Zip around your property or nearby trails on the fun and rugged Coleman CT100U 105cc mini bike. This compact motorcycle packs surprising power into a small, lightweight package perfect for recreational riding. The Coleman 105cc engine offers plenty of torque to climb hills and traverse uneven terrain. With fat knobby tires and a flexible frame, it handles bumps and dips with ease. Read on to learn all about the features, performance, maintenance, and modifications for this iconic American mini bike.
Overview of the Coleman CT100U 105cc Mini Bike
Coleman Powersports introduced the 105cc CT100U trail mini bike in the early 2000s as an upgrade over their popular 80cc models. The company wanted to offer improved power and hill climbing ability in response to customer demand.
The CT100U utilizes a 105cc 4-stroke air cooled single cylinder engine designed and built by Coleman. This provides a noticeable bump in speed and acceleration over smaller 80cc motors. The engine feeds into a manual clutch and 3-speed transmission allowing you to find the right gear for terrain and speed. Top speed from the factory is around 25 mph on flat ground.
Key specs and features of the Coleman 105cc mini bike include:
- 105cc air cooled 4-stroke OHV engine
- Up to 25 mph top speed
- 3-speed manual transmission
- Front and rear drum brakes
- Single seat
- 17 inch knobby tires
- Tubular steel frame with front suspension
- Kick start
- Rear rack and grab bar
- Available in red or yellow color options
With fat tires, flexible suspension, and gobs of torque, the Coleman 105cc CT100U is ready for off-road fun right out of the box. Its rugged construction withstands the bumps and spills of trail riding. The 105cc motor offers noticeable gains in acceleration and hill climbing versus smaller engines. Let’s look closer at the performance and handling.
Engine Performance and Power
The heart of the Coleman 105cc mini bike is the single cylinder 4-stroke engine. This air cooled motor utilizes an overhead valve (OHV) cylinder head design for good airflow and combustion efficiency. The bore and stroke measure 52mm x 49.5mm.
Feeding the engine is a factory jetted slide type carburetor with throttle cable and air filter. Exhaust exits through a muffler located on the right side of the bike. Ignition is provided by a flywheel magneto CDi system. There is both kick and electric start on most models.
The Coleman 105cc engine is rated to produce around 5.5 horsepower at 7000 rpm. While not hugely powerful, it has quite muscular torque right off idle. This allows the mini bike to accelerate well from a standstill and power up steeper hills. The engine pulls strong through all three gears, with a top speed around 25 mph.
For a mini bike the CT100U 105cc has great off-road manners. It can traverse bumpy trails, muddy patches, and hills without bogging down thanks to the healthy low-end power. Just be aware the suspension is somewhat limited, so true high speed rough riding is best avoided. For recreation around the farm, acreage, or mellow trails, the 105cc motor hits the sweet spot.
Clutch, Transmission, and Gearing
Shifting duties on the Coleman 105cc mini bike are handled by a 3-speed manual transmission with centrifugal clutch. This setup balances good acceleration with a top speed fitting the bike’s intended use.
The clutch uses weights and springs to engage cleanly when the engine rpm rises after starting. This eliminates the need for a clutch lever while still allowing control. The clutch improves low speed riding and climbing loose surfaces where momentum is key. A tuning screw provides adjustment if needed.
Power routes through the 3-speed transmission using a hand operated gear shifter on the left side of the bike. Gears are selected sequentially. The ratios give a good blend of low end grunt and higher speed legs. Most riding can be done in 2nd gear, with 1st providing extra torque for hills and 3rd for maximum speed.
The gearbox feeds back to the rear wheel via #420 chain drive. A 13 tooth front sprocket and 33 tooth rear sprocket give appropriate overall gearing for the 105cc motor. The setup is geared well for off-road and allows the engine to stay in its power band. Stock gearing enables a top speed of around 25 mph flat out in 3rd gear.
Chassis, Suspension, and Handling
The Coleman 105cc CT100U utilizes a basic but functional steel tube chassis to support the engine and drivetrain components. The main frame uses round tubing to create the cradle holding the engine and fuel tank. A single backbone tube routes rearward to a loop supporting the seat and rear fender.
Suspension duties are handled by a pair of basic coil over shocks. An adjustable preload spring shock absorbs impacts up front in the single downtube. The rear swingarm utilizes a similar coil spring and tube shock. Suspension travel is around 2-3 inches at both ends. While somewhat limited, it smooths out smaller bumps and trail chop nicely.
