True versus untrue

Under Construction!

Some car- and motorcycle journalists and authors of books on cars and motorcycles are repeating the mistakes of yesterdays information, often without doing further research and offering the available present evidence instead.
Some just prematurely mention some car or motorcycle engine to be desmodromic.
On this site under this button I collected some of these phenomenon.
There are journalists of course who regard themselves to be just the messenger who can only report for their readers on what information they are given or shown on an exhibition or symposium and must trust the bona fides of the people interviewed and involved.


According to some sources (Encyclopedie van de auto : merken techniek modellen; Atrium, 1994 p. 32), Ariès had a 1131 V4 engine with desmodromic valve gear in the year 1907. Possibly this was a wrong interpretation of Baron Petiet’s letter published in “La Vie Automobile”, november 25, 1921. In this letter Petiet refers to a 1 cil. OHC 4 valve desmo-engine that was developed for the 1908 GP des  Voiturettes (See “Systems”).


The most “famous” example of ever continuing copying of a misinterpretation is the drawing of the supposed Mercedes desmo embodyment with “scissors-action rockers”.
This starts with the publication of an article by Alan Baker in the Motor Cycle (7 April 1955),

alanbaker3 alanbaker4 alanbaker1






repeated numerous times in articles and books and lasts till present time:,11616.html

Probably the scissor type was dreamed up in the early fifties by somebody after being informed verbally about the Mercedes forklike rockerportion and valve-rocker attachment.
When the real thing was published strange enough the old drawing was not abandonned.
Instead some thought the SLR only had the “new” embodyment and the old system was meant for the Formula 1 (= the W 196). (See picture below)

mercedesdesmowrong125 cc “Desmodromic” Mondial

It was Carlo Perelli who rectified after 45 years this long lasting misinformatio. Click:
Mondial 125
But there actually was a desmodromic Mondial (175) cc.
A new page is under construction under “systems”: Mondial 175
“Desmodromic” Ceccato

Tom Cottor : “The Vincent in the Barn : Great Stories of Motorcycle Archeology” Hardcover cop. 2009 Digital edition cop 2010
On p. 65 a chapter is titled: “Taglioni’s Desmodromic Ceccato”.
There is no text nor picture of the so-called very desmo-system in that book, but of course the Ceccato never was desmodromic.
Source: Gianni Perrone : Ceccato 75/100 In: Moto Storiche & D’epoca Anno IV n. 29 Maggio 1998 p. 43 – 53.

“Desmodromic” Cyclone Boardtrackracer”

In The Dutch Motormagazine Kickxstart (under the feature “History”) I read an article by Ivar de Gier about the Cyclone, supposed to be Desmodromic. While doing research for this article Ivar consulted some “specialists” (among whom the conservator of the A.M.A. Heritage) all claiming the Cyclone “desmo”. But when Ivar became the lucky possessor of a Cyclone himself he found out that it’s engine had conventional valve gear and that he was wrong with his desmo-statement.
Trying to convince his three information sources from yesteryear he sadly discovered a weird phenomenon. Some people are so stubborn and conservative that their immense EGO cannot confront being wrong and the adaptation of new evidence is blocked forever. One reason why these myths will preserve. Despite of rectification people tend to endlessly repeat the wrong information.

fakedesmo“Desmodromic” Honda CX 500

A collegue of my wife heard from my desmo-hobby and told her that he had a desmodromic Honda CX 500. I told my wife that this was impossible. How did he get that idea? It was printed in a book (subtitle under a factory picture). But big valve springs and only opening cams are present in this OHV system. It is not desmo at all. Weird enough I now fail to find the very page and picture, but I keep searching. Possably a Dutch source could be the reason. I have an article on valve gear with this CX500 Picture at the left page and full with desmodromics on the right page. Finally found this picture. It was published on: (now year 2001.

I decided to give up correcting the word “DesmodroNic” instead of “DesmodroMic”. Yes I know on the quertyboard the letter N is next to the letter M, but I think it is not 196.000 times (Google result on 13-11-2012) a typing error, but often ignorance instead. Even in official patenttexts the word is quite often misspelled.

“Desmodromology” might be an unexisting, non-formel scientific discipline, “Desmodrology” certainly is. I am also not going to correct this anymore. Google after this word and be surprised.

tn_028AAnother cause of spreading misinformation on desmodromic valve control is the very existence of the so called torsion bar valve systems. People misinterpret the closing rocker to be cam-controlled, but of course it is the torsion bar (= actually a spring) that forces the closing rocker and valve back into the closed position.
See also (button “Photo2”) of the non-desmo Honda CB 450 model with torsion bar.
delage1We may see the closer type rocker in some other non-desmo (spring controlled) valve gear systems, that might be confusing for the lay man as for some examiners of patent-offices as well.
One example of this first type of misinformation (drawing left) : = the Delage D6 11S (1933) with “Système de rappel des soupapes type desmodromique”.

Some examples of this kind of misinformation (wrongly classified as desmodromic = given the IPC-code F01L1/30 in patent documents):
CA2225048(Ottlyk); US3572299(Lester); US4308828(Kinsel); DE667509(Tebaldi); DE2621363(Daimler/Förster):

On the official website of Ducati: Under the button: “Company” and subbuttons “Editorial” there is the article “History of desmodromic Timing”:
In the text of this article unfortunately we can read the following famous and nearly ineradicable misinformation:
“1910 Arnott, from England, realized the first Desmodromic timing system: a “shaped annular cam” moves a rocker arm.”
In the diaseries the sentence: “First desmodromic engine built by the French Bignan” of cause is very wrong (read my article on this site).
But most amazingly wrong is mixing the Norton desmo with the Taglioni’s triple knocker.
This lasts for a long time already and I am wondering how long it will take before these mistakes will be corrected.
(NB I have done what I could and should). [Paragraph added Fall 2012].
“Desmodromic” Brushmobile
(with Vauxhall engine) mistakingly called desmodromic. Click this hyperlink for the evidence: Brushmobile

03-06-2015 (last update)