Open Belt Drive Primary Assembly for Harley-Davidson

In this tutorial, we'll discuss replacing the stock closed-case oil-bath chain primary drive with an open belt drive system.
This system is widely used in racing, especially with boosted engines, due to its lightness and low inertia, quick response, and ability to transmit greater torque.
All of these benefits will be immediately available upon installation, but above all, the look of our machine will change, as we go from the smooth and boring primary cover to a wide belt spinning menacingly on the left side of our Harley-Davidson.

Let's get to work
We jump straight into action by draining the oil from the primary and removing the cover. Then, following the instructions in the service manual, we lock the primary chain and loosen the pulley and clutch nuts, allowing them to be removed.

Important: Keep in mind that the clutch nut is “left-handed” on the model we are working on, so it is tightened and loosened in the opposite way to conventional tightening.
With the primary transmission out, we can now loosen the bolts holding the internal crankcase that serves as a link between the engine and the transmission, and remove it.

Special tool
At this point, we need to remove a bushing located on the transmission shaft, which acts as an inner race for the clutch bearing located in the original cover. We need a special tool (manufactured by Baker, Jims, or Screamin' Eagle) to remove this bushing.

Mounting
We now continue with the assembly of the Belt Drive kit. The first thing we do is place the support plate on the engine and transmission and make sure it fits "naturally," that is, easily and without tension.

Once this point is checked, we can tighten the plate and the starter motor, following the kit manufacturer's instructions and using some (important) common sense. To tighten the starter motor, which we'll perform from the right side of the motorcycle, we'll use a long Allen wrench with an extension, thus avoiding having to disassemble the oil tank.
Once the plate or "interface" is in place, we can present the pulley and belt assembly. We again check that the parts fit naturally without stress.

We tighten the bolts that hold the pulley to the crankshaft and the clutch to the transmission shaft. First, we apply a couple of drops of high-strength red Loctite threadlocker and then use the torque wrench to tighten the specified torque.
We take out the clutch plates and insert them in alternating order, starting with a friction plate, then a steel plate, another friction plate, and so on until we reach the cover.

Make sure all the discs fit smoothly, without excessive friction. If there is significant friction, we can lightly file down the profile of the problematic discs.
Following the kit instructions, we install the clutch spring and perform the tightening and adjustment recommended by the manufacturer.

Spin it
At this point, we can start the engine and verify that everything is running smoothly, with no unusual noises, and that the belt runs aligned and completely parallel to the engine and transmission. Be careful not to put your fingers in the belt, and remember to wear proper eye protection.
Now we just need to install the protective covers, using a little medium-strength blue Loctite .

These covers, in addition to providing a very nice finish, prevent us from catching our foot when the engine is running, although we should never let our guard down. I know of cases where jacket sleeves, wallet chains, and trouser hems have gotten caught while driving, causing a fright.

All set
Now we can take our brand-new Belt Drive for a test ride. We'll notice that the acceleration is more direct, the bike weighs a little less, and we no longer have to worry about the primary gearbox oil level. All advantages...

Frank Burguera

#harleymechanics