125cc Motorized Drift Trike

I built this project over the course of a year back in the 9th grade. I didn't know CAD, so everything was figured out using an entry-level Harbor Freight flux-core welder, a digital caliper, a multimeter, and garage trial and error. The layout was subtly inspired by Colin Furze's YouTube drift trike, but since he didn't leave a blueprint, I had to figure out all the sizing, frame geometry, welding, and hardware constraints on my own.

This guide covers the raw technical details and mistakes so you can build your own successfully.

Core Components

Donor Frame: Razor DXT Drift Trike (Sourced for $30 on OfferUp)

Engine: Lifan 125cc Manual Engine Kit with Carburetor & Harness — $760.00

Drivetrain Axle: Go Power Sports 38" Live Axle Kit (Slick Tires & Disc Brake Option) — $369.06

Rear Axle Sprocket: HIAORS 16-Tooth #428 Drive Sprocket — $9.00 * Sprocket Machining: Professional machine shop labor to bore the center — $50.00

Seating: Universal Metal Flat Tractor Seat — $40.00

Brakes: Left Side Hydraulic Disc Brake Assembly — $32.00 (Heavy-duty scooter/ATV grade)

Controls: Universal Hand Gear Shifter Lever — $13.74

Handlebars: Donor BMX Bike (Sourced for $30)

Fuel Tank: Podoy Mini Pocket Bike Gas Tank — $10.00

Fuel Lines: Dirt Bike Fuel Line Filters and Petcock Valve Kit — $12.00

Gas Vent: Gas tank cap vent valve — $8.00

Safety Flag: 6ft ATV High-Visibility Safety Flag with Pole — $24.00 (It cost me $24 idk why but this one is less)

Raw Materials & Consumables

Chassis Tubing: 20ft Rectangular Mild Steel Tubing — $60.00

Structural Steel: Flat Steel Bar Stock ($59.00 total) & Angle Steel Stock ($14.00)

Welding Wire: 0.030" Gasless Flux Core Welding Wire E71T-GS — $23.00

Chemicals & Compound: JB Weld High-Temp Exhaust System Epoxy — $10.00, Threadlocker Blue 242

Electrical System: 12V Motorcycle Battery ($60.00), Handlebar Start/Kill Switch ($13.00), wire, zip ties, electrical tape

Hardware: Metric M8 hex bolts, 1/4" lock nuts, 3/4"-16 lock nuts, plain steel threaded rod

Total Build Cost: $1,720.44

Design Alternative

Differential Option: If you don't want a completely locked rear live axle, you can adapt a Peerless 100-224 Chain-Driven Differential Assembly. For an explanation on why differentials drastically alter vehicle handling dynamics, check out this educational video breakdown.

Flux-core fumes are nasty, and the welds can pop hot splatter in your eyes even after you're done welding. SO always wear a P100 respirator—the small pancake-sized particulate filters fit best under a welding helmet—and keep safety glasses on underneath your welding mask/shield.

You will spend a lot of time with an angle grinder during this build process for cutting all of your pieces. I started off with a cheap $14 Harbor Freight grinder until that thing eventually exploded on me, then moved on and got a Milwaukee. Grinders are super super loud and dangerous, so safety earmuffs and goggles are a total necessity.

If it’s your first time using an angle grinder, you have to be careful because the cut-off discs can explode on you quite often or get stuck in the metal. Do not twist or tilt things around while you are cutting. Just try to keep it perfectly straight, apply a light amount of pressure, keep the grinder guard on your tool, and wear your safety glasses. You'll be all right, and the rest you'll learn with time and probably still have all of your fingers.

Before laying out the frame, you need to decide how you want the rear end to handle, because a 125cc engine completely changes the physics of drifting. You have three main paths to consider here (I wish I knew this ):

Path A: Solid Live Axle with Bare Rubber Slicks (What I Used)

I opted for a completely solid live axle running bare racing go-kart slick tires. Because a solid axle locks both rear wheels together, they are forced to spin at the exact same speed. When you dump the clutch on a 125cc motor, the massive torque easily breaks the traction of bare rubber slicks from a dead stop. This setup gives you an incredibly aggressive, high-speed drift that feels planted but slidey, and it lets you hook up and catch traction instantly when you straighten out.

