Primary Compensator Replacement: Improving Harley-Davidson Start-Up

The compensator is a shock absorber

Indeed, in Harley-Davidson Big Twin engines, the balancer acts as a buffer between engine pulsations, which emanate from the crankshaft and are transmitted through the primary chain to the transmission, passing through the clutch. This results in a smoother ride and reduces jerks during acceleration and deceleration.

Backlash problems

Surely if you are the owner (or know someone) of a Twin Cam 96”, manufactured between 2007 and 2011, you are familiar with the typical starting problem of these models: the engine turns, but suddenly, you hear strange noises (as if something were about to break), and the pistons move back, causing smoke to come out of the air filter.

This recoil is due precisely to the use of an old design of the primary chain compensator, which worked well in previous engines, but is unable to handle the increased mass of larger modern engines, especially during start-up, causing the crankshaft and pistons to "bounce" backward, producing the backfire we mentioned earlier.

The solution has already been invented

To minimize this problem, we can opt for two solutions: a more economical one, consisting of replacing the system with a compensator eliminator, as in the Sportster models, or we can also install the compensator equipped on more modern models, from 2012 onwards.

Let's get to work

We're going to be installing a Harley-Davidson Screamin' Eagle balancer upgrade kit.

We start by disconnecting the battery (safety first), and following the workshop manual, we drain the oil from the primary oil pan and remove the oil cover. We must thoroughly clean the inside of this cover to be able to attach the oil deflectors.

These parts will direct some of the circulating oil to the compensator's critical points to lubricate it. We'll use the glue and clip included in the kit and use a tool to apply pressure while it hardens, ensuring it can withstand extreme temperatures and vibrations once installed.

We continue with the disassembly of the internal primary casing, which will allow us to remove the alternator rotor.

The rotor must be replaced because the original includes the compensator spring discs, while in the new system these are separate, making servicing easier.

Mounting

Once the new rotor is installed, we reassemble the internal primary casing,

the compensator gear,

the spring discs and the ramp.

We assemble the chain with the new sprocket and its nut, which has bearings at the rear.

We perform the final tightening of the compensator and clutch using a torque wrench and a special locking tool.

Now all that's left is to reinstall the chain tensioner, using this time-saving trick: compress it outside the bike and secure it with a nylon cable tie. After screwing it into place, cut the cable tie to release the tension.

At this point, we remount the primary cover and fill it with 1 quart (approximately 1 liter) of specific oil for primary transmission and reconnect the battery.

Result

We'll notice how the starting process is now faster and quieter, without any bouncing. And, best of all, the overall ride will be smoother and more progressive thanks to the improved balancer function.

Frank Burguera

#harleymechanics