| Mini-Bike Kit: Introduction and Parts Inventory |
From "Weekend Mechanic"
episode WKM-212 |
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In this episode, Weekend Mechanic Bruce Bonebrake builds a classic mini-bike. This is an ideal project for introducing young and potential weekend mechanics to the world of engine work. Mini-bikes can be purchased complete and ready to ride, or you can purchase a kit that you put together yourself. You can purchase kits with -- or without -- the engine included, or you can build a mini-bike from your own selection of parts. Kits and parts are available from specialty manufacturers, and can range in price from about $600 to $2000. For our project, we found a vintage '60s-era mini-bike kit ( figure A), complete with extended front "chopper" forks and "sissy bar." DIY Difficulty Rating for the Project: This project is not complex, and we gave it a rating of 2 on a 5-point intermediate-level scale. Depending on the kit you select, this job might be finished in a single day. Allow yourself a whole weekend, though, to allow for any possible complications, and to allow the kids an opportunity to get involved. Important: Included below are the steps in this mechanical procedure as shown in the episode. These steps are general guidelines that are applicable to most mini-bike kits. With any particular kit, there may be procedures, specifications, settings, tolerances, components, etc. that are specific to that kit. Read and follow the manufacturer's directions and precautions that come with your kit and/or parts. Safety Alert: Always wear eye protection, and follow proper safety precautions, when working with power tools. In addition to standard auto-mechanic's tools, the only specialty tool that will be needed for this project is a grease gun. An air-ratchet is optional, but will help speed the assembly process.
Parts Inventory
- Modern-day upgrades on the vintage kit include:
- Aluminum racing wheels;
- All-terrain tube-type tires;
- 70-tooth racing sprocket (figure B);
- New chain (figure C);
- Throttle assembly, throttle cables and brake lever (figure D);
- Rear-mounted reflector;
- Rear fender;
- New seat (figure E) custom-fit for the sissy-bar design.
- For the drive-train we found a 2-cycle, 8-horsepower racing engine (figure F). It should allow the finished mini-bike to reach speeds of 35 mph.
- A high-performance exhaust system (figure G) incorporates a heat-shield to protect the rider's leg from the heat generated by the engine.
- Since the vintage frame-assembly was made for a 4-cycle engine, a special adapter was located to adapt the kit's frame mount to the connections on the 2-cycle engine.
- The high-performance air- cleaner assembly (figure H) features a reusable air filter. A fuel shut-off valve is mounted to this same assembly. T
- he fuel-tank assembly (figure I) incorporates a fuel filter.
- As a safety feature, a kill-switch (figure J) will be mounted on the hand-grip, enabling the engine to quickly and easily be turned off.
- To stop the mini-bike, a brake band surrounds the outside of the clutch assembly (figure K).
Getting Started
- Begin the assembly by installing the tubes into the tires (figure L).
Tip: It's a good idea to put a small amount of air into the tube before installing it into the tire. The air helps to remove wrinkles and makes it less likely that you'll pinch the tube between the two halves of the wheel before you bolt them together.
- Next, place the wheel in the rear tire. Each aluminum wheel comes in two halves. Place the first half of the wheel into the tire (figure M) making sure to line up the slot on the wheel with the valve-stem on the tube.
Tip: Place a little liquid soap on the bead of the tire before inserting the wheel. This will help the tire pop over the wheel.
- Place the other half of the wheel, making sure the bolt-holes on the two halves line up. Slip a bolt through one of the holes.
- With the two halves of the wheel lined up, slip the sprocket into place (figure N), making sure that it's on the side of the wheel opposite the valve stem.
- Install the lock-nuts and tighten them down.
- The front wheel goes together in the same way -- only without the sprocket.
In the segment that follows, the tires and frame are prepped and the assembly continues.
RESOURCES :
The Haynes Small Engine Repair Manual
ISBN: 1850106665
Author: Curt Choate, John H. Haynes
Haynes Publishing Group
Chilton's Small Engine Repair Up to 20 Hp
Model: 0801983258
Author: Kerry A. Freeman
Nichols Publishing
Go-Kart Racing Chassis Setup
Model: 0960506845
Author: Brian Martin
Martin Motorsports Pub. Co.
International Karting Industry Buyer's Guide
Model: 0966146743
Author: Darrell E. Sitarz
Kart Marketing Association of America
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