Hot Rods Crankshaft Assembly 4138 — Yamaha YZ250 / YZ250X 2003-2025

Product Description

Keep your legendary Yamaha 2-stroke running at its best with the Hot Rods 4138 Crankshaft Assembly. Engineered specifically for the YZ250 and YZ250X, this crankshaft is the industry standard for riders looking to restore factory-fresh performance to their bottom end without the hassle of manual assembly and truing.

Forged from high-grade 4140 steel, this crankshaft is built to handle the explosive power of 2-stroke racing. It comes pre-assembled and factory-trued to exceed OEM specifications, featuring proven Hot Rods connecting rods and top-end bearings. With precision-machined gears rated at DIN class 9 or higher, this unit is built for durability and is fully rebuildable, ensuring it remains a reliable part of your bike's engine for years to come.

Top Features: Hot Rods Crankshaft Assembly

• Sold complete with proven Hot Rods connecting rods and top-end bearings
• Factory assembled and trued to meet or exceed OEM specifications
• Heavy-duty 4140 steel construction tailored for 2-stroke performance
• Gears precision-machined to DIN class 9 quality level or higher
• Complete, pre-balanced, and ready for immediate installation

Please review the detailed compatibility data below to ensure an exact fitment match for your motorcycle before finalizing your purchase.

Fitment List

Frequently Asked Questions

Q: Is this crankshaft assembly a direct drop-in replacement?
A: Yes, it is designed as a direct OEM replacement. Because it is factory-trued, you do not need any special machining to install it in your cases.

Q: Should I use my old crankshaft seals with this assembly?
A: Absolutely not. Always install brand new crankshaft seals when replacing your crank assembly to ensure proper crankcase pressure and prevent air leaks, which can lead to a lean condition and engine failure.

Expert Pro-Tip: Since you are opening the cases, take the time to inspect the crankcase sealing surfaces for any nicks or scratches. Even a tiny imperfection can ruin your crank seals, so clean everything thoroughly with a high-quality solvent before assembly.

Recommended Pairings:
o Yamaha 2-Stroke Performance Parts
o Yamaha YZ250 / YZ250X Performance Parts
o Assembly Lube, Crank Seals, & Chemicals

At Moto-House MX, we carry the best brands in motocross and off-road performance. Our team has over 40 years of experience helping riders get more out of their bikes. Every order ships fast from our Central Florida location.

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