TROUBLESHOOTING
Engine
Engine Turns Over But Fails to Start
• No fuel
• Dirt in fuel line or filter
• Fuel will not pass through fuel valve
• Fuel pump inoperative/restricted
• Tank vent plugged
• Carb starter circuit
• Engine flooded
• Low compression (high cylinder leakage)
• No spark (Spark plug fouled)
Engine Does Not Turn Over
• Dead battery
• Starter motor does not turn
• Engine seized, rusted, or mechanical failure
Engine Runs But Will Not Idle
• Restricted carburetor pilot system
• Carburetor misadjusted
• Choke not adjusted properly
• Low compression
• Crankcase breather restricted
Engine Idles But Will Not Rev Up
• Spark plug fouled/weak spark
• Broken throttle cable
• Obstruction in air intake
• Air box removed (reinstall all intake components)
• Incorrect or restricted carburetor jetting
• ETC switch limiting speed
• Reverse speed limiter limiting speed
• Carburetor vacuum slide sticking/diaphragm damaged
• Incorrect ignition timing
• Restricted exhaust system
Engine Has Low Power
• Spark plug fouled
• Cylinder, piston, ring, or valve wear or damage (check compression)
• PVT not operating properly
• Restricted exhaust muffler
• Carburetor vacuum slide sticking/diaphragm damaged
• Dirty carburetor
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
• Excessive piston-to-cylinder clearance
• Wet sumping
• Worn rings, piston, or cylinder
• Worn valves, guides or seals
• Restricted breather
• 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 sealing surface)
• Rocker arm sticking
Backfiring
• ETC or speed limiter system malfunction
• Fouled spark plug or incorrect plug or plug gap
• Carburetion faulty - lean condition
• 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
• Valve sticking
• Air leaks in intake
• Lean condition
Spark Plug Fouling
• Spark plug cap loose or faulty
• Choke cable adjustment or plunger/cable sticking
• Foreign material on choke plunger seat or plunger
• Incorrect spark plug heat range or gap
• Carburetor inlet needle and seat worn
• Jet needle and/or needle jet worn or improperly adjusted
• Excessive carburetor vibration (loose or missing needle jet locating pins)
• Loose jets in carburetor or calibration incorrect for altitude/temperature
• Incorrect float level setting
• PVT system calibrated incorrectly or components worn or mis-adjusted
• Fuel quality poor (old) or octane too high
• Low compression
• Restricted exhaust
• Weak ignition (loose coil ground, faulty coil, stator, or ETC switch)
• ETC switch mis-adjusted
• Restricted air filter (main or pre-cleaner)
• Improperly assembled air intake system
• Restricted engine breather system
• Oil contaminated with fuel
• Restricted oil tank vent
Cooling Troubleshooting
Overheating
• Low coolant level
• Air in cooling system
• Wrong type of coolant
• Faulty pressure cap or system leaks
• Restricted system (mud or debris in radiator fins or restriction to air flow, passages blocked in radiator, lines, pump, or water jacket)
• Lean mixture (restricted jets, vents, or fuel pump)
• Fuel pump output weak
• Restricted radiator (internally or cooling fins)
• Water pump failure
• Cooling system restriction
• Cooling fan inoperative or turning too slowly
• Ignition timing misadjusted
• Low oil level
• Spark plug incorrect heat range
• Faulty hot light circuit
• Thermostat stuck closed or not opening completely
• Radiator is missing its internal diverter plate not allowing coolant to flow through entire radiator
Temperature Too Low
• Thermostat stuck open
Leak at Water Pump Weep Hole
• Faulty water pump mechanical seal (coolant leak)
• Faulty pump shaft oil seal (oil leak)
TROUBLESHOOTING
Fuel Starvation / Lean Mixture
Symptoms: Hard start or no start, bog, backfire, popping through intake / exhaust, hesitation, detonation, low power, spark plug erosion, engine runs hot, surging, high idle, idle speed erratic.
• No fuel in tank
• Restricted tank vent, or routed improperly
• Fuel lines or fuel valve restricted
• Fuel filter plugged
• Carburetor vent line(s) restricted
• Plugged or restricted inlet needle and seat screen or inlet passage
• Clogged jets or passages
• Float stuck, holding inlet needle closed or inlet needle stuck
• Float level too low
• Fuel pump inoperative
• Air leak at impulse line
• Restricted impulse line (kinked, pinched)
• Intake air leak (throttle shaft, intake ducts, airbox or air cleaner cover)
• Ruptured vacuum slide diaphragm, Vacuum slide stuck closed or sticky
• Improper spring
• Jet needle position incorrect
• Incorrect pilot screw adjustment
Rich Mixture
Symptoms: Fouls spark plugs, black, sooty exhaust smoke, rough idle, poor fuel economy, engine runs rough/ misses, poor performance, bog, engine loads up, backfire.
