In the 125s there was a fierce rivalry between four-stroke and two-stroke riders. This is clearly illustrated in the Joe Bar Team's first album. However, this does not refer to charming old-timers such as the already outdated Jawas, but to Japanese two-stroke engines. One of the most famous motorcycle manufacturers, Yamaha, known for the crossed tuning forks logo, made some impressive machines. After Yamaha discovered the two-stroke secret by looking closely at models such as the DKW's RT 250cc and the Adler 350, the brand came up with cylinders with five flush ports and separate oil injection. The Yamaha RDXNUMX.
Yamaha RD350. With Oil Injection
This innovation resulted in more power (thanks to two extra purge ports) and better performing and more thermally stable engine blocks. The Autolube oil system put an end to self-mixing of oil and gasoline, as well as filling questionable fuel mixtures from the pump. Yamaha's technology produced fast and reliable two-strokes. In addition, all of these machines paid homage to the world championships Phil Read had achieved on Yamahas. The Yamaha RD350, at the time considered a medium duty bike with its 350 cc, represented the pinnacle of Yamaha's expertise in air-cooled two-stroke engines and high-quality finish. At the time, there were certainly buyers who appreciated the RD350's touring qualities and smooth nature. The Yamahas were far from weak, and the RD350 had more racing DNA than many a modern sport bike.
After all, the letters 'RD' stood for 'Race Developed'.
The frame of the Yamaha RD350 was almost identical to that of the TZ250-350 production racers, with only a two-degree difference in the head tube angle. The 347 cc engine block delivered 39 hp thanks to Yamaha's 'Torque Induction'. Until just a few years earlier, the now very expensive BMW R69S with 42 hp from 590 cc was the fastest production motorcycle in the world, with a stated top speed of 170 km / h. The same top speed was credited to the Yamaha RD350. And why did more Yamaha RD's die than BMW R69S's? That's because most RD350 riders believed they were descended directly from famed World Champion Phil Read.
Yamaha RD350. The Giant Killer
The nickname “Giant Killer” was given to the RD for a reason. When the throttle was fully opened, the two-stroke twin shrieked like a chainsaw with serious heartbreak. Owners determined to give it their all mounted fairings, clip-ons or the famous 'lop-ear handlebars', as well as exhausts from legendary brands such as Ack Bant, Bullet, Reimo or Gianelli. These exhausts marked the end of the comfortably wide rev range in which the RD excelled, but delivered significant power gains. Unfortunately, they also often ensured the eventual end of the tough engine blocks. The expansion exhausts (often in combination with modified air filtration) required significant carburetor re-tuning. This was sometimes hastily forgotten, leading to burnt piston heads.
Parts Availability
Parts availability for the Yamaha RD350 is reasonable. However, NOS (New Old Stock) is becoming rare and comes with a price tag. The Dutch CMSNL.com is a worldwide supplier of parts. Bang to Potz also has a lot of technical parts. However, it is advisable to buy a copy that is as original and complete as possible. Prices for a neat copy are between € 3.500-6.000. The trend is rising.
Technical Specifications
Yamaha RD350: Two-cylinder two-stroke, 347 cc, compression ratio 6,2/6,6:1, carbureted 2x Mikuni VM28 SC, six-speed, 39 hp at 7.500 rpm. Top speed: more than 160 km/h.
Hey Niels, fully synthetic is too thin for the blocks of the air-cooled RDs from the 70s, but for my RD LC YPVS from 1985 I use fully synthetic blocks that run excellently! Kind regards, Nicolas
In my hometown, someone with the latest LC generation drives many a supersport driver (M/F/O) with great pleasure..
However, preference is given to the old ones air-cooled: 250, 350 and 400.
Actually, the last series of technies were even more beautiful.
YPVS, Yammerja Power Valve System, later also on the Suzuki RGV and the Aprilia RS250 have 2-stage valves (slides) in the exhaust port to regulate the purge at idle and high rpm.
With the RD500 it was even a 4pitter 2 stroke. .. . . .
Suzuki and Aprilia had a stepper motor on their 250 cc 2-cylinder models for those valves.
The 125 cc 1-cylinder models often had a solenoid (magnet) control for it
Incidentally, more and more 2-stroke drivers disconnect the oil pump, and then refuel 1:50 with a good full synthetic.
Yes, and you have to mix it yourself.
In the past, the oil sometimes wanted to “separate” in the tank during self-mixing, but with the domestic oils that is a thing of the past.
In addition, the oil pumps or gas cables to the pumps sometimes die, and they often lubricate quite richly (due to the poorer types of oil at the time.)
What's wrong with an oil pump, that more and more riders disconnect it and mix it themselves? Those pumps were certainly not created to eliminate self-mixing, but to inject the oil directly so that it mixes less with the fuel and the oil therefore settles directly on the moving parts and will do its job better. Less oil needed for better results. Such a pump naturally requires inspection and maintenance. Forgetting that already caused many a pump to fail and euthanize the engine block immediately. The race teams in the time of Mitch Doohan and associates certainly did not work with mixed lubrication and that was not without reason. Even something like a Trabant worked with an oil pump, you can check.
I had the 250, why not mention it here? I think it sold a lot too. Enjoyed it very much, but it was impossible to drive it quietly with that thing. Always begging for full throttle, he did. Nice but also link, because you often lacked a bit of power. 33 hp is ok if you are not in too much of a hurry. They sure were beautiful!
I rode around on a Suzuki GT80 (two-cylinder two-stroke just like the RD500) in the early 350s. A good acquaintance of mine drove the RD350 at the time ... and I had all the trouble to keep up with it ... I could handle it on power, but the RD clearly steered better than the Suzuki (despite reinforced rear fork and red Koni's)
I still think back fondly on this time…we had a lot of fun with these bikes…
Truthful account of the RD350, drive it yourself (type 521 from 1975), very smooth engine for touring, I did remove the oil pump and mix 1:50 with semi-synthetic 2 T oil (pump had the reputation of often falter!). Nice, smooth bike, highly recommended!
Why a semi-synthetic oil, not a full synthetic?