1. What is a Mini Bike Speed Calculator W/ Jackshaft?

Definition: This calculator estimates the speed of a mini bike that uses a jackshaft system based on engine RPM, tire diameter, and gear ratios.

Purpose: It helps mini bike enthusiasts and mechanics determine the theoretical top speed of their mini bike configuration.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR1 \) — Primary gear ratio (engine to jackshaft)
• \( GR2 \) — Secondary gear ratio (jackshaft to wheel)

Explanation: The formula calculates how fast the bike moves based on how quickly the engine turns, the gear reductions, and how far the bike travels with each wheel rotation.

3. Importance of Speed Calculation

Details: Proper speed estimation helps in gear ratio selection, performance tuning, and ensuring the bike operates within safe speed limits.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter in inches, primary gear ratio (engine to jackshaft), and secondary gear ratio (jackshaft to wheel). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a jackshaft?
A: A jackshaft is an intermediate shaft that allows for additional gear reduction between the engine and rear wheel.

Q2: How do I find my gear ratios?
A: Primary ratio = engine sprocket teeth ÷ jackshaft input teeth. Secondary ratio = jackshaft output teeth ÷ wheel sprocket teeth.

Q3: Why 1056 in the formula?
A: This constant converts inches per minute to miles per hour (12 inches/foot × 5280 feet/mile ÷ 60 minutes/hour).

Q4: Is this the actual speed I'll get?
A: This is theoretical speed. Actual speed may vary due to factors like rider weight, terrain, and mechanical efficiency.

Q5: How can I increase my mini bike's top speed?
A: Options include increasing RPM, using larger tires, or reducing gear ratios (smaller engine sprocket or larger wheel sprocket).