Change of primary compensator: improving the start of Harley-Davidson

The compensator is a shock absorber

Indeed, in Harley-Davidson's Big Twin engines, the compensator acts as a shock absorber between the engine pulsations, which leave the crankshaft and are transmitted through the primary chain to the transmission, through the clutch. Therefore, a softer march is achieved and the pulls are reduced by accelerating and decelerating.

Recooking problems

Surely if you are owner (or you know someone) of a Twin Cam 96 ”, manufactured between 2007 and 2011, the typical starting problem of these models sounds: the engine rotates, but suddenly, strange noises are heard (as if something was about to break), and the pistons go back, making smoke out of the air filter.

This setback is precisely due to the fact that an old design of the primary chain compensator is being used, which worked well in the previous engines, but that is not able to manage the increase in mass of the largest modern engines, especially during the start, causing the crankshaft and the pistons to “bounce” backwards, producing the backfire that we commented previously.

The solution is already invented

To minimize this problem, we can opt for 2 solutions: a cheaper, consisting of replacing the system with a compensator eliminator, as in Sportster models, and we can also install the compensator that equips the most modern models, as of 2012.

Hands to work

We will install an update kit of the Screamin ’Eagle compensator, by Harley-Davidson.

We begin by disconnecting the battery (safety, first of all), and following the workshop manual, we drain the primary school oil and extract the lid from it. We have to thoroughly clean this lid inside to be able to paste oil deflectors.

These pieces will direct part of the circulating oil to the critical points of the compensator, to lubricate it. We will use the glue and the clip included in the kit and help each other an instrument to pressure while hardening, so that it once installed support temperatures and extreme vibrations.

We continue with the disassembly of the Internal Primary crankcase, which will allow us to extract the alternator rotor.

The rotor must be replaced because the original has including the compensator's mockery, while in the new system these are separated, facilitating the service.

Mounting

Once the new rotor is installed, we re -assemble the internal grace of the primary,

compensator gear,

The mockery and the ramp.

We ride the chain with the new crown and its nut, which wears bearings in its rear.

We perform the final tightening of the compensator and clutch using a dynamometric key and a special locking user.

We only have to install the chain tensioner, using this trick that will save us time: we compress it outside the motorcycle and hold it with a Nylon flange and, after screwing it into its location, we cut the flange to release the tension.

At this point, we set up the primary lid again and fill with 1 quart (approximately 1 liter) of specific oil for primary transmission and return to connect the battery.

Result

We can check how now the start is done in a faster and more silent way, without rebounds. And, best of all, driving in general will be softer and more progressive thanks to the improved compensator operation.

Frank Burguera

#mecanicaharley