How to Convert Your Pit Bike to Electric Start

Yes, you can convert most pit bikes to electric start. The key is fitting a starter motor, a ring gear (or a sprag clutch), a small 12V battery, and the right wiring into your existing engine case and frame. This guide covers the most common pit bike engines — horizontal-shaft clones of Honda GX160/GX200 — which make up the vast majority of aftermarket and stock pit bikes.

Engine Compatibility – What You’re Working With

Before buying parts, confirm your engine type. Most pit bikes use 125cc to 160cc 4-stroke horizontal-shaft engines with a side-mounted magneto flywheel. These engines fall into one of three groups:

• Kick-start only – No e-start provisions at all.
• Pull-start only – Common on budget pit bikes.
• Pre-drilled for e-start – Some Chinese engines have threaded holes on the flywheel side but no starter installed.

Measure two things before ordering a kit: the flywheel diameter (most are 60–70 mm) and the crank taper size (the standard is 3/4 inch). If your engine has a different taper — say 1 inch on some larger clones — a standard kit will not fit. Also check whether the engine case has a flat boss near the flywheel cover. If it does, you can often drill and tap it to mount a starter bracket. If the case is aluminum and you find no threaded holes, you can drill and tap M6 or M8 holes using the bracket as a template.

Branch point: If the case is cast iron (rare on pit bikes but possible on older models), drilling is much harder and you’re better off buying a pre-fabricated steel bracket that clamps around the case. And if you see any cracks or warping near the mounting area, stop — that’s a sign to replace the engine rather than attempt a conversion.

Parts and Tools You’ll Need

A typical conversion kit for a Honda GX160/200 clone includes:

• Starter motor – 12V, generic unit with mounting bracket
• Starter ring gear – Bolts to the existing flywheel or replaces it entirely
• 12V battery – 4–7 Ah sealed lead-acid or lithium (must fit in your frame space)
• Solenoid (relay) – 12V continuous-duty, preferably with a built-in fuse holder
• Wiring harness – Pre-made for the kit, or build your own with 14 AWG wire, ring terminals, and a switch
• Start button – Handlebar-mounted momentary switch
• Charging system – If your engine has a lighting coil (typically 2–3 yellow wires from the stator), add a regulator/rectifier to charge the battery; otherwise you’ll need to charge it manually
• Tools – Socket set, Allen keys, wire stripper/crimper, drill and tap set, multimeter, heat shrink, zip ties

Total cost runs $60–$120 for a complete conversion kit, plus the battery.

Step-by-Step Installation

1. Remove the Flywheel Cover and Flywheel

Unbolt the left-side engine cover (the one with the cooling fan and starter cup if you have a pull start). Remove the flywheel nut using a flywheel puller — a standard slide hammer or a dedicated puller prevents damage to the crank taper. Once the flywheel is off, inspect the keyway and the taper surface. If the taper has burrs, clean them with a fine file. Do not reuse a flywheel that wobbles on the crank.

2. Install the Starter Ring Gear or New Flywheel

If your kit includes a ring gear that bolts over the existing flywheel, position it and tighten the included bolts to spec. If the kit replaces the flywheel, install the new one the same way: align the key, slide it on, and torque the nut to 30–40 ft-lb (check your kit’s instructions for the exact value).

3. Mount the Starter Motor

Hold the starter in place so its gear meshes cleanly with the ring gear. Mark the hole positions, drill pilot holes, then tap the case (typically M6 or M8). Use thread locker on the bolts. If the gear doesn’t engage fully, you can add thin washers between the starter bracket and the case to shim the alignment.

4. Install the Solenoid and Battery

Mount the solenoid near the battery but away from exhaust heat. The battery fits in the frame triangle under the seat or on the side frame — use a battery tray or heavy-duty zip ties. Fuse the positive wire (30A recommended). Wire the solenoid as follows:

• Large terminals: Battery positive to one terminal; starter positive wire to the other.
• Small terminals: One to ground (or through the start button); the other to the start switch output.

5. Wire the Start Button and Ground

The start button connects between battery positive and the solenoid’s trigger wire. When you press it, the solenoid closes and sends full battery voltage to the starter motor. Most handlebar buttons handle the 1–2 amps a solenoid coil draws, so a relay is optional. Connect the engine’s ground wire (from the stator or frame) to the battery negative terminal.

6. Connect the Charging System (if applicable)

If your engine has a lighting coil, run its output wires to a regulator/rectifier (common 4-pin units cost $10) then to the battery. Without a charging coil, you’ll need to charge the battery externally after every few rides. If you plan to ride frequently, replace the flywheel with one that has a larger magneto to boost charging capacity — check pit-bike forums for specific models.

7. Test Fire

Before final assembly, turn the key switch to “on” (if fitted) or ensure the kill switch is connected. Press the start button and watch the starter gear engagement. It should turn the engine over briskly. If it drags, check battery voltage (should be above 12.4V), the ground connection, or a seized starter. If the starter spins but doesn’t crank the engine, the gear may not be meshing — adjust the starter position or add shims.

Stop/escalate threshold: If the starter clicks but the engine doesn’t turn, first charge the battery to 12.4V+ and try again. If it still clicks, the solenoid may be faulty. If the solenoid clicks and the starter spins but still won’t engage, stop and verify gear alignment. Do not force the starter — you can strip the ring gear teeth. If you cannot get the gear to mesh after two shimming attempts, take the engine to a small-engine repair shop. That’s the point to escalate before causing permanent damage to the flywheel or transmission.

Common Issues and Fixes

When to Skip the Conversion

If your pit bike uses a rare engine (an old Italian Minarelli or a vertical-shaft engine), finding a compatible ring gear or starter bracket is difficult. In that case, swapping in a complete engine with e-start already fitted — like a Lifan 125cc — is usually cheaper and less frustrating. Also consider whether the added 2–3 pounds of battery and starter is worth it. If you only ride on a track and start the bike easily by hand, the complexity may not be justified.

If you do move forward, double-check the kit’s compatibility by measuring your flywheel diameter and crank taper. When in doubt, ask the seller for a photo of the kit installed on your exact engine model, or join a pit-bike-specific forum for guidance.

Once everything is wired and snug, you’ll never have to kick dirt out of your boot again.