Page 384 - 2019 SHOP MANUAL CRF1000/A/D

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CRANKSHAFT/PISTON/CYLINDER
SERVICE INFORMATION
CRANKSHAFT/PISTON/CYLINDER
GENERAL
• The crankcase must be separated to service the crankshaft and pistons and connecting rods.
• Mark and store the connecting rods, bearing caps, and bearing inserts to be sure of their correct locations for reassembly.
• The crankpin and main journal bearing inserts are select fit and are identified by color codes. Select replacement bearings from
the code tables. After selecting new bearings, recheck the oil clearance with plastigauge. Incorrect oil clearance can cause
major engine damage.
• Clean the oil passages in the upper crankcase with compressed air before installing the pistons.

TROUBLESHOOTING
Cylinder compression is too low, hard to starting, or poor performance at low speed
• Leaking cylinder head gasket
• Loose spark plug
• Worn, stuck or broken piston ring
• Worn or damaged cylinder and piston
Cylinder compression too high, overheating, or knocking
• Excessive carbon built-up on piston head or combustion chamber
Excessive smoke
• Worn cylinder, piston, or piston ring
• Improper installation of piston rings
• Scored or scratched piston or cylinder wall
Abnormal noise
• Worn piston pin or piston pin hole
• Worn connecting rod small end
• Bent connecting rod
• Worn cylinder, piston, or piston rings
• Worn main journal bearings
• Worn crankpin bearings
Engine vibration
• Excessive crankshaft runout

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