Path B: Solid Axle with PVC Sleeves

Traditional pedal drift trikes use thick plastic PVC sleeves slid over the rear tires to take away all traction. If you run PVC sleeves on a high-horsepower 125cc trike, you will slide around at the slightest touch of the throttle. However, because the plastic offers almost zero rolling resistance, the engine will easily bounce off the rev limiter, your braking distance will skyrocket, and the sleeves can wear down or crack rapidly under engine-driven friction.

Path C: Open Differential Configuration

If you do not want a locked rear axle, you can adapt a Peerless 100-224 Chain-Driven Differential. An open diff allows the outside wheel to spin faster than the inside wheel during a turn, making ordinary cruising and tight maneuvering incredibly smooth. The trade-off is that it can make initiating a controlled drift harder, as power naturally travels to the wheel with the least amount of resistance. This video breaks down why differentials alter vehicle handling dynamics.

A 125cc pit bike engine has immense low-end torque. A standard, massive go-kart rear sprocket will hit your frame or scrape the ground constantly.

To preserve clearance, configure a 1:1 final gear ratio. I matched a 16-tooth front sprocket to a tiny 16-tooth rear sprocket. The internal sequential gearbox handles the torque in low gears, and the compact rear sprocket size keeps your ground clearance safe while allowing a 50+ mph top speed.

Finding a 16-tooth rear sprocket built for a 1-inch keyed live axle is nearly impossible. I bought a cheap motorcycle front engine sprocket and had a machine shop lathe-bore the center to a 1-inch slip fit using carbide tooling for $50. Do not try to drill hardened steel yourself.

To bypass cutting an expensive keyway slot into the hardened sprocket:

1. Slide the bored sprocket onto your 1-inch live axle.
2. Sandwich it tightly between two standard 1-inch keyed shaft collars.
3. Install the keys into the axle keyway directly underneath the collars and clamp them down.
4. Flux-core weld the sprocket directly to the mild-steel faces of the shaft collars on both sides.

The keys in the collars transfer the rotational torque to the axle without needing a broaching tool.

For chain tensioning, elongate your lower frame engine mount holes into adjustment slots by tilting your drill bit back and forth. This lets you physically slide the engine forward to take up chain slack before tightening your M8 mounting bolts. You can also add a cheap spring-loaded chain tensioner to handle dynamic chain slap.

On my first try, I tacked a frame together, dropped the engine in, and found the output shaft completely misaligned with the rear axle. I had to chop the whole thing apart and restart.

To fix this on the second attempt, I fixed the axle location on my stand, set the front fork out, and used heavy-duty ratchet straps hanging from the ceiling to suspend components in mid-air. I also used "Cardboard Aided Design" (CAD)—mocking up custom mounting tabs and plate locations out of cardboard and masking tape to hold objects in place and visualize clearances before cutting steel.

The biggest mistake I made here was mocking up the frame with the front wheel pointing dead straight, leaving a flat 1.5-inch ground clearance. I forgot to account for the steering geometry's caster angle. When you turn a raked front end, the fork geometry swings out, causing the nose of the chassis to drop down. My 1.5 inches of clearance dropped to under half an inch during tight turns, causing the bottom frame steel to scrape the asphalt on hard corners. Make sure you angle your front frame rails slightly upward as they travel forward to absorb this steering droop.

Aftermarket pit bike engine harnesses assume they are being re-installed onto a factory dirt bike frame with complete electrical accessories.

These modular harnesses include integrated circuits for headlights, taillights, and handlebar switches. When building a stripped-down, bare-metal trike with no lights, the safety circuit remains open and the ignition system will refuse to spark.

To fix this, use a multimeter to check continuity across the harness plug. Locate the power supply loop meant for the lighting switch and install a permanent wire bridge jumper across the terminals. This tricks the CDI box into thinking the entire accessory circuit is closed and active, instantly sending spark to your plug.

For wire management, use plenty of electrical tape and zip ties. I drilled holes through non-structural sections of the frame to route large zip ties through to hold the relay switch and components clean. Always clean a patch of frame down to raw steel with an angle grinder to bolt your negative ground wire directly to the chassis.

Engine Break-In Note: Brand new engines often contain fine metal dust or machining burrs inside the crankcase from the factory. Completely drain and change the oil after the first 5 hours of riding to protect your transmission gears.

Standard bicycle brakes will not stop a 125cc trike going over 50 mph. I used a heavy-duty hydraulic disc brake assembly designed for Vespa scooters and heavy ATVs.

