Motorworld’s newspaper № 17
Test-drive video
Nihon Nai-Enki started the manufacturing of 1260 cc Kurogane motorcycles in 1937 on request from the Japan Army. The Kurogane’s big brother was Rikuo Type 97, which was extremely popular among the military. A not well-informed person could easily got 1260 cc Kurogane mixed up with Rikuo, but that’s no wonder because the former is virtually a follow-up revision of the latter.

Kurogane got his “two-storey bike” nickname for a good reason. Having a 20 cm ground clearance, it was one and a half as big as Rikuo! Steering & operating such a big machine in solo was a challenge for the vertically challenged Japanese, so all motorcycles had sidecars. However, stately proportions were worthwhile. Due to sophisticated & executive look, Kurogane motorcycles were mainly used for the conveyance of officers (follow a link to see) the military model).

The Nihon Nai-Enki works was located at Hiroshima; after the nuclear attack, it was ruined along with its total output. Nothing much was known about 1260 cc Kurogane for a long time. Martin Rosenblaum, an on-staff historian at Harley-Davidson, considered this machine is just a myth.

At one time Kurogane was seen at American TV. It has been spotted in the “I Love Lucy” series (popular series in 1951-1957). Unfortunately, no full background for this one exists.

The numerical designation of the Japanese military equipment was based on the year when the model was adopted for armament, according to the date “from the foundation of the Empire” (660 BC). Before 1940 (3000 according to the Japanese calendar), the full designation (four digits) or the last two were used, so the models of 1937 were named “type 2597”, “2597” or “97”. Models of 1940 – “type 100″. Since 1941, only the last digit was used in the designation, for example, 1942 models were named “type 2”, 1943 – “type-3”, etc.

The motorcycle hosted in the collection was produced in Japan in 1939 and intended for the Japanese elite. After the War, it was lost (most probably, it was shipped by sea tothe USA by a Yankee soldier), found in California in 1960 and hidden from the whole world for 30 years until it was again found by Steve Rainbolt, a collector from San Diego who restored it. On 11th October 1997, Kurogane got the “Contest judges’ choice” prize at the international bike show in Del Mar, California. This fact is curious because the bike wasn’t working – Rainbolt restored only the appearance and painted the body into colors of his own preferences. According to what Rainbolt said, at first, he painted the bike into American military khaki, looked at it, realized that don’t like it and decided to repaint the machine. Definitely, such a flippant attitude was unacceptable for a serious collector, but Rainbolt was an amateur. Nevertheless, we should give proper respect to him as a repairman. In spite of an inauthentic appearance, the bike couldn’t be passed over by the judges – it’s the rarest bike on Earth!

Manufacturer Nihon Nai-Nenki, Japan
Years of manufacture 1935 – 1945
Quantity produced, units N/A
Price 2 680 ¥
Today’s value
Type V-twin
Engine capacity, cc 1 260
Bore and stroke, mm N/A
Engine rating 24 hp
Sparking Magneto Mitsubishi
Carburetor N/A
Battery 6 V
Clutch Dry
Transmission 3-speed
Frame type Tubular
Front suspension Springer
Rear suspension Rigid
Brakes Drum type
Wheel size 4,75/5,25 х 18
Length, mm
2 700
Width, mm
1 700 (с коляской)
Height, mm
1 168
Wheelbase, mm
1 650
Ground clearance, mm
Seat height, mm
Mass, kg
   500 (с коляской)
Gas tank size, l/td>
Maximum speed, km/h
Range, km

* – Data from the results of the measurement of the “Motorworld by V.Sheyanov” exhibit.