Twin Cam Engine Rebuild Part 5 of 5 | Hot Bike

Finishing our how to on rejuvenating a 99 Twin Cam motor

how to build a twin cam motor

Take the tappet and place it in its bore. It should slide down into the engine case effortlessly.

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The last phase of our Twin Cam A reworking takes us from the tappets to the carburetor. For you kids just now joining us at home, Hot Bike pulled the worn Twin Cam “A” motor from a 1999 FXDX out of its chassis at the 100,000 mile mark.

We broke it down, inspected it, and then sent the lower end to Darkhorse Crankworks (DHC) so its squad of bottom-end experts could rework the tired components. Working with Dave Mackie Engineering (DME), we concocted a solid 107ci top end using bored H-D cylinders and some DME Mega-Sphere pistons, complemented by a DME cam. Both DME and DHC are known for their superior quality and attention to detail, so it was a pleasure to assemble this motor knowing the end result would be a powerful yet balanced blueprinted motor.

how to build a twin cam motor

After placing both lifters in their appropriate bores, secure them with the tappet-locking bar that drops into the slot in the engine case.

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how to build a twin cam motor

Place your tappet gasket and cover over the lifter bore.

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how to build a twin cam motor

Place the four bolts into the holes to secure the covers to the case and torque to 90 to 120 inch-pounds

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how to build a twin cam motor

Now we are ready to install the intake, carb, and pushrods.

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how to build a twin cam motor

First, we install new intake seals onto our monster manifold.

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how to build a twin cam motor

We used an S&S manifold that has been hand ported to match our carb and head setup. We installed the MAP sensor prior to installing the manifold to the motor.

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how to build a twin cam motor

Install the manifold and torque the bolt in an “X” pattern so the seal can sit evenly and an intake leak does not occur.

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how to build a twin cam motor

Next, we install our custom modified Mikuni carburetor with a race back by T-Man Performance.

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how to build a twin cam motor

Install and tighten the manifold to the race back adapter on the carb.

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how to build a twin cam motor

Our motor is now ready for compression releases, pushrods, and tubes.

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how to build a twin cam motor

Screw in the compression releases and tighten to spec.

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how to build a twin cam motor

Install and adjust the front and rear pushrods, tubes, collets and covers. Install any sensors (cam, engine temp, crank position) at this time.

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how to build a twin cam motor

Pictured here is our balanced and blueprinted 107-inch thumper “A” motor. With a bottom end by DHC and a top end by DME. Good stuff, indeed!

Hot Bike Staff