🏍️ Mini Bike Gear Ratio Calculator
Calculate gear ratio, top speed, wheel RPM, and torque multiplication for any mini bike or go-kart setup
Predator 212
Honda GX200
Ratio (stall)
Mini Bikes
Gear Ratio
Tire Diameter
Speed (mph)
Efficiency
| Drive Teeth | Driven Teeth | Ratio | Wheel RPM @ 3600 | Top Speed @ 12" Tire (mph) | Best For |
|---|---|---|---|---|---|
| 10 | 80 | 8.00:1 | 450 | 8.0 | Heavy load / hill climbing |
| 10 | 72 | 7.20:1 | 500 | 8.9 | Heavy trail / torque |
| 11 | 68 | 6.18:1 | 583 | 10.4 | Stock pocket bike |
| 12 | 72 | 6.00:1 | 600 | 10.7 | Balanced trail |
| 12 | 60 | 5.00:1 | 720 | 12.9 | Flat trail / mixed |
| 13 | 60 | 4.62:1 | 779 | 13.9 | Faster trail |
| 14 | 60 | 4.29:1 | 840 | 15.0 | Flat / semi-race |
| 14 | 54 | 3.86:1 | 933 | 16.6 | Race / flat track |
| 16 | 54 | 3.38:1 | 1067 | 19.0 | Speed build |
| 18 | 54 | 3.00:1 | 1200 | 21.4 | Max speed (ungoverned) |
| Chain Type | Pitch | Roller Width | Max RPM | Max Load (lbs) | Common Mini Bike Use |
|---|---|---|---|---|---|
| #35 | 3/8" (9.525mm) | 3/16" | 5000+ | ~880 | Pocket bikes, mini bikes ≤5HP |
| #40 | 1/2" (12.7mm) | 5/16" | 4000 | ~1500 | Go-karts, mini bikes 5–8HP |
| #41 | 1/2" (12.7mm) | 1/4" | 4200 | ~1200 | Light go-karts, mini bikes |
| #420 | 1/2" (12.7mm) | 1/4" | 5000 | ~1100 | Pocket bikes, ATV-style minis |
| #428 | 1/2" (12.7mm) | 5/16" | 4500 | ~1700 | Small motocross, trail mini |
| #50 | 5/8" (15.875mm) | 3/8" | 3000 | ~3000 | Heavy-duty 8HP+ builds |
| Engine | Displacement | Peak HP | Governed RPM | Peak Torque RPM | Rec. Gear Ratio |
|---|---|---|---|---|---|
| Predator 79cc | 79cc | 3.0 HP | 3600 | 2500 | 5.5:1 – 7:1 |
| Predator 212cc | 212cc | 6.5 HP | 3600 | 2500 | 5:1 – 6.5:1 |
| Honda GX160 | 163cc | 5.5 HP | 3600 | 2500 | 5:1 – 6.5:1 |
| Honda GX200 | 196cc | 6.5 HP | 3600 | 2500 | 4.5:1 – 6:1 |
| Briggs 5HP (Classic) | 206cc | 5.0 HP | 3600 | 2400 | 5:1 – 7:1 |
| Tecumseh 5HP | 148cc | 5.0 HP | 3600 | 2200 | 5.5:1 – 7.5:1 |
| Pocket Bike 47cc | 47cc | 2.5 HP | 7500 | 6000 | 4:1 – 7:1 |
| Honda CRF50 49cc | 49cc | 2.4 HP | 7000 | 5500 | Multi-speed (4-speed) |
| Project | Engine | Drive / Driven | Tire Dia. | Est. Top Speed | Use Case |
|---|---|---|---|---|---|
| Stock Pocket Bike | 47cc 2-stroke | 11T / 68T | 10" | ~20 mph | Flat pavement, kids |
| Baja Warrior Stock | Tecumseh 3HP | 12T / 72T | 12" | ~18 mph | Trail, flat dirt |
| Predator 212 Build | Predator 212 | 12T / 60T | 13" | ~28 mph | All-around fun |
| Speed Go-Kart | GX200 | 14T / 54T | 11" | ~32 mph | Flat track racing |
| Hill Climber | GX200 | 10T / 80T | 14" | ~14 mph | Off-road / hills |
| TAV2 Torque Conv. | Predator 212 | TAV + 12T / 60T | 13" | ~30 mph | Trail, variable load |
| Mini Moto Race | Pocket 47cc | 11T / 55T | 10" | ~28 mph | Flat track racing |
Choosing the right gear for a mini bike has big influence on how it can be rode. High gear provides more top speed, but less torque and power. On the other hand, low gear gives stronger power but limits the top speed.
Like this, the right choice of gear depends on what kind of riding matters most.
How to Choose the Right Gear for a Mini Bike
Commonly used gear for karts are made up of 11 to 12 teeth on the front sprocket, combined with 60 teeth on the rear sprocket. On mini bikes truly common are 11 to 12 teeth front and 72 teeth rear. They form good starting points for each rider that builds or sets his ride.
Good balance between torque and speed presents around 6:1 or 7:1 gear. With a jackshaft on the mini bike it is possible to exactly set the gear. Changing the size of front sprockets also helps to settle troubles more easily.
Using a 12-tooth front sprocket with 60 on the axis, one gets almost 5:1 gear, that works well for karts. Gear with 12 front and 75 rear results in around 6.25:1, which works for small mini bikes. On vehicles with jackshafts, something around 4.3 gear can also work, depending on the build.
A 212cc engine with a 12-tooth front sprocket and 40-tooth back on a 13-inch wheel easily reaches 45 mph. That gear gives the bike a lot of power, without two much tension. For big tires, like 8-inch rim, 5:1 gear is a good option.
Counting the gear is fairly easy. Take the RPM of the axis and multiply by the circumference of the tire in inches. This shows the distance in inches each minute.
Websites with calculators simplify that, enter the tooth counts for front sprocket, jackshaft and rear sprocket, then measure the circumference of the final tire. The tool then shows the final gear and approximate top speed in mph.
One thing to mind is a too small rear sprocket. The engine maybe can not reach enough RPM for good top speed with a 53-tooth rear. Going up to 60 or 65 teeth indeed can give the bike higher top speed.
Many newcomers simply choose parts from what sits in the garage, but a calculator removes the guess from the cause.
Tuning can range depending on the conditions. Stay at one rear sprocket and buy some different sized frontsprockets for exchange is a handy way to try.
