C100 Initiative Gear

C100 Primary Drive Gear

⚙️ Drive Gear · Primary Drive Gear · Crankshaft Gear

For Moped, Cub & ATV · Fits 139FMB, 147FMD, 147FMF, 150FMG engines

This is the C100 Primary Drive Gear (also known as primary drive gear or crankshaft gear), a critical component of the engine's primary drive system. It is suitable for Mopeds, Cub series, and ATVs, and fits engines including 139FMB, 147FMD, 147FMF, 150FMG, and similar models.

The primary drive gear is mounted on the crankshaft and meshes with the clutch driven gear, transmitting power from the crankshaft to the clutch assembly, which then transfers power to the transmission. Manufactured from high-quality alloy steel with precision-machined teeth and heat treatment, it offers excellent wear resistance, impact strength, and transmission accuracy. This gear is the ideal replacement when the original shows signs of wear, broken teeth, or abnormal noise.

This primary drive gear fits the following engine models:

• Mopeds - Various 50cc-150cc moped models (underbones, scooters, etc.)
• Cub Series - Honda Cub and clone models
• ATVs - Small-engine quad bikes / kids ATVs
• Dirt Bikes - Small off-road motorcycles
• Other vehicles using 139FMB, 147FMD, 147FMF, 150FMG engines

• Transmission Noise: Rhythmic gear engagement noise or knocking from the clutch side that changes with engine RPM.
• Jerky Takeoff: Noticeable vibration or jerking when starting from a stop, indicating uneven power transmission.
• Power Loss: Reduced power transfer efficiency, especially noticeable during hard acceleration.
• Worn or Broken Teeth: Inspection reveals severe wear, pitting, or chipped/broken teeth on the gear.
• Clutch Slipping Sensation: Severe gear wear may create a sensation similar to clutch slippage.
• Metal Particles: Metal powder or debris found in transmission oil during draining.

If you experience these symptoms, inspect the primary drive gear and matching driven gear, and replace if necessary.

• OEM Specifications: Manufactured to original tooth profile, count, and dimensions for perfect meshing with the driven gear.
• High-Quality Alloy Steel: Made from high-strength alloy steel with excellent toughness and fatigue resistance.
• Precision-Machined Teeth: Precision hobbing and grinding ensure smooth engagement and high transmission efficiency.
• Carburizing & Hardening: Professional heat treatment provides high surface hardness and superior wear resistance for long service life.
• Direct Replacement: Directly replaces worn or damaged original primary drive gear without modification.

🔧 Installation Tip

1. Replacing the primary drive gear requires removing the engine right side cover and clutch assembly; professional installation is recommended.
2. Thoroughly clean the crankshaft end and gear mounting surface to remove oil and debris before installation.
3. It is recommended to inspect and replace the matching driven gear simultaneously to ensure proper gear meshing.
4. Pay attention to gear orientation during installation and ensure proper positioning on the crankshaft.
5. Tighten the gear retaining nut or bolt to the specified torque.
6. After installation, manually rotate the crankshaft to check for smooth gear engagement without binding.
7. Fill with appropriate transmission oil, start the engine, and check for abnormal noise to confirm proper operation.

⚠️ Important Notice: This is a C100 primary drive gear suitable for Mopeds, Cubs, ATVs, and vehicles using 139FMB, 147FMD, 147FMF, 150FMG engines.
Size Selection: Different displacement engines use different drive gear tooth counts. For 70cc/90cc engines, select 14T-15T specification. For 110cc/125cc engines, select 16T-17T specification. Please verify your engine displacement and original gear tooth count before purchase. It is recommended to replace the matching driven gear simultaneously for optimal meshing condition.
Installation Notes: Pay attention to gear orientation and tighten to the specified torque. Images are for reference only. The actual product may vary.