Rusty Bradley’s Kawasaki H1RA
With Phil Aynsley
Phil wrote a column quite a while back on Kawasaki’s first 500 cc GP racer, the H1R of 1970 (1970 Kawasaki H1R 500 Triple). Here, Phil thought we could look at the company’s follow-up model, the H1RA.
Fewer RAs were built than H1Rs—about 10 and 60, respectively. Most were sent to the US during 1971. Bob Hanson imported them without forks or wheels, so he sourced Ceriani and Fontana parts for them.
A revised chassis was the major update, together with the items listed below. Dave Simmonds did campaign a H1RA in Grand Prix with one win (Kawasaki’s first in the class), one second and two third places to finish fourth for the 1971 season.
Kawasaki also made upgrade kits that could be installed on the R bikes that included most of the revised/new parts that the RA was equipped with – cylinders, carburettors, electronic ignition and expansion chambers. The kits sold for $550 US. Power was a bit over 75 hp at 9,000 rpm and top speed 257 km/h.
The bike seen here is one of the complete RAs that was supplied to Boston Cycles for their rider Rusty Bradley to race (with Kevin Cameron as mechanic). However, Rusty was killed after colliding with another rider in the first turn of the season’s first race, the Daytona 200.
Boston Cycles repaired the bike (although some crash damage, such as the broken cylinder head fin, remained) before it went to the AMA Museum for many years. As a result, it is the most original H1RA still in existence.
Kawasaki H1RA Racer Specifications
| Kawasaki H1RA Racer Specifications | |
| Engine | Air-cooled, two-stroke three-cylinder |
| Capacity | 498.7 cc |
| Bore x Stroke | 60 x 58.8 mm |
| Transmission | Five-speed |
| Power | 75 hp at 9000 rpm |
| Frame | Double cradle tubular frame |
| Suspension | Telescopic forks, dual shocks |
| Brakes | Four-shoe, four-cam front drum brake, double-cam rear drum |
