For some time I was aware of rumours about a desmodromic JAP.

In October 2001 I finally found the 1924 JAP patent.

August 23, Y2k2 I discovered a picture of the engine-block with the desmo-internals.

Source: MOTORRAD Classic; issue 5, September/October 2002 = announcement that an article will be published about this phenomenon in issue six (November/December).

Martin Slancar [http://www.classic-tech.at] is the Austrian author of the fantastic article about this interesting engine. He also made the pics and the great CadCam drawings. He actually machined the missing parts and so produced a complete power unit. Martin Slancar’s client shortly after sold the engine to a German JAP-collector, a certain Mr. Mutschler.

Werner Thum, a pratical engineer, finally did all the additional work to get this Desmo JAP-engine in a Royal Enfield motorbikeframe and everything necessary (ignition, powercurrent, carburettor adjustment, fuel supply etc.) to get the engine running. I hope to meet the owner soon to hear more about this project and to add more documents and pics to my site. The very existence of this Group 10 desmodesign is a stimulation to make the last “letter” of the desmodromic alphabeth (working model).

To be continued. Exactly 10 years later I received an article published in La Vie de la Moto nr. 729 (29-11-2012). More later….

prestwich1 prestwich0


JAP4 jap5small


[Classification = Group 10]

Patent John Alfred Prestwich

Article (in Dutch) about the making of a JAP-model. This article was published in Strada, the magazine of the Dutch Ducati Club.

2021 Strada 6 v1b – JAP

The Word.doc version translated into English: Strada Artikel JAP compleet Engelse versie