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Go Kart Trouble Shooting

Mini Bike Trouble Shooting

This trouble shooting reference is designed to help service technicians find and eliminate problems with fun karts and mini bikes. It's not meant to be a service manual. Locate the most appropriate section below. Possible causes are listed in the order of probability; the most likely causes are listed first. Assembly, maintenance and repairs should only be performed by persons of sufficient mechanical skill, experience and judgement, so that no unsafe conditions or modifications are made.

Gasoline Engines

Engine Will Not Start

1. Check gas and oil

2. Kill switch set to "off"

3. Choke improperly set

4. Engine flooded

5. Spark plug wire not connected

6. Clogged or wet air filter: The air filter functions as the lungs of the engine, if it's wet or clogged with dirt the engine is unable to "breathe" and it may be difficult or impossible to start. Check your filter on a regular basis, more often if you ride in dusty conditions. Clean air filters prevent the engine from ingesting dirt and sand that damage internal working parts.

7. Throttle cable is grounding to engine stop terminal

8. Faulty start switch or battery: electric start units

9. Stale Fuel: Gasoline in a vented fuel tank can go stale within 60 days. Stale gas smells like varnish and leaves gummy deposits that clog the tiny jets of the carburetor. If the engine has been sitting up with stale gasoline in the fuel tank, the carburetor may require a soaking in carburetor cleaner to remove these deposits. Remove all the rubber pieces including the throttle shaft seal (o-ring) before soaking. After the carburetor is free of all bad gas deposits it should be reinstalled with new gaskets in place. Make sure the fuel tank is clean and free of stale gas as well.

Engine Won't Stay Running

1. Check gas and oil: If the engine has water in the gasoline, it will start, run for a few seconds, then as soon as the water hits the carburetor the engine will die. You can look in the bottom of the gas tank and see water "beading" around if it's present. If the gas tank and carburetor do contain water it has be removed completely.

2. Loose spark plug wire or bad plug

3. Clogged or wet air filter

4. Faulty stpo/kill switch

5. Oil guard sensor tripping (9hp Vanguard only)

6. Throttle cable grounding to engine stop terminal

7. Carburetor not functioning properly

Seems Low on Power -
Throttle Won't Return To Idle

1. Throttle cable not properly adjusted

2. Throttle linkage not lubricated

3. Throttle linkage fastener too tight

4. Broken, weak, or stretched throttle pedal return spring

5. Broken, weak, or stretched engine throttle return spring

6. Engine throttle linkage binding


Key Switch Won't Work
- Electric Start Units

1. Check battery voltage and connections

2. Check start switch connectors

3. Faulty start switch

4. Faulty solenoid

Kill Switch Won't Work

1. Loose ground wire

2. Bad connection or broken wire

3. Loose terminal on engine

4. Faulty toggle switch

5. Faulty engine ground terminal


Headlights Won't Work

1. Headlight burnt out

2. Bad connection or broken wire

3. Low Battery Voltage

4. Poor ground

Centrifugal Clutches

Kart Moves While Idling

1. Worn, overheated, abused Clutch, NOT OILED

2. Drive chain too tight

3. Engine idle is set too high

-- Visit the Service Tips Page to read about oiling Centrifugal Clutches that use just a Chain only.

-- Go Karts with rear tires taller than 15" require a Torque Converter.

Torque Converters

Kart Moves While Idling

1. Belt installed backwards (30 Series Only - Flat side goes towards engine)

2. Wrong belt installed, a belt that's too short will cause the machine to creep at idle

3. Malfunctioning driver clutch on crankshaft

4. Malfunctioning driven pulley on Jackshaft

5. Incorrect driver pulley spacing

6. Engine idle set too high

7. Pulleys not aligned, will narrow/destroy belts

Rapid Belt Wear

1. Drive belt installed wrong (30 Series Only, Flat side goes towards engine)

2. Wrong Belt installed

3. Overloading drive system; climbing hills too steep, pulling heavy loads

4. Riding the brake

5. Malfunctioning driver pulley

6. Malfunctioning driven pulley

7. Binding or dragging brake, bearings or axle

8. Pulleys not aligned

See the chart at the bottom of this page for more belt drive system trouble shooting.

