Secure the chainsaw engine, use a clutch and jackshaft, and gear it down.
Curious about turning a garage find into a wild little ride? You’re in the right spot. I’ve built, broken, and rebuilt enough mini bikes to know what works. This guide shows how to put a chainsaw motor on a mini bike the right way. I’ll keep it simple, safe, and real. If you want to learn how to put a chainsaw motor on a mini bike without wasting time or parts, read on.
Safety, legality, and feasibility check
Before we wrench, let’s make sure this is worth your time. Chainsaw engines are light, loud, and rev happy. They make decent power for their size, but they need smart gearing and a safe setup. If you want to know how to put a chainsaw motor on a mini bike, start with this checklist.
- Wear gear. Use eye protection, gloves, ear protection, and boots.
- Use working brakes. A rear disc or drum in good shape is a must.
- Keep the guard on. A chain guard is not optional.
- Know the laws. This is an off-road build in most places.
- Be honest about tools. A welder helps. A drill, files, and a grinder are needed. You can do bolt-on, but it takes patience.
- Expect to tune. Two-stroke engines need proper fuel mix and carb tuning.
I learned this the hard way with my first 50cc saw swap. It ran fast, then ate a chain because I skipped alignment. Slow down and plan. That is how to put a chainsaw motor on a mini bike that lasts.
Tools and parts you will need
You can build this with basic tools and a few key parts. Here’s what I use when I show friends how to put a chainsaw motor on a mini bike.
- Chainsaw engine. 35–60cc is common. Keep the flywheel shroud for cooling.
- Steel for the mount. 1/8 to 3/16 inch plate and angle steel.
- Fasteners. Grade 8 bolts, washers, and Nylock nuts.
- Jackshaft kit. Shaft, bearings, hangers, and two sprockets.
- Clutch. A centrifugal clutch sized for the final drive or jackshaft.
- Sprockets and chain. #35, 415, or 420 chain is common on mini bikes.
- Throttle cable and return spring. Use a real mini bike throttle.
- Kill switch. Bar-mounted, wired to ground the coil.
- Fuel system. Stock tank or a remote tank, fuel line, and filter.
- Alignment tools. Straightedge, calipers, and a chain breaker.
- Optional rubber isolators. To cut vibration at the mount.
Tip: If the saw has a tapered crank, you may need an adapter or use the saw’s clutch drum as a drive drum with a custom sprocket. That detail often decides how to put a chainsaw motor on a mini bike without machine work.
Plan your layout and gear ratio
Two-strokes make power at high rpm but low torque. Gearing fixes that. If you want a smooth, strong launch, plan the ratio before you cut steel. This is the math I use when teaching folks how to put a chainsaw motor on a mini bike.
- Target wheel rpm. A 10-inch tire at 20 mph turns about 675 rpm.
- Engine rpm. Many saws make power near 7,000–9,000 rpm under load.
- Ratio needed. 9,000 ÷ 675 ≈ 13.3:1 overall reduction.
- Use two stages. A jackshaft lets you do something like 4:1 then 3.5:1.
Practical gear pairs that work:
- Engine/clutch sprocket to first jackshaft sprocket: 10T to 40T.
- Second jackshaft sprocket to rear wheel: 12T to 42T.
- Mix and match to land near 12:1 to 15:1.
This is the heart of how to put a chainsaw motor on a mini bike that does not bog or grenade chains.
Build a solid engine mount
A stiff mount keeps the chain happy and the ride smooth. Here is a simple method that works.
- Mock the layout. Set the engine where the exhaust and pull starter clear everything.
- Cut a plate. Match the engine base. Slot the holes for chain tension.
- Brace it. Weld or bolt angle steel legs to the frame rails.
- Add gussets. Small triangles stop flex.
- Test fit the chainline. Use a straightedge from the clutch to the rear sprocket or jackshaft.
I like to use rubber washers between the plate and frame to cut buzz. Not too soft. You want strength first. This is a key step in how to put a chainsaw motor on a mini bike safely.
Choose and fit the drive system
This is where most builds get stuck. Chainsaw cranks are often tapered. Mini bike clutches want a straight, keyed shaft. You have three common paths.
- Use the saw’s stock clutch drum. Weld or bolt a compatible sprocket to the drum. Then run a chain to the jackshaft.
