How Do You Make a Mini Motorcycle Faster?

Mini motorcycles are miniature versions of larger models.

Mini motorcycles are manufactured with engines as small as 50 cc for street models, and as large as 100 cc and up for dirt bikes and road racing models. Standard size motorcycle engines have greater tolerances that lend to a number of engine modifications, such as boring the cylinders for oversize pistons. But the reduced tolerances of mini motorcycle engines limit these types of modifications. Short of sending the engine out for a complete blueprint rebuild, you can make a mini motorcycle faster by changing the drive gearing ratio and boosting the engine compression.

Things You'll Need

• Metric wrenches
• Metric sockets and ratchet
• Torque wrench

Instructions

1. Use a metric wrench to loosen the tension adjustment on the drive chain. Lift the chain off the rear wheel sprocket and count the number of teeth on the sprocket. For a higher top-end speed, install a sprocket that has fewer teeth and include a shorter chain.

2. Use a metric socket and ratchet to remove the bolts that mount the original rear sprocket to the rear wheel hub. Attach the smaller sprocket to the hub using the original bolts. Remove the cover on the front sprocket at the side of the engine. Remove the stock chain and install the shorter chain on the front and rear sprockets. Adjust the chain tension to 1/4-inch deflection up and down.

3. Remove the necessary components, such as the fuel tank and radiator, to provide access to the rocker arm valve assembly and cylinder head. Use a socket and ratchet to remove the head bolts. Remove the rocker arm valve assembly and cylinder head intact.

4. Send the rocker arm valve assembly and cylinder head to an engine machinist. Have the head milled .001 an inch to boost the engine compression and add low-end power. Install a new head gasket and install the milled cylinder head and rocker arm valve assembly on the engine.

5. Refer to the owner's manual for torque specifications and use a torque wrench to tighten the head bolts. Reinstall any removed components to complete the upgrade. Test drive the mini motorcycle and expect to experience more power and higher top-end speed.

Tips & Warnings

• Consult a motorcycle specialist for suggestions regarding larger carburetor jets.

References

• MotorcycleAnchor.com: How to Understand Motorcycle Sprocket Math & Drive Ratios
• Motorcycle USA: 2006 SDG Speed Mini Specifications