085 mm (0.0033 in)
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TOP MIDDLE BOTTOM |
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Calculate the taper and out-of-round at three levels in the X and Y axes. Take the maximum reading to determine the cylinder condition.
SERVICE LIMITS:
Taper: 0.010 mm (0.0004 in)
Out-of-round: 0.010 mm (0.0004 in)
Inspect the top of the cylinder for warpage. SERVICE LIMIT: 0.05 mm (0.002 in)
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Never use a wire brush. It will scratch the grooves. |
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PISTON RING |
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Remove the carbon deposits from the piston head or piston ring grooves.
Inspect the piston for damage and the ring grooves for wear.
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Temporarily install the top piston ring to its proper position with the mark facing up.
Measure the piston ring-to-ring groove clearance with the ring pushed into the groove.
SERVICE LIMIT: 0.115 mm (0.0045 in)
Inspect the piston ring grooves for wear or damage.
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Measure the diameter of the piston at 5.0 mm (0.20 in) from the bottom and 90 degrees to the piston pin hole.
SERVICE LIMIT: 95.94 mm (3.777 in)
If the O. D. is under the service limit or nearly 15.0 hours of running time have elapsed (competition use only), replace the piston with a new one.
Calculate the cylinder-to-piston clearance.
SERVICE LIMIT: 0.085 mm (0.0033 in)
Measure the piston pin bore I. D.
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PISTON RING |
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SERVICE LIMIT: 19.03 mm (0.749 in)
Check the piston pin for wear and excessive discoloration.
Measure the piston pin O. D.
SERVICE LIMIT: 18.98 mm (0.747 in)
If the O. D. is under the service limit, discolored, or nearly 30.0 hours of running time have elapsed (competition use only), replace the piston pin.
Calculate the piston-to-piston pin clearance.
SERVICE LIMIT: 0.04 mm (0.002 in)
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Push the ring into the cylinder wrth the top oi the piston to be sure the ring is squarely in the cylinder. |
Insert each piston ring into the cylinder and measure the ring end gap.
SERVICE LIMITS:
Top: 0.45 mm (0.018 in)
Oil (side rail): 0.90 mm (0.035 in)
Measure the connecting rod small end I. D.
SERVICE LIMIT: 19.04 mm (0.750 in)
If the I. D. is over the service limit, replace the crankshaft (page 13-14).
Calculate the connecting rod-to-piston pin clearance.
SERVICE LIMIT: 0.06 mm (0.002 in)
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Check the cam chain tensioner lifter operation:
- The tensioner shaft should not go into the body when it is pushed.
- When it is turned clockwise with a screwdriver, the tensioner shaft should be pulled into the body. The shaft should spring out of the body as soon as the screwdriver is released.
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PISTON RING INSTALLATION |
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Clean the piston grooves thoroughly. Apply engine oil to the piston rings and install them. • Do not damage the piston ring by spreading the ends too far. • Be careful not to damage the piston during piston ring installation. • Do not align the oil ring (side rails) gaps. • Space the piston ring end as shown. After installation, the rings should rotate freely in the ring grooves. |
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Install the top ring on the piston with the marked side facing up. |
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MARK |
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TOP RING |
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OIL RING |
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