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9850043 R01 - 2017-2021 RANGER 500 / 570 Service Manual
© Copyright Polaris Inc.
ENGINE HAS LOW POWER
• Spark plug fouled
• Cylinder, piston, ring, or valve
wear or damage (check
compression)
• Poor fuel quality
• PVT not operating properly
• Cam worn excessively
• Restricted exhaust muffler
• Low fuel pressure
PISTON FAILURE - SCORING
• Lack of lubrication
• Improper air filter maintenance
• Dirt entering engine through
cracks in air filter or ducts
• Engine oil dirty or contaminated
EXCESSIVE SMOKE (BLUE / BLACK) AND CARBON BUILDUP
• Excessive piston-to-cylinder
clearance
• Wet sumping
• Worn rings, piston, or cylinder
• Worn valve guides or seals
• Restricted breather
• Air filter dirty or contaminated
LOW COMPRESSION
• Cylinder head gasket leak
• No valve clearance (cam wear)
• Valve not seating properly (bent or
carbon accumulated on sealing
surface)
• Cylinder or piston worn
• Bent valve or stuck valve
• Piston rings worn, leaking, broken,
or sticking
• Valve spring broken or weak
BACKFIRING
• Ignition system faulty:
– Spark plug cap cracked /
broken
– Ignition coil faulty
– Ignition or kill switch circuit
faulty
– Poor connections in ignition
system
– Ignition timing incorrect
– Sheared flywheel key
• Intake system air leaks
• Fouled spark plug or incorrect plug
or plug gap
• Low fuel pressure
• Poor fuel quality
• Exhaust system air leaks
• Valve sticking
• Throttle Body (installed incorrect /
electrical concern / failed)
GENERAL INFORMATION
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