Go Karts Trouble Shooting Guide
Trouble Shooting Guide For American Go Karts & Mini Bikes
This reference is designed to help service technicians find and eliminate problems associated with fun karts and mini bikes. It is not meant to be used as a service manual. To successfully use this guide: first, identify the major problem with the unit in question. Second, locate the most appropriate section below. Third, find the major problem in the section and check all possible causes listed. Possible causes are listed in order of probability; the most likely causes are listed first.
WARNING: Assembly, maintenance, and/or repair of the kart or mini bike should only be performed by persons of sufficient mechanical skill, experience, and judgement (such as outdoor power equipment or small engine dealers) so that no unsafe conditions or modifications are made.
GASOLINE ENGINES
Will Not Start:
Check gas and oil
Kill switch set to “off”
Choke improperly set
Engine flooded
Spark plug wire not connected
Clogged or wet air filter: The air filter functions as the lungs of the engine, if it is wet or clogged with dirt the engine is unable to “breathe” and 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 also prevent the engine from ingesting dirt and sand that damage internal working parts.
Throttle cable is grounding to engine stop terminal
Faulty start switch or battery (electric start units)
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 engine’s carburetor. If your engine has been sitting up with stale gasoline in the fuel tank your carburetor may require a soaking in carburetor cleaner to remove these deposits. Remove all 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 your fuel tank is clean and free of stale gas as well.
Will Not Stay Running:
Check gas and oil: If your 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 your engine’s gas tank and carb. do contain water it must be removed completely.
Loose spark plug wire or bad plug
Clogged or wet air filter
Faulty stop switch
Oil guard sensor is tripping (9hp Vanguard equipped units only)
Throttle cable is grounding to engine stop terminal
Carburetor not functioning properly
Seems Low On Power:
Throttle cable not properly adjusted
Binding or dragging brake, bearings or axle
Unlubricated, loose or worn chain
Incorrect tire pressure
Engine rpm’s not set properly
Throttle Will Not Return To Idle:
Throttle cable not properly adjusted
Throttle linkage not lubricated
Throttle linkage fastener too tight
Broken, weak, or stretched throttle pedal return spring
Broken, weak, or stretched engine throttle return spring
Engine throttle linkage binding
STOP AND START SWITCHES
Start Switch Does Not Work
Electric Start Units:
Check battery voltage and connections
Check start switch connectors
Faulty start switch
Faulty solenoid
Stop Switch Does Not Work:
Loose ground wire
Bad connection or broken wire
Loose terminal on engine
Faulty toggle switch
Faulty engine ground terminal
ELECTRICAL SYSTEM
Headlights Do Not Work:
Headlight burnt out
Bad connection or broken wire
Low Battery Voltage
Poor ground
DRIVE SYSTEMS
Centrifugal Clutch Equipped
Kart Moves While Engine Is Idling
Worn, overheated, or abused clutch - NOT OILED
Drive chain too tight
Engine idle is set too high
DRIVE SYSTEMS
Torque Converter Equipped
Kart Moves While Engine Is Idling
Drive belt installed wrong (30 Series only, flat side of belt should be towards the engine)
Wrong drive belt installed (a belt that is too short will cause the machine to “creep” at idle)
Malfunctioning driver pulley (on crankshaft)
Malfunctioning driven pulley (on jackshaft)
Incorrect driver pulley spacing
Engine idle set too high
Pulleys not aligned (will also destroy belts)
Rapid Belt Wear:
Drive belt installed wrong (30 Series only, flat side of belt should be towards the engine)
Wrong drive belt installed
Overloading drive system (climbing hills too steep, pulling heavy loads…)
Riding the brake
Malfunctioning driver pulley
Malfunctioning driven pulley
Binding or dragging brake, bearings or axle
Pulleys not aligned
NOTE: See The Comet Torque Converter Chart at the bottom of this page for more belt drive system trouble shooting Information.
Poor, Sluggish Or Jerky Acceleration:
Malfunctioning drive system
Throttle cable not properly adjusted
Unlubricated, loose, or worn drive chain
Binding or dragging brake, bearings or axle
Engine not functioning properly
Erratic Engagement:
Erratic engagement is most often caused by the driver clutch that is mounted 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 (pulley face) 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 such as Comet GP-370. The extreme heat and pressure inside the driver clutch chars most 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. Experience has taught us that the Comet GP-370 lubricant (or equivalent ) works best.
Low Speed:
Throttle cable not properly adjusted
Binding or dragging brake, bearings or axle
Malfunctioning drive system
Improper tire pressure
Engine not functioning properly
Drive Chain
Chain Falls Off Sprockets:
Chain tension too loose
Unlubricated, stretched or worn drive chain
Worn, overheated, or abused clutch
Sprockets not aligned
Bent, worn, or loose sprockets and or sprocket hubs
Loose drive wheel
Bent or loose axle
Bent frame
BRAKE SYSTEMS
Band Brake Equipped - Lining Wears Quickly:
Driver riding the brake
Brake rod or cable not properly adjusted
Kart Will Not Stop - Brake Does Not Work:
Brake rod or cable not properly adjusted
Brake band lining/pads worn
No key in brake drum/disk
No key in the wheel hub
Brake Binds Or Will Not Release:
Brake rod not properly adjusted
Brake linkage not lubricated
Brake linkage fastener too tight
Broken, weak, or stretched brake pedal return spring
STEERING
Steering Effort Too High:
Steering linkages not lubricated
Spindle pivot bolt too tight
Improper tire pressure
“Toe-In” not properly adjusted
Binding tie rod end
Bent spindle or tie rod
Bent front axle
Bent steering column