Gy6 172Cc Stage 2 Engine Kit – Fuel-Injected

Description

Here are links to each individual part 👇

• 172cc Cast Piston Cylinder – Rolling Wrench
• 172cc Forged Piston Cylinder – ProBld
• GY6 61mm Performance Big Valve Head
• GY6 Performance Camshaft – ProBld
• NCY Performance Cylinder
• NCY Performance Cylinder Head
• GY6 Camshaft – NCY
• Shorty Pro Clocking Flange
• GY6 Scooter Spark Plug (Pre-gapped)
• 8mm Exhaust Studs + Nuts
• ProBld GY6 Full Auto Tune EFI System

Prefer a PWK carb version instead? 👉 Click here!
Want to upgrade to stage 3? 👉  Click here!

Stage 2 EFI takes our proven 172cc big-bore setup and replaces the carb completely with a full auto-tune fuel injection system. No jetting, no elevation guesswork, no cold-start stumble — the ECU constantly adjusts fueling so you just key on and ride.

• 🔥 Full 172cc big-bore + EFI combo
• 🤖 Auto-tune fueling (no jets to swap)
• 💨 Stronger pull + cleaner throttle everywhere

The Details ⚙️

This kit builds on the same cool-running 172cc Stage 1 foundation — the largest displacement you can run without case boring — and adds a self-correcting EFI system on top.

EFI System Includes:

• Throttle body with integrated ECU + injector
• O₂ sensor + weld-in bung
• Atmospheric pressure + throttle position sensors
• High-pressure fuel pump (~42 psi)
• EFI wiring harness (simple 3-wire connection)
• UNI pod air filter (pre-installed)

Charging / Magneto Options:

• 11-pole magneto — perfect for most riders
• 18-pole magneto — higher output for builds with big electrical load

Top-End Package Choices:

Full ProBld (Forged) — strongest + coolest running:

• 4032 forged piston
• Rings pre-measured and installed
• ProBld big-valve head (28 mm / 23 mm)
• ProBld performance camshaft
• 5-axis CNC clocking flange
• NGK spark plug + all needed hardware

Full Rolling Wrench (Cast) — value-minded daily setup, rings installed:

• Cast piston
• Rings pre-measured and installed
• ProBld big-valve head (28 mm / 23 mm)
• ProBld camshaft tuned for torque
• Clocking flange + NGK spark plug included

Full NCY (Cast) — value-minded daily setup:

• Cast piston
• Rings installed by you
• NCY big-valve head (28 mm / 23 mm)
• NCY camshaft tuned for torque
• Clocking flange + NGK spark plug included

Already running Stage 1? This is the plug-and-play upgrade that unlocks the full potential of your build.

What’s Included 📦

• Complete 172cc top-end package (ProBld or NCY — your choice)
• EFI throttle body with ECU + injector
• O₂ sensor + bung
• High-pressure fuel pump setup
• EFI wiring harness
• UNI pod filter
• Magneto/charging option (per your selection)
• All required hardware and fittings

Fitment 🔍

• QMJ157 GY6 engines only (no QMB / QMI)
• Honda Ruckus GY6 swap builds
• Maddog / stretched GY6 scooters
• Most 150–232cc GY6 scoots + buggies using QMJ157

Engine code is stamped near the center stand pivot — confirm QMJ157 before ordering.

Important Things to Note 🚨

• Verify QMJ157 engine code before purchasing. (How to check)
• EFI requires a fuel return — drill-in nipple included or use EFI Crown Gas Cap.
• High-accessory builds should choose the 18-pole magneto for more power output.

Need help choosing ProBld vs NCY or configuring the EFI? We’re here to help 👍

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