From the USSR: Riga 50cc racers.
The Latvian Sarkana Zvaigzne (Red Star) moped factory made mopeds under the brand name “Riga” named after the city they were made in. But they also made a lot of 50cc racebikes ,a fact not so widely known in the west. They are one of the few factories who made 50cc racebikes in series. It is very hard to get info about Riga bikes. The old east-west barrier still has its effects. Also the Riga bikes were not for export to the west in any way. The one that made it to the west before the wall came down was stripped of its internals (state secrets inside) Not that there was anything to learn from the engine internals… The engine was made not by Riga ,but by the Serpuchov scientific institute near Moscow. Soviet system made a sharp difference between production facilities and engineering- and design facilities. The Serpuchov one was for automotive research. All soviet motorsport designs that are not based on normal production parts (like the Vostok 4 cilinder racebike) come from this institute. The ShK 50 engine mounted in the most successful Riga models was a well designed engine. It has a 6 speed gearbox of cassette type ,a dry clutch and a rotary disc valve inlet. Technically the gearbox has some MZ influences ,and the cylinder and crankshaft parts have some similarities with early Jamathi racebikes. This is no coincidence ,as the Jamathi team earned a little money by helping the Riga team with some tuning ideas and by selling them the needed racing quality parts for the Riga team bikes. Meeting point were the GP at Sachsenring and Brno.
The Riga racing department was the product of a few enthousiast people. Chief was Valdis Kleinbergs and the engineers were his sister Rüta Kleinberga ,who later married rider Alexandrs Smertjevs ,and thus became Rüta Smertjeva. Other important team members were rider Eduard.Borissenko and engineer Valdis Pogainis. Except fort the engine ,the whole bike was made at the Riga factory. A name that needs to be named is the designer of the bodywork Gunars Gludins ,who created the clean and floating lines of the most successful Riga racers. The man now is a professor at the Latvian art school.
First Riga racebike was the SZ50 ,made in 1964. This racebike had a Vairas engine ,like the Riga moped ,but this one had 5 speeds. In 1966 came the 6s ,the first to have 2 important ingredients of the most successful Riga racers : a Sepuchov engine ,and a central tube frame (mostly called EGLI frame ,but please note the year of building of this Riga bike compared to that of the EGLI racers)
Via 7S, 9S ,11S we come to 15S (13S skipped,unlucky) This is the most successful Riga racebike. It was this bike that competed in some GP races. It was also the bike that was made in the biggest numbers: 32 pieces from 1972 to 1976. Two of these were the GP racers ,they had some special features like pressure oil feed to the crankshaft. The other were production racers made for the Soviet motoclubs. After the still aircooled 15S came the watercooled versions of it named 17S ,19S and the casted magnesium wheeled 21S. The 21S was the last of the 50cc Rigas ,made in 1983 as experiment.
Total production of all Riga racebikes will be around 70 pieces. After the wall came down and Latvia became independent the loss of traditional export markets and engine suppliers as well as the lack of building quality (had not always been a problem ,Riga produced some well made mopeds in the 70’s) caused the Riga factory to close.