Poor, Sluggish Or Jerky Acceleration

1. Malfunctioning drive system

2. Throttle cable not properly adjusted

3. Unlubricated, loose, or worn drive chain

4. Binding or dragging brake, bearings or axle

5. Engine not functioning properly

Erratic Engagement

1. Erratic engagement is most often caused by the driver clutch on the engine crankshaft. The flyweights in the clutch are sticking or the movable sheave is binding on the hub. Knowing how they work may help you determine why yours doesn't. As engine rpm increases, the flyweights push against the outer drum and force the movable sheave toward the engine causing the belt to travel at a greater circumference around the driver clutch. This action in turn causes the belt to force open the driven pulley, allowing the belt to travel at a lesser circumference around the driven pulley.

As engine rpm decreases, the spring in the driven pulley closes the pulley forcing the belt to a greater circumference. This action overcomes the force of the flyweights against the movable sheave and causes the driver clutch pulley to open, allowing the belt to travel a lesser circumference around the driver clutch. When the engine is at idle, the driver clutch pulley should not engage the sides of the belt. The belt should be loose in the pulley and resting on the bronze bushing around the hub. The bronze bushing serves to protect the belt from rubbing against the spinning hub at idle and also to support a portion of the movable sheave as the sheave moves toward the engine during engagement. The movable sheave must be able to slide freely on the splined hub without binding. Disassemble the driver clutch and clean away any dirt or lubricant residue using an automotive parts cleaning solvent. Do not use a petroleum based lubricant inside the driver clutch or between the hub and movable sheave. Use a dry, molybdenum based lubricant. The extreme heat and pressure inside the driver clutch chars petroleum based lubricants. Petroleum based lube also collects dirt which causes increased wear. Graphite lube is better than petroleum lube, but it also eventually leaves a residue that builds up on the parts, causing them to bind and require more frequent cleaning.

Low Speed

1. Throttle Cable not properly adjusted

2. Binding or dragging brake, bearings or axle

3. Malfunctioning drive system

4. Improper tire pressure

5. Engine not functioning properly


Chain Falls Off Sprockets

1. Chain tension too loose

2. Unlubricated, stretched or worn drive chain

3. Worn, overheated, or abused Clutch

Sprockets not aligned

5. Bent, worn, or loose sprockets & sprocket hubs

6. Loose drive wheel

7. Bent or loose axle

8. Bent frame


Band Brake - Lining Wears Quickly

1. Brake rod or cable not properly adjusted

2. The driver is "riding" the brake pedal too much.

* Remind the driver to push only one pedal at a time.

Kart Will Not Stop - Brake Doesn't Work

1. Brake rod or cable not properly adjusted

2. Brake band lining/pads worn

3. No key in brake drum/disk

4. No key in the wheel hub

Brake Binds Or Won't Release

1. Brake rod not properly adjusted

2. Brake linkage not lubricated

3. Brake linkage fastener too tight

4. Broken, weak or stretched brake pedal return spring


Steering Effort Too High

1. Linkages not lubricated

2. Spindle pivot bolt too tight

3. Improper Tire pressure

4. "Toe-In" not properly adjusted

5. Binding tie rod end

6. Bent Spindles or Tie Rods

7. Bent front axle

8. Bent steering column


Comet Torque Converter Belts




Belt is worn thin
in just one portion

Excessive slipping
of Clutch caused by:
Locked track or axle
Idle speed is too high

Rotate by hand to free up
Repair or replace clutch
Reduce the engine R.P.M.

Driver Clutch turns
while engine idles

Idle set too high
Wrong belt length, too short

Reduce engine R.P.M.
Check application specs.

Belt is worn "Cup"
Shaped, Concave on sides

Too much run out on clutch

Repair or replace clutch
Increase center distance

Belt Disintegration

Excessive Belt Speed

Reduce R.P.M. at high speed

Belt "Roll Over" at high speed

Pulley system out of line
Drive belt speed too high

Align system
Reduce the R.P.M.
Repair or replace clutch

Cord breakage on belt edge

Misalignment of system
Belt not properly installed

Align system

Cracking between cogs on belt

Belt is wearing out

Replace the belt

Broken or torn cogs
Compression section torn

Belt not installed right
Belt rubbing something

Check for interference

Belt worn uneven on one side

System out of line
Engine mount is loose

Align system
Tighten engine mount

Belt looks glazed/baked

Extra slippage caused by:
Not enough pressure on belt
Horsepower is too high
Possible oil on pulleys

Check driver springs & weights
Clean belt, pulley faces,
make sure they are dry

Top width worn too much

Excessive slipping
Pulleys are scratched/rough
Angle of the belt is wrong

Check for proper engagement
Replace or repair pulley
Check data for application

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