Dr. Jekill & Mr. Hyde’s (J&H) novel exhaust system allows the rider to pick from three different sound modes on the fly. An illuminated, handlebar-mounted switch actuates a servo motor, which actuates a valve in the interior of the exhaust system to instantly adjust sound output to your preference.
In Dr. Jekill Mode, the valve is closed, diverting the exhaust gases around the valve and through perforations on side chambers of the exhaust, where they pass through patented single-strand fiber dampening material before being routed out. This is the quietest mode, most closely resembling the stock sound but with a much deeper tone.
A quick push of the button opens the valve halfway for Dynamic Mode, which adds a distinctive low-frequency bark. A final push of the button unleashes Mr. Hyde Mode, in which the valve opens fully and the rider is treated to the engine’s full guttural roar as exhaust gases pass through relatively unrestricted.
My BMW R 1250 GS exhaust system is governed by an ECU that plugs directly into the wiring harness, reading CANbus signals from the bike and allowing the exhaust valve to power on and off with the engine.
Installation of the J&H exhaust is straightforward. The small servo motor is mounted to the frame above the header connection, and its waterproof control wires are routed along the inside face of the muffler, where an integrated clamp holds them securely. The wiring harness is plug and play. (J&H has a helpful installation video on YouTube.)
Once installed, the J&H is a handsome pipe. Its flawlessly finished Nomad Black body leads to a glossy hexagonal carbon fiber end cap, punctuated by a gorgeous machined-aluminum accent plate on the rear. The inlet cover is finished in matching glossy carbon fiber as well. The appearance is sleek, serious, and decidedly upmarket, drawing loads of attention from fellow GS riders.
Out on the road, the BMW’s personality can be instantly transformed from mild to wild depending on my mood, and I love exercising that expression! Experienced readers are wise enough to know the difference between an annoyingly loud exhaust and an improved exhaust tone that fits with the character of each motorcycle. This J&H pipe unleashed my bikes inner growl, adding a healthy dollop of welcome character to the machine.
But in this case, it’s not about volume. Using an AudioControl DMRTA calibrated decibel meter, placing the measurement device about 20 inches from the exhaust at a 45-degree angle per the SAE J2825 standard, I measured all three modes at idle: Dr. Jekill came in at 85.9 dB, Dynamic measured 88.1 dB, and Mr. Hyde rang up 93.1 dB. For reference, SAE J2825 recommends a 92 dBA limit at idle for motorcycles.
Dr. Jekill & Mr. Hyde exhausts are the best of both worlds, allowing you to be naughty or nice without ever being obnoxious. They’re made in the Netherlands and are fully compliant with European emission laws. Testing is currently in progress for the U.S. market, and the company hopes to have CARB and EPA approval by the end of 2023.
MSRP for the BMW R 1250 GS Exhaust from Dr. Jekill and Mr. Hyde is $1,695 for black and $1,640 for silver. Each pipe is covered by a four-year, unlimited-mile warranty.