CYLINDER COMPRESSION TEST
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COMPRESSION GAUGE |
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To avoid discharging the battery, do not operate the starter motor for more than 7 seconds. |
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COMPRESSION: |
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Low compression can be caused by: - Improper valve adjustment - Valve leakage - Blown cylinder head gasket - Worn piston ring or cylinder - Faulty decompressor system High compression can be caused by: - Carbon deposits in combustion chamber or on piston head - Faulty decompressor system |
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Warm up the engine. Stop the engine and remove the spark plug (page 412). Connect a compression gauge. Open the throttle fully. Crank the engine with the electric starter or kickstarter until the gauge needle stops moving. The maximum reading is usually reached within 4-7 seconds when using electric starter. |
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402 kPa (4.1 kg/cm2, 58 psi) at 360 rpm |
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Remove the fuel tank (page 3-8).
Disconnect the spark plug cap and crankcase breather hose.
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CYLINDER HEAD COVER |
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PACKING |
Remove the bolts, cylinder head cover and packing.
Remove the plug hole seal.
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PLUG HOLE SEAL |
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CRANKSHAFT HOLE CAP/O-RING |
Remove the cylinder head cover (page 9-7). Remove the crankshaft hole cap and O-ring.
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Д" MARK |
Turn the crankshaft clockwise to align the punch mark on the primary drive gear with the "Д" mark on the right crankcase cover.
Make sure the piston is at TDC (Top Dead Center) on the compression stroke.
This position can be obtained by confirming that there is slack in the rocker arms. If there is no slack, rotate the crankshaft clockwise one full turn and align the punch mark on the primary drive gear with "Д" mark on the right crankcase cover again.
Check that the index line on the cam sprocket aligns with the "Д" mark on the camshaft holder.
PUNCH MARK
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BOLT/SEALING WASHER |
Remove the cam chain tensioner lifter bolt and sealing washer.
Insert the stopper tool into the cam chain tensioner lifter.
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Turn the stopper tool clockwise fully and lock the cam chain tensioner lifter by pushing the handle.
TOOL:
Tensioner stopper 070MG-0010100 or
07AMG-001A100 (U. S.A. only)
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BOLTS |
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DECOMPRESSOR CAM ASSEMBLY |
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x - / SPECIAL TOOL |
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BOLT |
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CAM SPROCKET |
A tool can easily be made from a thin (1 mm thick) piece of steel as shown.
Insert the special tool into the sprocket, over the gasket surface and loosen the one cam sprocket bolt.
• When the decompressor cam assembly will be disassembled, loosen the mounting bolt, but do not remove it yet.
TOOL:
Cam sprocket holder 07AMB-MEBA100 (U. S.A. only)
Be careful not to Remove the special tool, turn the crankshaft clock - drop the bolts into wise one turn and reinsert the special tool into the the crankcase, sprocket. Remove the other cam sprocket bolt.
Then remove the another cam sprocket bolt using the same procedure as removal of the other cam sprocket bolt.
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BOLTS |
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CAMSHAFT HOLDER ASSEMBLY |
Remove the cam sprocket from the camshaft, and suspend the cam chain with a piece of wire to prevent it from falling into the crankcase.
Make sure the piston is at TDC (Top Dead Center) on the compression stroke.
Loosen the camshaft holder bolts in a crisscross pattern in two or three steps.
Remove the camshaft holder assembly.
• Valve lifters are installed into the camshaft holder assembly.
• The shims may stick to the inside of the valve lifters. Do not allow the shims to fall into the crankcase.
Be sure lo mark the Remove the valve lifters from the camshaft holder
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VALVE LIFTERS
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valve lifters so they assembly. can be installed in their original positions.
Remove the circlip and nut.
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CIRCLIP |
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SPRING DECOMPRESSOR ARM |
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DECOMPRESSOR LIFTER MUI |
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STOPPER RING |
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Remove the decompressor lifter, spring and decompressor arm.
Remove the stopper ring.
Thread a 6 mm bolt into the rocker arm shaft, and pull the rocker arm shaft from the camshaft holder. Remove the rocker arm.
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ROCKER ARM |
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ROCKER ARM SHAFT |
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Remove the bolt, stopper plate and decompressor cam assembly.
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DECOMPRESSOR CAM ASSEMBLY BOLT |
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STOPPER PLATE |
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SNAP RING |
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INTAKE LOBES |
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Remove the snap ring and camshaft from the camshaft holder.
Make sure the intake lobes are facing up when removing the camshaft from the holder to prevent damaging the intake lifter bores.