Slowing down the fun is handled by front and rear drum brakes activated by handlebar levers. Stopping power is adequate for the mini bike’s size and speed. The rear brake is mounted in the left side case, geared off the countershaft.
Moving forward, the 17 inch knobby tires provide decent grip on loose dirt. They are mounted on 8 inch steel wheels front and rear. Handling is nimble with the narrow profile tires and 35.5 inch wheelbase. The CT100U can whip around and is fun to toss into corners. Just take care not to exceed the limited traction and suspension capabilities.
Additional CT100U 105cc Mini Bike Features
Besides the engine and chassis, Coleman packed a few other handy features into their 105cc trail machine:
- Electric & Kick Start – Option of kick starting using the fold out lever or push button electric start when equipped. The starter motor is actuated by a button on the handlebars.
- Throttle Limiter – A removable screw limits throttle input for beginning riders. This prevents accidental full throttle operation before younger riders are ready. Easily removed later.
- Front Rack – The tubular front rack gives carrying capacity for small loads or strapping down items. Nice for transporting lunch or tools out on the trail. Rated for 15 lb capacity.
- Rear Grab Bar – The rear looped grab bar gives a secure handhold for a passenger seated on the rear fender. Always use caution carrying a passenger.
- Fuel Shutoff – The valve under the tank lets you shut off fuel when transporting or storing the mini bike to prevent leaks.
- Chain Guard – A metal cover encloses the upper chain run helping keep clothing and body parts away from the fast moving chain.
- Foldable Foot Pegs – The OEM foot pegs can fold up when needed to further reduce width. Helps fit through narrow gaps or for storage.
Along with the engine performance, these useful features expand the CT100U 105cc versatility and functionality. Now let’s go over some key maintenance and service items.
Routine Maintenance and Service Items
Like any motor vehicle, following the manufacturer’s maintenance schedule is important for keeping your Coleman 105cc mini bike running safely and reliably. Here are some of the key regular service items:
- Oil Changes – Drain and replace the engine oil every 20-30 hours of use. Use 10w-40 or similar viscosity mini bike oil. Change oil filters as specified.
- Air Filter – The foam air filter element should be cleaned and re-oiled every 15-20 hours to allow proper airflow. Replace annually or when damaged.
- Spark Plug – Replace the spark plug each year or at 50 hour intervals. Use an NGK BR6HS or equivalent plug gapped to 0.028-0.031 inches.
- Chain – Lubricate the drive chain every few rides using chain lube or gear oil. Adjust chain tension as needed.
- Cables – Lubricate the throttle and clutch cables periodically using a spray cable lube. Check for damage and replace if frayed or kinking.
- Brakes – Inspect brake shoes for wear and adjust as needed. Make sure the drums are clean and smooth. Check brake fluid level in the master cylinder.
- Nuts & Bolts – Check and tighten any fasteners that may have vibrated loose. Pay particular attention to the engine mounts, suspension pivots, and wheel lug nuts.
- Tires – Verify tire pressure is around 10 PSI. Inspect tread depth and replace tires as required. Check for cracks, dry rot, or signs of damage.
Following the maintenance schedule keeps the mini bike running safely and prevents more costly repairs down the road. Be sure to use OEM or equivalent replacement parts to maintain proper fit and durability.
Common Upgrades and Modifications
One of the joys of owning a Coleman CT100U 105cc mini bike is customizing it to suit your needs and style. Here are some popular upgrades mini bike enthusiasts perform:
- Stage 1 Kit – Easy bolt-on kit increases airflow and fuel delivery for 7-10% more power. Includes intake, exhaust, and rejetted carb.
- Big Bore Kit – Increase displacement to 112cc or 121cc for even more torque and speed. Requires some engine teardown.
- Suspension – Upgrade front forks to coil or hydraulic units. Add longer travel rear shocks for improved ride.
- Wheel & Tires – Switch to bigger 19″ rear wheels and add aggressive dirt bike tires for traction.
- Brakes – Improve stopping power by upgrading to hydraulic disc brakes front and rear.
- Gearing – Change sprockets to alter gear ratios – lower for acceleration or taller for high speed.
- Air Filter Kit – Add an oiled foam filter element and intake for better airflow.
- Throttle Limiter – Remove the throttle restricting screw for full speed operation.
- Kill Switch – Wiring in a handlebar kill switch provides an emergency shut off while riding.
- Handlebars – Install wider bars or add bar ends for improved steering control.
