YP100 Crankshaft Assy

🔧 Yamaha 100 Crankshaft Assembly

📦 Part Number: MIYP100-5013

⚙️ Replacement Crankshaft · OEM Quality · 100cc 4-Stroke

📍 Installation Position: Crankcase · Engine Center

✅ Precision Forged · Balanced · Includes Connecting Rod · Direct Replacement

This product is a Yamaha 100 Crankshaft Assembly, part number MIYP100-5013. It is a standard OEM quality replacement crankshaft assembly designed for 100cc 4-stroke engines — a core component for engine overhauls or crankshaft replacement.

The crankshaft is one of the most critical rotating components in the engine, responsible for converting the piston's reciprocating motion into rotary motion and delivering power output. With accumulated mileage, the crankshaft main journals and connecting rod journals may suffer from wear, out-of-round conditions, or scoring. The connecting rod big-end bearing may also wear, resulting in engine noise, increased vibration, power loss, or even severe failure. This crankshaft assembly is precision forged and machined, dynamically balanced, and includes the connecting rod assembly — manufactured to strict OEM quality standards for a perfect replacement that restores smooth engine operation.

• 🔩 Precision Forged: Crankshaft is forged from high-quality alloy steel for dense grain structure, high strength, and excellent fatigue resistance.
• ⚖️ Dynamically Balanced: Each crankshaft undergoes precise dynamic balancing for smooth high-speed operation and reduced engine vibration.
• 🔧 Includes Connecting Rod Assembly: Crankshaft comes complete with connecting rod assembly (including big-end bearing) — no additional parts needed.
• 🧪 Precision Machined: Journals are precision-ground with low surface roughness for accurate bearing fit and low operating noise.
• 🔄 Direct Replacement: Mounting dimensions match OEM — directly replaces the old crankshaft assembly without any modifications.

✅ Typical Signs That Crankshaft Replacement Is Needed:
• Dull knocking or metallic grinding noise during engine operation (worn crankshaft or connecting rod bearings).
• Noticeably increased engine vibration, especially at higher RPM.
• Power loss — poor acceleration.
• Visual inspection reveals significant wear, scoring, or out-of-round conditions on main or connecting rod journals.
• During engine overhaul, crankshaft replacement is recommended for complete restoration.
Replacing a damaged crankshaft promptly restores smooth engine operation and prevents further damage.

✅ Installation Tips:
1. Thoroughly clean the crankcase before removing the old crankshaft to prevent debris entry.
2. Inspect crankcase bearing bores and replace crankshaft bearings if necessary.
3. When installing the new crankshaft, pay attention to orientation — ensure timing marks are aligned.
4. When installing the piston/connecting rod assembly, confirm piston orientation.
5. Tighten crankcase bolts in OEM cross-pattern sequence in 2-3 even stages to specified torque.
6. After installation, manually rotate the crankshaft to verify smooth operation.
Crankshaft installation is a technically demanding job — professional installation by a qualified technician is strongly recommended.

⚠️ Important Notice: This product is a Yamaha 100 Crankshaft Assembly, part number MIYP100-5013. Suitable for 100cc 4-stroke GY6 series engines — OEM quality standard. Main journal diameter, crank stroke, and connecting rod length may vary across different model years or versions. We recommend confirming your original crankshaft specifications before purchase. Images are for reference only; actual product may vary.