Strict Standards: Only variables should be assigned by reference in /home/classicyams.com/www/administrator/components/com_acesef/library/factory.php on line 22 Strict Standards: Only variables should be assigned by reference in /home/classicyams.com/www/plugins/system/acesefmetacontent/acesefmetacontent.php on line 115 yamaha-125-cc-factory-racers | race-bikes
Strict Standards: Non-static method JSite::getMenu() should not be called statically, assuming $this from incompatible context in /home/classicyams.com/www/templates/constructionco-fjt/index.php on line 94 Strict Standards: Non-static method JApplication::getMenu() should not be called statically, assuming $this from incompatible context in /home/classicyams.com/www/includes/application.php on line 539

Yamaha 125 cc Factory Racers

Print
Published Date

The development story of the 125 ccm Yamaha Factory machines is very interesting as it started out with very simple machines.

The first 125 cc "racer" was a "tuned" version of the standard YA1, the "Red Dragonfly" I have to search of course for pictures of the missing models, but they will be added later.

Here is a list with all the real "Works" machines and their codes:

(Please note that the YA1 was a simple "tuned" standard production machine, used for a "primitive" form of racing)

yr code cyl cool ind bxs hp/rpm ign clut carb sp
55 YA1 1 air pist 52X58 5,5 mag wet
55 YA1 1 air pist 52X58 10 mag wet
57 YA-A 1 air pist 54x54 14 mag wet aml27 4
57 YA-B 1 air pist 56x50 14 mag wet aml27 4
61 RA41 1 air rot. 56x50 20/10.000 mag dry 2mik/aml 6
62 RA55 1 air rot. 56x50,7 22/10.500 mag dry 2mik/aml 6
63 RA75 1 air rot. 56x50,7 25/12.000 mag dry m34 8
64 RA97 2 air rot. 44x41 34/14.200 mag dry vm25 8
65 RA97 2 water rot. 44x41 34/14.200 mag dry vm25 8
66 RA97 2 water rot. 44x41 38/14.700 mag dry vm25 9
66 RA31 V4 water rot. 35x32,4 38/14.700 mag dry vm22 9
67 RA31 V4 water rot. 35x32,4 40/17.000 mag dry vm22 9
68 RA31A V4 water rot. 35x32,4 44/17.300 mag dry vm22s 9
69 YZ623 2 air pist 43x43 28/12.750 mag wet vm22sh 5
70 YZ623 2 air pist 43x43 30/13.750 mag wet vm22sh 5
71 YZ623A 2 air pist 43x43 31/14.000 cdi wet vm28sc 6
72 YZ623C 2 water pist 44x41 32/14.250 cdi dry vm28sc 6
73 OW15 2 water pist 44x41 34/14.250 cdi dry vm28sc 6
74 OW15 2 water pist 44x41 35/14.250 cdi dry vm28sc 6
75 OW15 2 water pist 44x41 38/14.500 cdi dry vm28sc 6
76 OW37 1 water pist 56x50,6 40/14.000 cdi dry vm34sspj 6
77 OW37 1 water pist 56x50,6 42/14.000 cdi dry vm34sspj 6
78 OW37 1 water pist 56x50,6 44/14.500 cdi dry vm34sspj 6

 

The first really built for racing bike was the Works Asama 125 cc racer for 1957. A very special story will be made of these very early machines. The picture is from the start at the actual Mount Asama race in 1957!

CLICK

The Yamaha RA41 G.P. machine was the first works racer built to race on the European G.P. circuits. The prototype was called YX41, a single cylinder engine with 2 rotary valves, which was used during the mid '61/end '62 period.

 

Yamaha RA41 1961
Yamaha RA41 1961

The machine specifications also included the already famous Yamaha Autolube Sytem (you can see the pump on top of the crankcase). Even one of the two carburettors can be seen.

CLICK

By the end of 1962 the RA55 replaced the RA41 (November 1962) shortly as it was more a testbed for the RD56 twin 250 ccm racer to come.

 

Yamaha RA55 1962
Yamaha RA55 1962

The 1963 racer was named the RA75. It had an 8-speed gearbox and was used quite extensively. It was still a single, breathing through 2 big Mikuni M34 carburettors (again 2 rotary valves).