High-frequency engine vibrations on a rigid, suspensionless frame can cause your axle keys to walk out of their slots if your hardware isn't locked down. On a test run, my brake rotor key slipped out. When I pulled the brake lever, the caliper clamped the disc perfectly—but the axle kept spinning freely inside the hub, leaving me with zero brakes. I had to slow down by jamming my shoes into the front tire.

To guarantee this never happens, always sandwich your brake hub, your driven drive sprocket, and your wheel hubs between two locked shaft collars on both sides. Physically capping both open ends of the keyway channel mechanically traps the key inside its slot.

Because the vibrations are extreme, every single safety-critical bolt needs split-lock washers, blue threadlocker, or Nyloc nuts. If you use Nylocs, make sure the bolt threads fully bite into and extend past the plastic locking ring. One of my 3/4-inch rear wheel axle nuts vibrated off on a test drive—if the tire had come off at speed, it would have been catastrophic. Check your hardware constantly.

If you weld your engine cradle completely shut, doing basic top-end engine maintenance or swapping parts turns into a nightmare where you have to cut your frame apart. To solve this, design the upper frame crossmember—the part holding the top central bolt of the engine—to be completely removable. Weld heavy mild steel mounting flanges to the main chassis rails and secure the crossmember with high-tensile bolts. If you ever need to pull the engine, just unbolt this arm and slide the powerplant free.

Another major trap I encountered was mounting my heavy 12V battery box beneath the frame rails. I welded plain hardware store threaded rod directly to the frame to act as mounting studs. However, the threaded rod was nickel-plated/galvanized. Welding plated fasteners directly to a mild steel frame with flux-core wire creates an incredibly brittle metallurgical joint. Under the intense vibrations of the engine, the studs cleanly snapped off at the base, sending my battery tray crashing onto the road at high speed. Never weld plated hardware. Always use an angle grinder to strip coatings down to bare, raw steel, or stick strictly to plain, uncoated mild steel studs. For extra safety redundancy against vibration, you can use strong velcro straps or large zip ties to hold the battery securely in place.

Lastly, the stock dirt bike exhaust is bent to route high along a bike frame, which would have pointed hot piping directly at my legs or tractor seat. I tried heating up the pipe with a torch to bend it, but that doesn't work well for aggressive, short-length bends that you need to exaggerate. Instead, use an angle grinder to slice the exhaust pipe into sectioned, wedged pieces, rotate them to navigate a low path under the seat, and weld them up with as few pieces as possible to get the angle you want. I had to shorten my exhaust a good amount. Also, do not let the full weight of a heavy muffler hang off the engine exhaust manifold studs; the leverage and vibration will snap the manifold bolts. Fabricate a dedicated steel bracket in the back to support the muffler canister directly to the rear square frame tubing, and use high-temp exhaust epoxy to cleanly seal any slip joints.

So far, this project has been the most exciting and fun thing I have ever personally worked on as a personal project. Making it was an absolute blast. I loved working with metal. It was frustrating at times because I didn't plan everything out in CAD, so if you do have that luxury and skill, I totally recommend you do that. But also, don't worry about planning too much. As long as you get the general frame geometry right, that's what matters.

One thing I'd definitely emphasize is I didn't really think a whole lot about the logistics going into this project and how useful or practical this bike would be, but honestly, I had so much fun ripping this thing around in my neighborhood with my friends, and it was just an absolute blast. I got to learn so much about metal working. It was totally worth it, so one thing I would say is that if you're thinking about doing a project, it doesn't even have to be specifically this—just go for it, give it a shot. Don't think too much about it because just the joy of making things alone is a good justification for building something.

Once you're done building this thing, you'll notice it is easily the most exciting, exhilarating, and adrenaline-pumping thing you have ever driven. The raw noise of the engine is incredible—you can physically feel it, and shifting with your hand makes it feel even more intense. It's kind of like if a go-kart, a suicide shifter, and a dirt bike all had a baby.

It is just insane how fun this thing is to ride. Just going through that sequential transmission, not having to worry about a clutch lever on your handlebars, but having all of the fun of the gears is awesome. Just be careful when you first build this thing because it is an absolute monster, and you have to learn how to tame it. Overall, have fun, and feel free to take this thing to a big open parking lot or maybe a gravel area where you can lose some traction, and just rip around!