The 125cc 150cc Technical Bible Library 

 Yamaha MT125 / MT15 (Engine Code: E3A2E / E31FE)

Essential factory figures for the single-cylinder SOHC 4-valve liquid-cooled engine featuring Variable Valve Actuation (VVA).

🔧 Valve Clearances (Cold Engine)

• Intake Clearance: 0.10 mm to 0.14 mm

• Exhaust Clearance: 0.20 mm to 0.24 mm

🔩 Critical Fastener Torque Settings

• Cylinder Head Nuts (M8): 22 Nm (Follow cross-pattern sequence)

• Spark Plug: 13 Nm

• Engine Oil Drain Bolt: 32 Nm

• Oil Filter Cover Bolts: 10 Nm

• Front Axle Nut: 59 Nm

• Rear Axle Nut: 85 Nm

💧 Fluid Capacities & Settings

• Engine Oil Change (Periodic): 0.95 Liters

• Engine Oil Change (With Filter Removal): 1.00 Liter

• Recommended Weight: SAE 10W-40 (API SG or higher, JASO MA)

• Idle Speed: 1,300 to 1,500 RPM

 Aprilia RS125 (Rotax 122 Engine)

High-performance specifications for the legendary single-cylinder 2-stroke liquid-cooled crankcase reed-valve motor.

📐 Cylinder & Piston Tolerances

• Standard Cylinder Bore: 54.000 mm to 54.015 mm

• Piston-to-Cylinder Clearance: 0.035 mm to 0.045 mm

• Piston Ring End Gap: 0.15 mm to 0.30 mm

🔩 Critical Fastener Torque Settings

• Cylinder Head Nuts (M8): 27 Nm to 30 Nm (Tighten progressively in stages)

• Cylinder Base Nuts: 30 Nm

• Crankcase Assembly Screws (M6): 10 Nm

• Clutch Hub Nut: 90 Nm (Use thread locker)

• Flywheel / Magneto Nut: 90 Nm

💧 Fluid Capacities & Dimensions

• Gearbox Oil Capacity: 600 ml

• Gearbox Oil Type: SAE 75W-90 or 80W-90 (JASO MA rated)

• Squish Clearance (Minimum): 1.20 mm

• Spark Plug Gap (NGK BR10EG): 0.6 mm to 0.7 mm

Yamaha YBR 125 (Engine Code: 3D9)

Bulletproof parameters for the air-cooled, 2-valve, 4-stroke SOHC commuter engine.

🔧 Valve Clearances (Cold Engine)

• Intake Clearance: 0.08 mm to 0.12 mm

• Exhaust Clearance: 0.10 mm to 0.14 mm

🔩 Critical Fastener Torque Settings

• Cylinder Head Cap Nuts: 22 Nm

• Cylinder Head Side Bolt (M6): 10 Nm

• Spark Plug (NGK CR6HSA): 12.5 Nm

• Engine Oil Drain Plug: 20 Nm

• Flywheel Rotor Nut: 70 Nm

💧 Fluid Capacities

• Total Engine Oil Volume: 1.20 Liters

• Periodic Oil Change Volume: 1.00 Liter

• Recommended Grade: SAE 10W-40 or 20W-50 (JASO MA)

Cagiva Mito 125 (6-Speed & 7-Speed variants)

Factory dimensions and configurations for the high-revving 2-stroke engine featuring the CTS (Cagiva Torque System) electronic power valve.

📐 Mechanical Clearances & Timing

• Standard Cylinder Bore: 56.000 mm

• Piston-to-Wall Clearance (Standard): 0.055 mm to 0.065 mm

• Ignition Timing (Fixed): 1.5 mm Before Top Dead Center (BTDC)

• Squish Clearance: 1.25 mm to 1.35 mm

🔩 Critical Fastener Torque Settings

• Cylinder Head Nuts: 25 Nm

• Cylinder Base Holding Nuts: 30 Nm

• Crankcase Halves Screws: 10 Nm

• Clutch Pressure Plate Bolts: 6 Nm

💧 Capacities

• Gearbox Lubricant Volume: 800 ml (SAE 10W-40 or 80W Gear Oil)

• Cooling System Capacity: 1.20 Liters

Yamaha Aerox 125 / 155 (Blue Core / VVA Platform)

Liquid-cooled automatic CVT scooter engine specifications.

🔧 Valvetrain & Top End Specs

• Intake Valve Clearance (Cold): 0.10 mm to 0.14 mm

• Exhaust Valve Clearance (Cold): 0.21 mm to 0.25 mm

• Spark Plug Gap (NGK CPR8EA-9): 0.8 mm to 0.9 mm

🔩 Critical Fastener Torque Settings

• Cylinder Head Nuts: 22 Nm

• Variator Nut (Front CVT Pulley): 49 Nm

• Clutch Bell Nut (Rear CVT Pulley): 49 Nm

• Engine Oil Drain Plug: 20 Nm

💧 Fluid Capacities

• Engine Oil Periodic Capacity: 0.90 Liters

• Final Transmission Gear Oil Change: 120 ml (SAE 10W-40 Motor Oil or 80W Scooter Gear Oil)

Do you cover other 125cc models?

 "We are constantly expanding our library. If you don't see your bike here, [Join our Mailing List/Contact Us] to be notified when the next Bible drops."

Is this a physical book or a PDF?

 "These are high-quality digital guides (Kindle/E-book) designed for instant access on your phone, tablet, or PC while you work."

Are these official factory manuals? 

Our Bibles are independent, high-quality technical guides. We consolidate factory-spec data, torque settings, and service intervals into a format that is much easier to read and follow than a standard 500-page workshop manual. We focus on what the DIY owner actually needs to know.

Can I access the guide offline in my garage? 

Yes. Once you download the guide via the Kindle app or your e-book reader, it is stored locally on your device. You don't need a Wi-Fi connection to check your torque settings or wiring diagrams while you’re working on the bike.

 I’m not a professional mechanic. Is this guide too advanced for me? 

Not at all. We’ve stripped away the complex "factory-speak" and replaced it with clear, actionable instructions. Whether you are changing your first spark plug or doing a full coolant flush, our guides walk you through the process step-by-step.