Polish JJ2S “X4” 500cc Motorcycle

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It’s easy to make Polish motorcycle jokes, and we could easily make a few more here if we were so inclined to pick-apart every little mistake a bike builder inevitably makes along the way, but we won’t. Read for more to see how the lastest version of this 4 cylinder, X-pattern motor is coming along.


having seen some of the earlier mock-ups and concept drawings for the Polish born “X4” engine bearing motorcycle, and have to say that I was immediately impressed on how this bike has been shaping up over the last year. Powered by a 500cc, 2-stroke, 4-cylinder motor, JJ2S’s X4 bike takes a new approach to a cafe racer style of motorcycle. Instead of more traditional layouts, the X4 is more analogous to a radially configured motor mounted longitudinally rather than laterally across the frame of the motorcycle. 

This configuration and mounting technique allows the bike to be very slender across the front, and allows the opposing forces of the 2-stroke motor to be fully utilized, making it an overall very efficient design. Housed inside a steel trellis frame, with projector head lights, and 6 pot front brake calipers, the bike has the look and feel of a retro-throw back cafe racer. For whatever reason, the movie Metropolis comes to mind when I look at this motorcycle. Possibly because it is just that weird, and has similar styling cues as the 1920’s (so does our global economy for that matter).

While this bike still only exists on the hard drives of a few design computer, some relative technical specifications can be discerned.

USD 43mm forks with two 320mm discs, 6-piston standard mount callipers. At the rear, a 240mm disc with 2-pistons calliper.

Front tire: 120/70 ZR17 on a 3.5″ x 17″ spoked rim.
Rear tire: 190/50 ZR17 on a 5.50″ x 17 ” spoked rim.
Seat height: 800mm
Wheelbase: 1341mm
Length: 1955mm
Width: 640mm
Height: 1138mm
Dry weight: 155kg
Fuel tank: 24l.

Source: JJS Design

Jensen Beeler

Despite his best efforts, Jensen is called one of the most influential bloggers in the motorcycle industry, and sometimes consults for motorcycle companies, whether they've solicited his expertise or not.