We tested the KessTech exhausts approved for Harley-Davidson.

It's a fact. One of the first things users modify on any motorcycle (especially custom models) is the exhaust system.
Due to current regulations, sound emissions are regulated, which is what forces manufacturers to use increasingly voluminous and restrictive exhausts, which for practical purposes and in most cases makes our motorcycles sound more like a household appliance than an internal combustion engine. The worst part is that such a closed exhaust affects the power that the engine is capable of delivering, reducing its efficiency.
The truth is that deciding how much noise we can make or not, without disturbing anyone but allowing our machine to function optimally, while also complying with regulations, is a very complicated balance.

Options
Many exhaust brands are offering "legal" products and new features as alternatives to stock exhausts, seeking to improve the look, sound, and performance. Although major American manufacturers are already beginning to offer their products adapted to European regulations (they have to sell), the reality is that European companies are significantly ahead in this regard. Manufacturers such as Austrian BSL, Slovenian Akrapovic, and German KessTech offer a wide range of exhaust options that meet the standard, sound better, and deliver more power.

The KessTech solution
We're specifically going to talk about the latest variable exhaust sound system from the guys at KessTech. The design team has done a great job, delivering a deep, powerful sound and boosting performance by up to 15 hp by reinventing the old sliding valve system (which, incidentally, Harley-Davidson has been incorporating on Big Twin models since 2007 to homologate its bikes in Europe under the name "active exhaust").
The system basically consists of an opening valve actuated by an electric motor through a small connecting shaft.

The truly interesting thing about this configuration is that it has been equipped with software that allows the system to be left operating at all times while remaining legal. This is achieved by applying regulations and closing the valve based on engine speed and RPM. Roughly summarized: the valve remains fully open (with maximum noise) at idle, 1st, 4th, 5th, and 6th gears, and closes in 2nd and 3rd. Of course, the system also allows us to always drive with the valve closed or always with the valve open (only on non-public roads ;-).

Facility
We will mount our kit on a Harley-Davidson Road King Screamin' Eagle.

Despite the technical complexity involved, installation is truly simple. To do this, simply remove the original exhaust pipes (as always, consult your model's workshop manual) and slide in the new exhausts.
Next we will tighten the rear fastening screws

And then we'll tighten the exhaust clamps. For optimal sealing, we must ensure the clamps are in their correct position before tightening.

The next step is to run the connecting cable from each of the exhaust valve motors to the area under the seat,

where we will carry out the corresponding welds following the assembly instructions.

We need to install the system start button in an accessible area of the handlebar.

and now we can finish with the connections and reassemble the seat.

Checking and adjusting
Before starting the motorcycle for the first time, we will ensure that the valve opens and closes completely when the button is pressed.

If it's working correctly, we can hit the road to check the sound, and we'll take the opportunity to record data and create a new injection and ignition map. Remember, we've modified the amount of air coming out of the engine, and we need to update the information by reprogramming the ECM.

Finally, you can hear the difference in sound with the exhaust valve open or closed in the following video:

Frank Burguera

#harleymechanics