Triumph Hex Head Crankcase Bolt 5/16-inch-18 x 1-7/8-inch PN# 21-1870 S1870

Restore your classic Triumph motorcycle with this authentic 5/16″-18 x 1 7/8″ hex head bolt, designed to meet original factory specifications for a secure and reliable engine assembly. Key Features: Diameter: 5/16 inch Thread Pitch: 18 Threads Per Inch (TPI), UNC (Unified National Coarse) Length: 1-7/8 inches Part Number: 21-1870 (also referenced as S1870 or 211870) Head Style: Hex head Material: High-quality steel, available zinc-plated or plain depending on supplier Applications: Specifically used as a rear crankcase bolt on Triumph 650 and 750 models, including T120, TR6, T140, and TR7 Fits late 1960s and 1970s Triumph unit-construction engines Essential for securing crankcase halves and other critical engine components Benefits: Manufactured to original Triumph specifications for precise fit and durability Ideal for restoration, engine rebuilds, or routine maintenance Helps ensure structural integrity and long-term reliability of your engine assembly Material Steel (zinc-plated/plain) Application Rear crankcase, engine Cross-References: Also listed as S1870 and 211870 in some catalogs Sometimes misprinted as 51870 in older manuals Related bolts: 21-1869 (for similar applications with different length) Note: Always verify compatibility with your specific Triumph model and consult your parts manual for correct installation and torque specifications. Using the correct hardware is crucial for maintaining engine safety and performance. The product images shown are for illustrative purposes only and may not be an exact representation of the product received. Manufacturers occasionally make minor cosmetic changes to items, such as color, finish, label, or design. These changes do not impact the item’s function or compatibility. Please contact us if you have specific concerns regarding appearance.