- Use an adapter. Some small-engine suppliers sell taper-to-key adapters. Then you can fit a standard clutch.
- Belt to jackshaft. Run a small belt pulley from the saw clutch drum to the jackshaft. Then chain to the wheel.
Key tips:
- Keep the first reduction big. It saves chains and clutches.
- Choose a clutch engagement rpm close to the engine’s torque peak.
- Shield moving parts. Guard the clutch and the first chain or belt.
Getting this right is at the core of how to put a chainsaw motor on a mini bike without headaches.
Fuel, throttle, kill switch, and cooling
Most chainsaw carbs are diaphragm types. They can pull fuel from odd positions, which helps. Still, clean plumbing matters.
- Fuel. Fresh premix at 40:1 or as the engine maker states.
- Tank. Use the stock tank or a small remote tank above the carb.
- Filter. Inline filter keeps jets clean.
- Throttle. Use a proper throttle cable and add a return spring at the carb.
- Kill switch. Wire the bar switch to ground the ignition lead.
- Cooling. Keep the flywheel fan shroud. Do not cover the intake inlet.
A stable idle and crisp throttle make it feel factory. This is a quiet win when you figure out how to put a chainsaw motor on a mini bike that rides day after day.
Align the chain, add brakes and guards
A straight chainline saves lives and chains.
- Align first stage. Match sprockets within 1 mm with a straightedge.
- Set tension. About 1/2 inch of slack on the longest span.
- Lube. Use chain lube after every dusty ride.
- Brakes. Adjust before first fire-up. Test at low speed.
- Guards. Cover the clutch and chain to keep clothes and fingers safe.
I once skipped a guard on a test roll. A hoodie string caught the chain. Never again. If you want to master how to put a chainsaw motor on a mini bike, respect the guards.
First start, tuning, and test ride
This is the fun part. Take it slow.
- Prime and start. Choke on, pull start, then open the choke.
- Tune idle. The chain should not creep at idle. Lower clutch engagement or idle as needed.
- Adjust mixture. Two-strokes like a bit rich on the high side for cooling.
- Heat cycle. Let it warm, cool, then recheck bolts and chain.
- Short runs. Try 5–10 mph first. Check temps, brakes, and chain.
Keep notes. Small turns on the needle screws matter. This attention to detail is how to put a chainsaw motor on a mini bike that runs clean and cool.
Troubleshooting and common mistakes
Every build throws curveballs. Here are fixes I use and teach.
- Chain jumps off. Check sprocket alignment, add a guide, and increase wrap on small sprockets.
- Bog on launch. More reduction. Try a bigger driven sprocket on the jackshaft or wheel.
- Overheating. Clear the shroud. Richen the high-speed screw slightly.
- Slipping clutch. Raise engagement rpm or increase first-stage reduction.
- Vibration cracks. Add gussets to the mount and use fresh, balanced sprockets.
If you hit a wall, step back and recheck the ratio. Gearing is 80% of how to put a chainsaw motor on a mini bike that feels right.
Frequently Asked Questions of how to put a chainsaw motor on a mini bike
Is a chainsaw engine strong enough for a mini bike?
Yes, for light riders and flat ground. A 35–60cc saw can move a small bike if you gear it down well.
What gear ratio should I start with?
Aim for 12:1 to 15:1 overall. Adjust by rider weight, tire size, and terrain.
Can I use the chainsaw’s stock clutch?
Often yes, by adapting the drum to a sprocket or pulley. Many builders run that to a jackshaft for more reduction.
What chain size should I use?
Use what your sprockets support. #35, 415, or 420 work well on mini bikes and hold up to abuse.
Do I need a jackshaft?
It helps a lot. It lets you run two-stage reduction and place the chain where it clears the frame.
How do I keep the engine cool?
Keep the fan shroud and air inlets clear. Do not box the engine in, and tune slightly rich on the high-speed needle.
Is this street legal?
Usually no. These builds are for off-road use. Check your local rules.
Conclusion
You now know how to put a chainsaw motor on a mini bike from plan to first ride. Start with safety, pick smart ratios, and build a stiff mount. Use a jackshaft, align the chain, and tune rich enough to keep it cool. That is how you turn a loud little engine into a smooth, usable bike.
Ready to try it? Save this guide, make your parts list, and sketch your gear ratio tonight. Share your build, ask questions, or subscribe for more small-engine tips.
