Go Kart Projects
There are many styles of motorized karts, which include the yard kart, off-road kart, wagon kart, toolbox kart (cooler kart), and barstool racer. Race karts, or track karts, are designed for competitive racing and can only be driven on a race track (more on race karts below).
Today's yard kart, sometimes called a fun kart, is a direct descendant of the original go-karts from the fifties and sixties. They typically have a low, flat frame, no roll cage, and no suspension.
Yard karts were not designed for competitive racing or off-road riding, but rather for use on private property, a vacant parking lot, or around the neighborhood.
Designed for non-pavement use, such as woods, trails, dirt, mud, and sand, off-road karts can be a single or double seater. A tall roll cage provides driver/passenger protection and high suspension allows for plenty of ground clearance.
Go Kart Engine Choices
Back in the day, yard karts were usually powered by a 5-horsepower or less flathead engine.
A Honda GX160 or GX200 are great choices for a kart build. Honda clones are also popular because they're cheap to buy and easy to get more power from. But if you're building a vintage go kart, an old flathead motor is the way to go.
Fixed Axle (One Wheel Drive)
Go karts can use a variety of rear axle types. The most common for yard karts is the fixed, or "dead" axle. This is where a single wheel has a sprocket mounted to it and is driven by a chain from the engine. In this type of setup, the rear axle does not turn, and the rear wheels spin freely when off the ground.
Live Axle (Two Wheel Drive)
Off-road karts work best when both rear axles are getting power from the motor. This is known as a live axle setup. With both wheels turning at the same time, you have twice the traction on sand and loose dirt.
Live axles are best for traction, but not best for steering. On pavement, turning is difficult because both rear wheels are turning at the same speed. The outside wheel must be able to spin faster than the inside wheel, but because it can't "keep up", it will slip on the pavement.
Getting Power To The Ground
A centrifugal-type clutch is found on most yard karts and old-school karts. This is the cheapest and simplest way to get power to the rear wheel.
The downside of a centrifugal clutch is that they do not like "stop and go" (on and off) acceleration. If you drive your kart this way, the clutch will have a short life, so it's better to run pedal down or not at all.
Centrifugal clutches are designed for motors no larger than 200cc (12 cubic-inches).
Before you buy a go kart clutch, measure the width of your output shaft. Most 5-hp motors will have a 3/4" (.750) shaft, but older, small-hp engines may have a 5/8" (.625) shaft.
For a yard kart with 6" wheels, a 10-tooth clutch is a popular choice. For a little more power, but less top end, add more teeth. Example: Installing a 12-tooth clutch will give you quicker acceleration but less top speed.
Clutch vs Converter
An alternative to a centrifugal clutch is to install a small engine torque converter. This will give your kart better acceleration, and allow you to run the pedal on and off without the risk of burning up the clutch. For inclines and off-road hill climbing, a torque converter will provide the best power transfer from engine to rear wheels.
What Is A Jack Shaft?
For karting use, a jack shaft is primarily used to get a more favorable gear reduction or to relocate the chain drive because of clearance/fitment issues. This is done by having a secondary chain (or belt) from a small pulley to a larger pulley.
With a centrifugal clutch, the engine-mounted clutch connects to the jack shaft through a primary chain. The second pulley on the jack shaft is then connected to the rear axle with a secondary chain.
Sometimes a jack shaft is used to accommodate a torque converter. The jack shaft mounting plate can also be used for mounting a brake assembly.
Karts made specifically for competition are called race karts or track karts. They are designed to be driven on smooth, paved race tracks and sit extremely low to the ground. Powering these karts are heavily modified, 20+ horsepower engines.
A race kart engine putting out more than 20 horsepower will burn up torque converter belts. Because of this, most are fitted with a high-performance centrifugal clutch.
Read: Small Engine Performance
With the governor removed and pushed to the limit, small engines can and do blow up. If you're planning on building a performance motor, consider adding a steel firewall between you and the motor. This can be as simple as mounting a 16-gauge (or thicker) piece of sheet metal to the back of the seat.
Wear a Helmet
Motorized karts can be dangerous, so take proper safety precautions. When riding through your neighborhood, be respectful. Wear a helmet and obey traffic signs.
You Can't Beat Fun!