Sputhe began his association with R & S Pattern Co.: A company specializing in the design and manufacture of patterns, permanent molds and investment dies.  A reputation for quality and innovation led to contracts with NASA to build wind tunnel models for the Space Shuttle; food and pharmaceutical processing equipment; medical and dental instruments.  This diversification led to the formation of Sputhe Engineering, a company that integrated engineering with the manufacturing process.



Developed the “mini-sump” for the XR-750 (Harley-Davidson has adopted this feature on every model engine that they build).



Alan Sputhe designed and built a set of dual carburetor aluminum heads for the 1000cc street Sportster that he raced at El Mirage Dry Lake in Southern California.  This machine was timed at 157 m.p.h.



Alan designed and built his first cast aluminum big bore cylinders and redesigned the heads to suit.  The performance of this engine caught the attention of the Harley racers who demanded replicas.


Sputhe Engineering began building complete Sportster based 1300cc aluminum XR-750 type engines.



Sputhe powered machines won the AFM Open GP, and Open Super Street Championship and set a record at Bonneville; 1300 MPS-AG at 176 MP (this record still unofficially stands as the 1350 P MPS G record 24 years later), won numerous hill climbs and set many drag strip records.  Cycle World Magazine road tested a street version and declared it to be the “fastest motorcycle of any kind that this magazine has ever tested” (July, 1980).  To this day it is still the fastest Harley-Davidson.



A Sputhe powered machine again won the AFM Open Superstreet and Open GP Championships.  Established a new Bonneville record in 1300 APG-AG.  Alan Sputhe won first place for the 1981 season in S.C.T.A. Dry Lakes Championship.  Moved from Southern California to our present Grass Valley location.


Introduced offset cam chest, high deck, Sportster crankcases
1983 Built the first of the famous 5-speed automatic Sportsters.
 1984  Introduced the 5-speed transmission case for 4-speed frames.  Built the first 4-valve heads for Harley-Davidson Big Twins. 


Acquired Froyd’s Grinding Service, which greatly expanded our production capabilities.


Introduced the 95” and 104” aluminum EVO cylinder kits.  Acquired the Nitralloy Co.  Moved into our present building.
1990 Became totally CNC.  All machine work is now done in-house.  Introduced an improved die-cast version of the Nitralloy ™ cylinders.

The first Sputhe 60-degree installed in a road bike (112 cid. in a FLHT chassis).  60-degree engine banned from US drag racing.


Began production of Big Twin crankcases, high performance EVO cylinder heads, The Sputhe 60-degree engine, and dual carb induction systems.  Australian Danny Grotto sets records on 120 cid. 60-degree Sputhe powered dragster.


Began production of complete 5-speed transmissions for 4-speed frames, high deck 4-inch bore racing and street crankcases.  The first 125” Evo engines.


Began producing high performance Sputhe FXR type motorcycles custom built to the customer’s specifications.


The Sputhe Spectre set an unofficial Bonneville record of 158 m.p.h. (poor salt condition canceled formal record attempts that year) and won the White Brothers Horsepower shootout with 125 hp at the Long Beach Mukuni Show.


Began limited series production of the Spectre motorcycle powered by the Sputhe 60-degree engine.


Introduced right side drive transmissions.  Introduced the Fatvo crankcase.  Introduced a super narrow version of the kick-starter five speeds for four speed frames.  Introduced lightweight aluminum swing arms for FXR, FXD, FXST, - XL and Buell.


Introduced super heavy-duty gear clusters for drag racing and big inch street bikes.  Introduced a totally redesigned 4 to 5 speed case and bearing housing that is twice as strong as any other case made.  Introduced belt drive primaries for Softails.

2004 Introduced the automatic neutral finder and a wide tire kit for Dynas.
2005 Primary Belt Drive earned Easyrider’s award for Performance Product 2005.

Mike Lodsdens Areal Rectangular 8 1987

Mike Logsdens Sputhe Sportster Bonneville 1979

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.
SputheEngineering, Inc. ©1997-2013.  All Rights Reserved.