Full Service Crankcase

Exceeding Harley-Davidson Specifications

Darkhorse Motor Company is the "go to" facility for the high performance engine builders and Harley-Davidson dealer network in ALL H-D crankcase repair, upgrades, blueprinting and assembly.  Our primary goal is to engineer crankcase upgrades to combat the motor company cost reduction directives.

At Darkhorse Motor Company, we blueprint all crankcase and crankshaft work to meet or exceed Harley-Davidson specifications. We take every major build back to the basics of a blueprint, verifying case bore alignments and crankshaft run-outs. Our directive from day one in the engine assembly shop, has been paying attention to details. Coupled with our master machinist capabilities, engineers, and cranksmiths, there are no shortcuts taken in blueprinting and assembling the foundation to many of the highest output Harley-Davidson engines throughout the world!


Keeping with our commitment to precision is highlighted by our capabilities with state of the art machining & tooling.  We manufacture all of our proprietary products and crankcase upgrades in house in our American made HAAS CNC machines.  


All work must be accompanied with a Remanufacture Work Order formWork order forms may be filled out online or downloaded from this website and copied for EACH job order. No dealer discounts are given without Dealer application being approved and on file upon completion of work. Our procedures do not include parts cost. We work on brand new to very old crankshafts and cases. It is impossible for us to have set flat rates for our procedures. Please contact us if you need a quote or have any questions by contacting  Andrew in our Technical Sales Team at (920) 726-9999, or by clicking on the button below and filling out our contact form.

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Our crankshafts will install as any stock flywheel per the manufacturer's recommendations. We hold strict tolerances according to or exceeding manufacturer's recommendations and ask that you do the same.  We will blueprint your entire lower end and assemble it for you, just ask our technical sales rep for details!

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Our Roots are Deep

Don't let our world renowned work on TwinCams and Milwaukee 8's fool you, our roots are deep in Evo's, Shovels, Pans, Knuckles and ALL Sportsters! When we line bore cases, we ask you to utilize your pinion shaft bearing race and we will supply pinion bearing that must be used for proper fitment. Your pinion shaft bearing race MUST be used for proper fitment. We will not be responsible for improper fitment if our machinists are unable to measure your pinion race. When pinion races do not meet our specs, have the pinion replacement serviced and tolerance checked and proper bearings fitted.

We give you a straight forward solution to long term reliability in a no-nonsense approach to solving foundational issues in lower end engine failures.

Crankcase Repair, Upgrades, Blueprinting & Assembly Info

TC & M8 Timken Bearing Upgrades

Shortly after the double flat-roller bearing motors were released in 2003, we started getting requests from performance shops to design a system that would support the ever growing displacement and horsepower outputs from the new engine design.   

Our unique Timken® Bearing upgrade system for Harley Davidson Milwaukee 8® & TwinCam® models is a cut above the competitions with our procedure to retain the rightside bearing along verifying main bearing bore alignment of < .001" in our CNC mills

If there are any questions or concerns regarding one of our Timken® bearing conversion cases in late model Twin Cam applications, please refer to Harley Davidson ®1999' or 2000' FLT Service and parts manual for FLHT, FLT and FLHR models, 99' or 00' Dyna Service and parts manual for any Dyna series and 2000' Service or parts manual only for Softail series bikes. We install races and pre-set Timken® bearing end-play between .002” - .0025" You must check this measurement upon final installation into case and make sure they are within factory specs of .001” - .005”. This is very critical to the longevity of your motor and related parts. Darkhorse Motor Company will supply the corresponding correct sprocket shaft spacer, unless notified at time of shipping. DO NOT interchange INA® bearing sprocket shaft spacers for Timken® style bearing spacer. This will cause damage to primary components and may cause injury or death.

Cam Bearing Repairs

With the sheer numbers of higher mileage motors in today’s market, we developed processes to repair cam bearing, upgrade early TC cam bearings to late model cam bearings, repair cam follower (lifter) bores and main bearing bores along with the true solution to cam support plate bushing fitment or replacement.

At Darkhorse Motor Company, we focus on cases and cranks so you don't have to.  Let us take care of the foundation to your build so you can concentrate on all the upper end details.  If your looking for a trusted source for top-end work, we invite you to search our dealer network in your area. These professionals are your local source for our product and much more!

Always refer to a factory service manual if in doubt on assembly procedures. 

Case Boring

We bore cases according to cylinder manufacturers tolerances. These vary and we have specific processes for each manufacturer. We may choose to position center case bolt as a through bolt versus a tapped blind hole for added structural integrity.  You may receive top center case bolt with cases that must be used which is integrated to that specific bore and case. The positioning of this bolt is critical and must align with case opening so it does not distort cylinders upon installation. Weeping at center case bolt may occur if not sealed properly. We recommend a semi-drying liquid gasket and a clean surface behind the sealing washers of case bolt supplied to deter any weeping from occurring on either side.