Install A Harley Twin Cam Gear Drive

Replace cam chains and gears with a gear drive.

A Harley-Davidson motorcycle owner may replace his cam chain and gears with a gear drive. This option makes the Harley a more reliable investment. The original cam chain and gears work in much the same way as the gear drive. However, slack in the chains — otherwise known as lash — leaves room for breakage and wear. The life of the gear drive is much longer than that of the chain and gear combination. The gear drive also alleviates the troublesome cam chain tensioners, which wear easily.


1. Cut the original pushrods in two with bolt cutters. They will fall out of place once you cut them.

2. Remove the outer cam cover by removing the 10 bolts holding it in place with a wrench.

3. Place the motorcycle in 4th or 5th gear and remove the spark plugs, ensuring no there is no resistance from the compression pressure. To simplify the installation of the new cams, turn the rear wheel so the timing marks on the gears align with each other.

4. Remove the outer chain tension shoe with a cam chain arm tool. Remove the retaining bolts holding the crankshaft sprocket and rear camshaft sprockets in place with a crankshaft/camshaft sprocket locking tool. Remove, with a wrench, the cam support plate and the oil pump retaining bolts that hold it in place. Because the new gear drive does not require the existing cam chain tension arms and springs, remove and discard them.

5. Press the new drive gears onto the front and rear camshafts with an arbor press. Install the camshafts into the cam support plate, ensuring alignment of the cam drive gears.

6. Check the cam gears for backlash. Hold the front cam — with a wooden rod or brass punch — to keep it from rotating while you turn the rear cam. Using a dial indicator, note the amount of backlash. Recommended backlash is between 0.0005 and 0.001.

7. Install the rear cam drive and the crankshaft drive gear. Secure them in place with the retaining cap screws. Tighten them to 25 foot-pounds with a torque wrench.

8. Check the crankshaft and rear cam drive gears for backlash. Using a dial indicator, note the backlash. Recommended backlash is between 0.0005 and 0.001. Rotate the gears 90 degrees and recheck the backlash. Repeat until you have checked the backlash at four positions.

9. Reinstall the outer cam cover and the 10 cover bolts holding it in place. Tighten the bolts to 90 to 120 inch-pounds with a torque wrench.

10. Install new adjustable pushrods. Install the two longer exhaust pushrods plus the two shorter intake pushrods into their respective positions in the valve train.