The compensator is a shock absorber
Indeed, in Harley-Davidson Big Twin engines the compensator acts as a buffer between the engine pulsations, which leave the crankshaft and are transmitted through the primary chain to the transmission, passing through the clutch. A smoother ride is therefore achieved and jerks are reduced when accelerating and decelerating.
Surely if you own (or know someone) of a Twin Cam 96 ”, manufactured between 2007 and 2011, the typical starting problem of these models sounds familiar to you: the engine turns, but suddenly, strange noises are heard (as if something is about to break), and the pistons recoil, blowing smoke out of the air filter.
This backlash is due precisely to the fact that an older design of the primary chain balancer is being used, which worked well in previous engines, but is not able to handle the increased mass of modern larger engines, especially during the starter, causing the crankshaft and pistons to "bounce" backwards, producing the backfire we mentioned earlier.
The solution is already invented
To minimize this problem, we can opt for 2 solutions: a more economical one, consisting of replacing the system with a compensator eliminator, as in Sportster models, and we can also install the compensator that the most modern models equip, starting in 2012.
Let's do it
We are installing a Harley-Davidson Screamin ’Eagle compensator upgrade kit.
We start by disconnecting the battery (safety, above all), and following the workshop manual, drain the oil from the primary crankcase and remove the cover from it. We have to thoroughly clean this cover inside to be able to stick the oil baffles.
These parts 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 we will use an instrument to apply pressure while it hardens, so that once installed it withstands extreme temperatures and vibrations.
We continue with the disassembly of the internal crankcase of the primary, which will allow us to extract the rotor from the alternator.
The rotor must be replaced because the original includes the compensator spring discs, while in the new system these are separated, facilitating service.
Once the new rotor is installed, we reassemble the internal crankcase of the primary,
the spring discs and the ramp.
We assemble the chain with the new crown and its nut, which has bearings in its rear part.
We carry out the final tightening of the compensator and the clutch using a torque wrench and a special locking tool.
Now we only have to reinstall the chain tensioner, using this trick that will save us time: we compress it outside the motorcycle and fasten it with a nylon tie and, after screwing it in place, we cut the tie to release the tension.
At this point, we mount the primary cover again and fill with 1 quart (approximately 1 liter) of specific oil for primary transmission and reconnect the battery.
We can see how the boot is now done in a faster and quieter way, without bouncing. And best of all, the overall ride will be smoother and more progressive thanks to the improved throttle operation.