As a young and fearless motorcyclist in the early seventies, a bourgeoning collection of speeding tickets soon made me realize that truly fast riding should take place on the racetrack, away from public roads and police cruisers. Coincidentally, the ultimate Boy Racer, Yamaha’s RD400, was about to be released. The magazines had tested some pre-production bikes and were filled with glowing reports about the giant-killer: light weight, good handling, ferocious acceleration, top-notch brakes and a very affordable price. I simply had to have one.
Although employed at a Honda dealer at the time, I went to the nearest Yamaha dealer and placed a down payment on their first RD400, sight unseen; I didn’t care what color, I just wanted it ASAP. I worked my way through the Novice, Junior and Expert ranks on that bike, and three seasons later it was still redlining its way around racetracks from New Hampshire to West Virginia, reliable as a stone. Few things in my life have pleased me more than dusting off big Z-1’s and R90S’s on that little 400cc two-stroke.
Eventually, I moved up to higher displacement classes and forgot about the RD, at least until the summer of 1997 when a customer brought a dust-encrusted relic to the service department for resurrection. As so often happens, we were able to get the motor running OK, but our customer bailed when the full magnitude of the project became evident. And so a cosmetically-reasonable, running-but-in-need-of-major-TLC RD400 found its way onto the abandoned-bikes auction block. No bidder was willing to go over $300 -- way too cheap in my mind -- so I took it home.
Then the fun began. Careful detailing stripped away the decades of decay and made the bike look great. I rode it regularly, while doing a step-by-step rehabilitation. New tires, battery and cables were followed by fresh pistons and rings, and other various bugs were systematically flushed out and eradicated. Things were going swimmingly, save for one pesky problem: repeated random piston seizures. Over several seasons, I pursued a cure by re-sealing the bottom end, installing electronic ignition, bigger jets, cooler plugs and, of course, new pistons and rings…I tried everything I could think of. Still, on occasion, the motor would just tighten up. I learned to rest my fingers on the clutch lever, anticipating the next nip-up, until finally I discovered a hard-to-see broken drive pin (a 50 cent part) within the oil pump assembly. AHA! The failed pin caused random reductions in oil delivery, leading to the periodic seizures. I was eight or ten pistons poorer, but now I had my reliable RD.
Arguably, this machine represents the pinnacle of development for the air-cooled two-stroke street bike. The ride is electric-motor smooth, with rubber mounts holding the 180-degree twin. Reed valves help provide a reasonable low-RPM response, but this engine really likes to spin: things get serious between six and eight thousand revs, and the flawless six-speed transmission is great for keeping the engine on the boil. Overall, the bike is small, light and extremely flickable but, somehow, still roomy and comfortable. Very effective disc brakes overcome the lack of engine braking, and corners are welcomed -- especially with sticky tires fitted. The suspension is soft, plush even, but well-controlled. With the stock “sit up and beg” handlebars and huge, well-padded seat, even the longest trips are easy, putting many larger bikes to shame – just remember to stop every 100 miles for gas! Amazingly, it also works great with a passenger. In so many ways, then, the RD400 really is a giant-killer.