ENGINE
4-92
TROUBLESHOOTING
TROUBLESHOOTING
Engine Turns Over But Fails to Start
◎ No fuel
◎ Fuel injector carbon built.
◎ Fuel pressure less than 250kpa.
◎ Fuel pump inoperative/restricted
◎ Tank vent or fuel hose plugged
◎ Engine flooded
◎ Low compression (high cylinder leakage)
◎ No spark (Spark plug fouled)
◎ Spark plug coil lost power.
◎ Without valve clearance.
Engine Does Not Turn Over
◎ Dead battery
◎ Starter motor does not turn
◎ Engine seized, rusted, or mechanical failure
◎ One way clutch components damaged or sliding.
Engine Runs But Will Not Idle
◎ Restricted throttle pilot system.
◎ Air mixture screw misadjusted.
◎ Idle speed control valve failure.
◎ Low compression.
◎ Crankcase breather restricted.
◎ Air filter restriction.
◎ Oxygen sensor connects corrosion or short circuit.
Engine Idles But Will Not Accelerate
◎ Spark plug fouled/weak spark.
◎ Broken throttle cable.
◎ Obstruction in air intake.
◎ Air box removed (reinstall all intake components)
◎ Incorrect or restricted fuel injector.
◎ Reverse speed limiter limiting speed.
◎ Map fault.
◎ Incorrect ignition timing
◎ Restricted exhaust system
◎ Cam Lobe worn
Engine Has Low Power
◎ Spark plug fouled
◎ Restricted exhaust muffler
◎ Dirty carburetor
◎ Cam lobe worn
◎ Too much engine oil in crankcase.
◎ CVT not operating properly
◎ Cylinder, piston, ring, or valve wear or damage (check
compression)
Piston Failure - Scoring
◎ Lack of lubrication
◎ Dirt entering engine through cracks in air filter or ducts
◎ Engine oil dirty or contaminated
Excessive Smoke and Carbon Buildup
◎ Worn rings, piston, or cylinder
◎ Excessive piston-to-cylinder clearance
◎ Worn valves, guides or seals
◎ Restricted crankcase vent
◎ Air filter dirty or contaminated
Low Compression
◎ Decompressor stuck
◎ Cylinder head gasket leak
◎ No valve clearance or incorrectly adjusted
◎ Cylinder or piston worn
◎ Piston rings worn, leaking, broken, or sticking
◎ Bent valve or stuck valve
◎ Valve spring broken or weak
◎ Valve not seating properly (bent or carbon accumulated on
valve area)
◎ Rocker arm sticking
Backfiring
◎ Speed limiter system malfunction
◎ Fouled spark plug or incorrect plug or plug gap
◎ Map faulty - lean condition
◎ Intake / Exhaust system air leaks
◎ Ignition system faulty:
◎ Spark plug cap cracked/broken
◎ Ignition coil faulty
◎ Ignition or kill switch circuit faulty
◎ Ignition timing incorrect
◎ Sheared flywheel key
◎ Poor connections in ignition system
◎ System wiring wet
◎ Cam lobe worn or Valve sticking
◎ Lean condition
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General