The legend of Soviet sports - the M-75 racing motorcycle and its modifications

Remembering the Soviet motorcycles, few people think about their sports career. Well, can these low-power two-wheeled machines be connected with any achievements?


But if you strain your memory, won't really sporty models of Soviet motorcycles come to mind? For example, Izh Planet Sport? And how many cross-country bikes from the Minsk and Izhevsk motorcycle plants were there?

They also made sports motorcycles in Irbit, and at one time they were considered the most powerful and fastest in the USSR. And domestic riders even won them in international competitions! Today we will tell you about the most eminent Soviet sports bike - M-75M.

pre-war history

The first specialized models for competitions in the USSR appeared in the early 1930s. They were assembled by enthusiasts, then the racers finalized the production models, focusing on their needs.



One of the first sports piece bikes began to be produced at the Taganrog Stalin Tool Plant. These models were called TIZ. In Leningrad, they made their own bike - S-1, and in Izhevsk they assembled several samples based on Izh-7 and 8.



But the M-72, created on the basis of the German BMW R71 model, was considered the best bike in the USSR. In the late 1930s, the Soviet Union barely acquired a few motorcycles from Germany through a front company in Switzerland. I had to create my copy without documentation - the Germans flatly refused to cooperate and transfer their developments.

The main purpose of the M-72 is its use as military equipment.

Development of a new engine

Until November 1941, the Moscow motorcycle plant made heavy models with a sidecar for the Red Army. Then the production was evacuated to Irbit, where production resumed in February 1942.



Despite the difficult military situation, the motorcycle plant worked on the creation of a new, more advanced engine. It was ready in 1943.

The main changes in the new motor:

• ? Cylinders and valves from the BMW R75
  
• ? Power increase up to 28 liters. With.
  

By the way, archival documents indicate that the donor for the new engine was the BMW R-51 model. But it's most likely just a typo.

Creating a new engine, the designers did not think about any sporting achievements there. Their task was to introduce a more powerful engine for a military motorcycle.

In 1945, an experimental civilian M-75 was manufactured in Irbit. The model did not go into the series, but the work continued, already directed towards the sports direction.



Around the same time, the M-80 model was created.

Features M-75

The early sports M-75s, except for the engine, did not differ from the serial M-72s externally and technically.

Features of the model:

• ? Overhead valve cylinder heads
  
• ? Power 35 l. With.
  
• ? New aluminum carburetors
  
• ? Lack of air filter and lights
  
• ? Other lubrication and ignition systems
  

Some motorcycles were modified by riders on their own. As a result of minor changes in the design, for example, gear ratios in the gearbox, it was possible to increase the power to 44 hp. With.

The bike was made to be as light as possible. Mud wings were not abandoned, but they were made narrower. The trunk was not installed. Some riders even removed the kickstarter to make the bike easier to build.



In Serpukhov, the All-Russian Research Institute was finalizing the serial M-75, focusing on the feedback from the riders and the results of the competition. By increasing the compression ratio and changing the valve timing, it was possible to achieve an average power of 40 liters. With. These motorcycles among the racers were secretly called M-76.



How many modified copies were released in Serpukhov is now unknown, but there were hardly more than ten of them.

Modified version of the M-75M

After analyzing the experience of colleagues from Serpukhov, the engineers of the Irbit Motor Plant set about refining their sports model. The two-wheeled vehicle was thoroughly modernized, having received a new index - M-75M.

The manufacturer has seriously worked on the engine. The very first thing that was done was the rejection of the kickstarter. The ignition system was connected directly from the magneto. Motorcycles were produced and distributed among sports organizations, and work on improvements continued.

Well-known Soviet motorcycle racers sometimes complained that the M-75 engines had one serious design flaw - under maximum load, the cylinders broke away from the crankcase and flew away to the sides.

It was decided to get rid of this shortcoming. As a result, the cylinders were replaced with aluminum ones with a pressed cast iron sleeve with a special composition. This material could expand. It was possible to get rid of the “flights” of the cylinders due to the long through anchor-type studs.

The connecting rods and crankshaft on the M-75 motorcycle were used regular ones from the M-72 model. For the new motorcycle, it was decided to install the lower heads of the reinforced type connecting rods, and carefully polish the rest of the parts. Valve plates have increased from 38 to 40 mm, the inlet and outlet channels had to be expanded.



You need to understand that the M-75M cannot be considered fully serial motorcycles, like its predecessor. These models were assembled on a slipway and improvements were constantly made to their design. The task of reducing the cost has never been - these motorcycles had to win! Plus, the riders themselves usually modified their technique in accordance with their characteristics and habits.

The braking system was seriously changed over time - the standard M-72 wheels were abandoned. The drums received cooling fins and perforations. The holes were covered with steel mesh. Brake pads widened. Stopping technique has become better, regardless of the heating during the competition.

The remaining components of the M-75M motorcycle were also modified, this was mainly expressed in their strengthening. New carburetors appeared in the power system - these were K-95, then K-97. Due to this, the speed was increased, while reducing fuel consumption.

The frame on the M-75 was originally used from the serial "carriages" M-72 without modifications. The upgraded motorcycle received a redesigned design. At first, it was lightened, then they began to be made from round pipes of increased strength.



Judging by the recollections of Soviet riders, the main disadvantage of the M-75M was considered to be a small fuel tank.
If the M-75 was an ordinary refinement of a serial road model, then the M-75M, especially of the later years of production, is a specific sports bike.

M-77

In 1954, the M-77 debuted at competitions. It was a further development of the Irbit Motorcycle Plant models. The engine was improved and developed from 45 to 50 hp. The model was produced until 1959.

But the M-77 was the last sports bike in the 750cc class. In total, about 3 copies were produced. They are considered the best and most perfect in the series, and they are.

It is almost impossible to buy a sports bike from the USSR, which once competed in Soviet circuit races in the 750 cm3 class. They remained only in museums, it is likely that in some private collections.