- Lighting – Upgrade the lighting with brighter bulbs, LEDs, or small auxiliary lights for riding at dusk.
Always check that any modifications you perform are legal and safe. Certain engine upgrades may impact reliability or longevity if taken too far. But mild performance mods and handling improvements can take your Coleman 105cc to the next level.
Finding Parts and Accessories
The Coleman 105cc mini bike remained mostly unchanged for many years, which makes finding parts and accessories fairly straightforward:
- Coleman Parts – Order direct from the Coleman Powersports website. They stock original equipment parts for the engine, drivetrain, chassis, bodywork, etc.
- Aftermarket Parts – Many general mini bike parts and components fit the 105cc Coleman with little or no modification. Try retailers like Gopowersports, BMI Karts, and OMB Warehouse.
- salvage Yards – Check with local powersport salvage yards to locate used parts and take-off components at reduced cost. Great for body panels and some hard to find items.
- eBay Motors – Huge selection of new OEM and aftermarket parts listed daily by reputable sellers. Sort by fits Coleman 105cc.
- Mini Bike Forums – Connect with the mini bike community to find parts for sale or get guidance on modification projects. Active forums include ColemanTalk, Mini Bike Forum, and pocketbikeplanet.
- Facebook Groups – Mini bike enthusiast groups like Coleman Mini Bikes and Coleman CT200U Mini Bike Club are another good source for parts and accessories.
Having a source for spare parts ensures you can keep your classic Coleman 105cc trail machine running for years to come. Even as Coleman phases out mini bike models, the huge supply chain and enthusiast market keep replacement parts readily available.
Common Problems and Solutions
As with any motor vehicle, issues can occasionally arise on the Coleman 105cc mini bike. Here are some common problems and potential solutions to be aware of:
- Engine misfires or cuts out – Check spark plug, replace if fouled. Inspect wire connections. Clean carb jets if dirty.
- Knocks or rattles during operation – Listen for location; check engine mounts, chain tensioner or sprockets if drivetrain noise.
- Overheating issues – Clean cooling fins if clogged with debris. Make sure oil level correct. Possible head gasket failure if persistent.
- Throttle sticking or sluggish – Lubricate throttle cable using spray lube. Adjust cable tension if needed. Replace damaged cable.
- Brakes ineffective or feel spongy – Replace worn shoes or pads. Check master cylinder fluid level. Bleed system of any air bubbles.
- Hard starting or won’t start – Verify fuel valve is ON. Check for spark. Clean carb jets. Replace spark plug. Possibly low compression.
- Excessive oil consumption – Have engine compression and cylinder head gasket checked. Make sure oil is at proper level.
- Leaking fluids – Inspect gaskets, seals for damage or deterioration. Tighten hose clamps or fittings if loose.
Watching for developing issues and addressing them promptly reduces more extensive repairs down the road. For stubborn problems, don’t hesitate to utilize a qualified small engine or powersports technician.
Finding Service and Technical Support
While home mechanics can handle much of the regular maintenance on a Coleman mini bike, sometimes professional service is required. Here are some options if you need repairs or technical support beyond your mechanical abilities:
- Coleman Support – Contact Coleman Powersports customer support online or call for troubleshooting help. Their technicians can assist with installation questions and warranty issues.
- Local Motorcycle Shop – Many motorcycle service shops work on mini bikes as well as full size machines. Find one familiar with mini bike basics.
- Powersports Technician – Take your mini bike to an experienced powersports mechanic at a dealership, service center or independent shop.
- YouTube Tutorials – Find detailed mini bike repair videos to walk you through many DIY service procedures and mods.
- Forums – Post questions on Coleman owner forums to get advice from fellow riders who have likely addressed the same problem before.
- Service Manual – Purchase a CT100U factory service manual online for step-by-step repair instructions and specifications.
Don’t attempt repairs beyond your skill level. Improper work or assembly can create safety risks. The small engine experts at a powersports shop have the know-how to diagnose and fix almost any issue.
Owning and Enjoying Your Coleman 105cc Mini Bike
Few small motorcycles deliver as much fun per dollar as the classic Coleman 105cc mini bike. With proper care and maintenance, a CT100U provides years of trail riding enjoyment. Run in stock form or customize it to your needs. Finding parts is easy thanks to the huge supply chain. And repairs are straightforward for any DIYer with mechanical skills. The 105cc engine hits a sweet spot of usable power in a nimble and lightweight package. Stay safe, ride responsibly, and enjoy the memories made exploring trails on your Coleman minibike.
