The Complete Guide to Go Kart Transmission

The Go Kart consists of many components to transfer power from the engine to the wheels, consequently driving the kart. The kart consists of the chassis, engine, steering, and transmission, making the structure complete.

The transmission gives total control over the power generated by the engine. There are various transmission types, and we will discuss the details in the article.

What is a Transmission?

The transmission is one of the main components of the Go Kart. It delivers the power from the rotary movement of the engine’s crankshaft to the axle of the kart. The karts are usually rear-wheel drive; hence the transmission is connected to the rear axle.

The three most common types of transmission on the Go Kart are No Transmission (Direct Drive), Automatic Transmission (Clutch and Torque Converter), and Manual Transmission (Gear Box).

Each transmission has its benefits and can be used in peculiar karts according to their needs. They are used in different karts and purposes; most homemade karts are direct drive or automatic, and a manual transmission is used in professional racing karts.

Direct Drive Kart

The Direct Drive Kart doesn’t have a transmission built. Most smaller karts, electric karts, and homemade karts are direct drives to save space and keep the kart simple. Usually, the power is transferred directly from the engine to the axle through a roller chain or sprocket.

The kart doesn’t have a variable adjusted power transfer and must be engaged with the rear axle. Hence cannot stay at an idle position once the engine start and rotational movement begin.

Accelerator and brake pedals can adjust the go-kart speed; the gear ratio stays the same, and the driver cannot adjust the torque of the engine RPM through the transmission.

Electric go-karts are direct drives as they commute through electric speed controllers; however, gas-powered go-karts are mostly automatic transmissions or manual transmissions.

The Direct drive is the cheapest to build and works well with small electric karts. They cannot stay idle, and parts wear higher because of the constant rotational movement. It’s usually used in recreational parks for junior drivers.

Automatic Transmission

Automatic Transmission go kart

The Automatic transmission can engage and disengage the engine crank at certain Rpm’s, providing the best gear to utilize the maximum power from the engine. The kart can stay at an idle position when the transmission is disengaged. The two main types of Automatic transmission are the Clutch and Torque Converter Transmission.

Go Kart Clutch

The Clutch transmission is an automatic non-variable transmission used in go-karts. The engine is powered by a rear axle through a chain drive. The clutch is connected to the crankshaft and consequently connects the rear axle shaft from the other end, transmitting the rotational movement of the crankshaft to the rear axle, hence driving the kart’s wheels.

The transmission is non-variable; as a result, the gear ratio is constant, and the rotational movement of the crank and axle wheel will be constant and cannot vary.

Working on a Clutch Transmission

  • As the rpm of the crankshaft reaches 1400 to 1600, it engages the clutch and creates enough external force to expand the tension spring and causes the flyweight or shoe to move outwards.
  • This makes the frictional material physically contact the inner drum of the clutch; once complete contact is made, the clutch is fully engaged with the shaft.
  • The clutch spins around with the crankshaft and makes the rear wheel spin through a chain; this occurs at 1800 RPM.
  • Operating the engine at lower RPM is not recommended as it causes slippage between the clutch; hence, it’s used in go-karts that constantly accelerate at higher speeds.

Related: Our in-depth article on how go-kart clutch work

Types of Clutch Transmission

  • Centrifugal Clutch: They are common in go-karts as it’s cheap and straightforward to build the clutch on the kart working manually through springs, flyweight, and chain.
  • Belt Clutch: The clutch operates through belts instead of chains; the driving pulley and driven pulley are connected through belts. The wear of the belt is one of the draw-back of the clutch.
  • Hydraulic Clutch: The working of the clutch is performed through hydraulic fluid instead of mechanical parts.
  • Electric Clutch: The electrically controlled transmitters provide power from the crank to the rear wheel axle; these are expensive to build.

The Honda GX160 is an example of a clutch transmission engine used in Go Karts.

Go Kart Torque Converter

The Torque Converter has a variable transmission, meaning their gear ratio changes concerning the rpm. The Gear Ratio is the teeth ratio between the driver pulley and the driven pulley; at lower rpm, the gear ratio increases to adjust the rotational movement of the crankshaft, and the gear ratio decreases as the crank start spinning at a greater rate.

The torque converter is ideal for go-karts with heavy loads or inclined surfaces to produce the required power at lower rpm. These are primarily used in off-road karts and homemade karts.

Check our best off-road go-kart article.

The main component consists of the pulleys, which rotate between the crank and the axle; between the pulleys are belts that transfer the rotational force from the engine to the pulley. The converter engages fully at the rpm of 1500; before the rpm, the kart can stay idle. One of the advantages of the torque converter is that it engages at a lower rpm, and the kart can drive.

Working on Torque Converter Transmission

  • The crankshaft connects the driver pulley; once the crank maintains a particular rpm, the pulley clamps to the belt, causing the pulley to rotate.
  • Belts connect the driver pulley and driven pulley once the driver pulley spins; the driven pulley also rotates hence it changes the gear ratio.
  • The rear axle is connected to the driver pulley through a chain and sprocket, it provides rotary movement for the axle, and the kart wheels start moving.
  • Below 1500 rpm, the pulley is disengaged, the kart stays in an idle position, and the wear of the torque converter transmission is shallow.

Suzuki access 125 is a standard engine for continuously variable transmission used in karts.

Manual Transmission

The manual transmission on go-karts is maneuvered through gearboxes; the driver can choose the best gear ratio setting at different intervals while driving. Go Karts with manual transmission are typically known as shifter karts and are used in the United States and throughout Europe.

Commonly used in professional races, shifter karts have a six-speed manual gearbox attached for drivers to change the gear through the gear knob. You also check our go-kart racing classes article.

Go Kart Gear Box

The gearbox is built into the engine and is most commonly a six-speed gear transmission, it has multiple gear ratios, and the driver can choose the best gear for different speeds. The maintenance should be done at timely intervals as the mechanical parts in the gearbox need change of lubricants.

Working on Gear Box

  • Six-speed manual racing karts have a gearbox attached with a clutch; the clutch is used with the gear knob to switch between gears.
  • The gears are attached to the main shaft and can be switched manually by the gear knob; each gear has a different gear ratio, at lower rpm, the first gear is recommended, and the driver can switch out gears as the speed increases.
  • The gear is engaged with the rear axle of the kart, and when the gear is neutral, it can stay idle; while the gear is engaged, it rotates the axle making the kart move.

The Bajaj pulsar 135 engine has a gearbox built to drive the go-kart.

Which Transmission is Recommended?

The answer depends on the purpose of your go-kart; as we have explored above, the transmission is best suited for different purposes. We can categorize this:

  • Clutch Transmission: Racing Go Karts, lightweight, and high-speed karts.
  • Torque Converter Transmission: Off-road Go karts, for heavy loads and low rpm drive.
  • Gearbox Transmission: Shifter Karts, professional karts, with manual gear switching allowing more control.

Each transmission has moving mechanical parts; hence reliability depends on the maintenance done by the driver. The clutch transmission has a chain that wears with time, and torque converters have belts that have the same issue of wear with the frictional movement of surfaces. Gearboxes are complex with multiple moving objects along with the clutch cable, which can lock up due to excessive use.

Final Thoughts

The kart transmission is vital and should be well-maintained for smooth rides. The type of transmission chosen depends on the particular purpose the kart is driven for; each transmission has its pros and cons, and you need to be the judge when deciding the transmission to install.

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