Larga noche de julio
All the sporters bikes of this page were really listed on the 24H. of Montjuic, a motorcycle endurance race, in 1974; but I have not found the entry list of that race. John Player Norton Commando
www.motorcycleclassics.com/classic-british-motorcycles/1973-John-Player-Norton-Monocoque.aspx This is not one of the John Player Norton replicas but instead the actual John Player Monocoque, of which they made three. Very, very rare.
If it helps for the ID of the sporter bikes listed, all of them are engined for a 24h. motorcycle endurance race.
BSA 500 Gold Star Mead & Tomkinson? http://www.b50.org/mead.htm
Yes, it seems the Gold Star you pointed Alessandro http://www.classicmotorcycles.org.uk/b50/b50_history.htm
It looks like this: http://www.kellymotodepoca.com/images/1973_Ducati_Sebring_350.jpg But I can't find any images of other models like this ... ducati scrambler Probably a scrambler 450, which came out of the factory in orange painting, i guess.
Couleurs spécifiques aux Ducati made in Spain?
Team Freyters ran 2 bikes in this period, a 500/4 Honda and an Egli Honda 750 (actually 810cc)
This is the Egli 750 prepared for the 1974 Bol D'or Very similar but not identical to the original 1973 picture above, will update with a definite answer soon (hopefully )