• Air intake restricted (inspect intake duct)
• Air filter dirty/plugged
• Choke plunger sticking, incorrectly adjusted choke
• Choke cable binding or improperly routed
• Incorrect pilot air/fuel screw adjustment
• Faulty inlet needle and seat
• Faulty inlet needle seat O-Ring
• Float level too high
• Poor fuel quality (old fuel)
• Loose jets
• Worn jet needle/needle jet or other carburetor parts
• Dirty carburetor (air bleed passages or jets)
• Weak or damaged vacuum piston return spring
• Fouled spark plug
Idle Too High
• Idle adjusted improperly/idle mixture screw damaged
• Sticky vacuum slide
• Throttle cable sticking, improperly adjusted, routed incorrectly
• Choke cable sticking, improperly adjusted, routed incorrectly
• Plugged or restricted idle jet
Idle Too Low
• Choke cable bending or incorrectly adjusted
• Idle speed set incorrectly
• Idle mixture screw misadjusted or damaged
• Belt dragging
• Ignition timing incorrect
• Worn jet needle/needle jet
• Plugged or restricted idle jet
Erratic Idle
• Choke cable bending or incorrectly adjusted
• Throttle cable incorrectly adjusted
• Air leaks, dirty carburetor passages (pilot circuit)
• Pilot mixture screw damaged or adjusted incorrectly
• Tight valves
• Ignition timing incorrect
• Belt dragging
• Dirty air cleaner
• Engine worn
• Spark plug fouled
• Idle speed set incorrectly (speed limiter)
• Worn jet needle/needle jet
• Plugged or restricted idle jet
TROUBLESHOOTING
Troubleshooting Checklist
Check the following items when shifting difficulty is encountered.
• Idle speed adjustment
• PVT alignment
• Transmission oil type/quality
• Transmission torque stop adjustment (where applicable)
• Engine torque stop adjustment (where applicable)
• Drive belt deflection
• Loose fasteners on rod ends
• Loose fasteners on selector box
• Worn rod ends, clevis pins, or pivot arm bushings
• Linkage rod adjustment and rod end positioning
• Shift selector rail travel
• *Worn, broken or damaged internal transmission components
NOTE: To determine if shifting difficulty or problem is caused by an internal transmission problem, isolate the transmission by disconnecting linkage rod from transmission bellcrank. Manually select each gear range at the transmission bellcrank, and test ride vehicle. If it functions properly, the problem is outside the transmission. If transmission problem remains, disassemble transmission and inspect all gear dogs for wear (rounding), damage. Inspect all bearings, circlips, thrust washers and shafts for wear.
TROUBLESHOOTING
Brakes Squeal / Poor Brake Performance
• Air in system
• Water in system (brake fluid contaminated)
• Caliper/disc misaligned
• Caliper dirty or damaged
• Brake line damaged or lining ruptured
• Worn disc and/or friction pads
• Incorrectly adjusted stationary pad
• Worn or damaged master cylinder or components
• Damaged break pad noise insulator
Pedal Vibration
• Disc damaged
• Disc worn (runout or thickness variance exceeds service limit)
Caliper Overheats (Brakes Drag)
• Compensating port plugged
• Pad clearance set incorrectly
• Parking brake lever incorrectly adjusted
• Brake pedal binding or unable to return fully
• Parking brake left on
• Residue build up under caliper seals
• Operator riding brakes
Brakes Lock
• Alignment of caliper to disc
• Caliper pistons sticking
• Improper assembly of brake system components
Ignition System Troubleshooting
No Spark, Weak or Intermittent Spark
• Spark plug gap incorrect
• Fouled spark plug
• Faulty spark plug cap or poor connection to high tension lead
• Related wiring loose, disconnected, shorted, or corroded
• Faulty ignition switch
• Wire harness or connections wet, corroded.
• Poor ignition coil ground (e.g. coil mount loose or corroded)
• Faulty stator (measure resistance of all ignition related windings)
• Incorrect wiring (inspect color coding in connectors etc.)
• Faulty ignition coil winding (measure resistance of primary and secondary)
• Worn magneto (RH) end Crankshaft bearings
• Sheared flywheel key
• Flywheel loose or damaged
• Trigger coil air gap too wide (where applicable) - should be .016 - .030" (.4 - .75 mm)
• Excessive crankshaft runout on magneto (RH) end - should not exceed .0024”
• Faulty CDI module
Troubleshooting
Starter Motor Does Not Run
• Battery discharged - Low specific gravity
• Loose or faulty battery cables or corroded connections (see Voltage Drop Tests)
• Related wiring loose, disconnected, or corroded
• Poor ground connections at battery cable, starter motor or starter solenoid (see Voltage Drop Tests)
• Faulty key switch
• Faulty starter solenoid or starter motor
• Engine problem - seized or binding (can engine be rotated easily)
Starter Motor Turns Over Slowly
• Battery discharged - low specific gravity
• Excessive circuit resistance - poor connections (see Voltage Drop Test)
• Engine problem - seized or binding (can engine be rotated easily)
• Faulty or worn brushes in starter motor
Starter Motor Turns - Engine Does Not Rotate
• Faulty starter drive
• Faulty starter drive gears or starter motor gear
• Faulty flywheel gear or loose flywheel