 

Yamaha RA75 1963
Yamaha RA75 1963

Here are some details of the RA75

 

Yamaha RA75 1963
Yamaha RA75 1963

The RA97 arrived on the circuits by mid 1964, preceded by the experimental YX97 machine. This new twin cylinder bike had a bore/stroke of 44 x 41 mm, a dimension which Yamaha would abandon later but after much consideration re-used in 1972. The first “generation” of the RA97 was air-cooled.

Yamaha RA97 1964
Yamaha RA97 1964
From the details the relatively wide construction of the rotary valve engine can be seen, including the “bulbeous” cowling that also was fitted to the later 250 cc machines.
Yamaha RA97 1964
Yamaha RA97 1964
The second version of the Yamaha RA97 of early 1965 was already water-cooled. The intricate “plumbing” of the little machine can be clearly seen here.
Yamaha RA97 1965
Yamaha RA97 1965
Yamaha Japan still has one of these beauties in their collection.
The last RA97 is practically identical, the clutch was improved and power was slightly up.
Yamaha RA97 1966
Yamaha RA97 1966
Also the tachometer drive got a different place.
Yamaha RA97 1966
Yamaha RA97 1966
By the end of 1966 the fantastic V-Four RA31 was introduced. The first machine had very similar power to the latest RA97, but this was quickly “pumped-up” to 40 PS.
Yamaha RA31/A 1967
Yamaha RA31/A 1967

The RA31 was followed by the Yamaha RA31A, ultimately with 44 PS at 17.300 rpm.

 

When the Japanese factories pulled out of G.P. Roadracing by the end of 1968, Yamaha wished to continue anyway in some form. It was decided to build small series of machines utilizing standard components and some “special” bits. The first machine was the YZ623, actually a TA125 prototype (which arrived only in 1973). The YZ623 was (at first) based upon the AS1 “GYT” kitted racer and given to Yamaha Importer selected riders. The Dutch Yamaha Distributor got a few for the just founded MRTN team (Motor Racing Team Netherlands).
Yamaha YZ623 1969
Yamaha YZ623 1969
The details show the (later) TA125 similarity with the DS6 front brake/CS5 backplate.
Yamaha YZ623 1969
Yamaha YZ623 1969
Cees van Dongen, the Dutch Importer’s chief mechanic, converted the AS1 based racer su much that it bore striking resemblance with the YZ623.He had quite some success with it.

The Autolube pump drive was used to drive the tachometer.

 

Yamaha AS1/3 YZ623 copy 1969
Yamaha AS1/3 YZ623 copy 1969
In 1971 the YZ623A arrived, now based upon the AS3 engine and much stronger/faster. This was the machine taken by the late Kent Andersson for further development. Pictures follow.
The YZ623A was air cooled and many of the private riders were already converting their machines to water cooling as you can have seen in the story about the 125 cc production based racers. Kent Andersson converted the engine as well and Yamaha responded by fitting a beautiful water cooled conversion to the 1972 YZ623C model. This is Chas Mortimer's machine, he used right hand gear change. The first YZ623C machines still had a wet clutch as you can see.
Yamaha YZ623C 1972
Yamaha YZ623C 1972
Another proof of the bike being Chas Mortime's mount! The rear brake is on the left!
Yamaha YZ623C 1972
Yamaha YZ623C 1972

The second lot of YZ623C racers arrived a few months later and were photographed here in front of the Amsterdam garage of my boss, Mr. Ishibashi. Imagine that today, parking works machines in a normal garage in the city!.

Pure coincidence, again the machine for Chas Mortimer. Riders were now sponsored by European Yamaha Distributors and Chas had DANFAY Distributors (Ireland) as back-up.
Yamaha YZ623C 1972
Yamaha YZ623C 1972
Kent Andersson’s World Championship winning machine of the 1974 season has a proud place in the Yamaha collection.
Yamaha OW15 1974
Yamaha OW15 1974
You will agree that this is how a motorcycle should look !
1975 was the last year Kent Andersson rode the OW15, the ultimate version, now also equipped with disc brakes on the front. You see Kent just above the fueltank, talking with Harold Bartol, the equally famous Austrian tuner/engineer. Kent Andersson was the only rider who rode all Yamaha factory twin cylinder 125 cc racers between 1969 - 1975!
Friday the 24th. Joomla Templates Free. Classicyams.com, 2012, copyright Remko Visser