Sputhe Engineering has been manufacturing aluminum cylinders with cast-in sleeves for Harley-Davidsons since 1977, far longer than Harley-Davidson themselves.  Our big bore cylinder assemblies for Evo Big Twins have been thoroughly tested and are manufactured from the best materials available to the most exacting standards in the industry.  Sputhe cylinders incorporate 28 unique design elements that are protected by US patent 5,072,697.


Sputhe cylinders are cast in 383 aluminum alloy, which has a tensile strength of 45,000 psi.  The aluminum is injected into a steel die at over 5,000 psi, assuring perfect bond to the Lascomite sleeve.  Lascomite is a “class 40” high tensile chrome-moly alloy having a high molecular pearlite structure.  It is centrifugally spun cast and heat treated to a hardness of 200 Brinell.  Not only is Lascomite harder than the cast iron that Harley-Davidson and other after-market cylinder manufacturers use, it is much tougher and less brittle.  The Lascomite sleeve in the Sputhe cylinder is 50% thicker than the sleeve in the stock Evo cylinder for increased rigidity.

Sputhe cylinders expand less and have better thermal dimensional stability than any iron cylinders.  The 3.780” (96 mm) bore Sputhe cylinders have a greater fin area and a symmetrical fin pattern that reduces thermal distortion and allows sustained operation at maximum power.  Sputhe cylinders are stock height so that the cylinder studs, pushrods, exhaust pipes, manifold and motor mounts do not need to be modified.  Heads and cylinders can be removed with the engine in the frame.

Part #4003S


E-Mail: sputhe@hotmail.com

Tel: (530) 268-0887
11185 Lime Kiln Road
Grass Valley, CA 95949-9715

SputheEngineering name, design and related marks are trademarks of  SputheEngineering, Inc.
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