Kawi2strokes.com Forum

There was an article in 1975 or so in an Australian rag (AMCN if I remember correctly) about an S2 or S2-A which had been tuned for racing but reconverted for street use. I should have it somewhere, perhaps I should dig it up.
This conversion is very nicely done and makes a refreshing change from all those boring Yamahas. Sadly nothing came of a planned production S2-R which was rumoured to be under development when the S2 was introduced.

136 kg is not a bad result at all, it's about the same as a 1970 H1-R. Yamaha claimed a dry weight of 110 kg for the TR3. Still, there is scope for getting it down with a bit of work, the kickstarter and shaft can easily be dispensed with for instance. Wonder how much power it makes. Kawasaki claimed 45 hp at the crankshaft and it shouldn't be too hard to get that up to 55-60 hp.

That factory "45 hp" turned out to be 31.8) at the rear wheel........

_________________
Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

The Dutch magazine "Motor" published a roadtest of an S2 in their issue № 35 for 1971. The test included a dyno test at the Technical University of Delft, which recorded 41.5 DIN-hp at 7300 rpm, with max torque of 4.1 kgm at 7,000 rpm. The graph included the hp curve of an A7 tested on the same dyno a few years earlier for comparison purposes, with a max power output of 39 DIN-hp at 6,800 rpm, though with a better power at lower rpm than the S2- no doubt due to the disc valves.

The S2's here were barely faster than the RD's, so I think the 32 rwhp might be closer to the truth. And all the mags laughed at the 45 HP figure.......

_________________
Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........

More figures from the "Motor" test; apart from fitting a 16-tooth front sprocket instead of the standard 14, the bike was unmodified though fitted with the standard low European bars.
Average top speed in two directions 167 kph, maximum recorded in one direction 172 kph. Weather was dry and almost no wind; rider 185 cm tall, 90 kg weight, dressed in racing leathers.
Top speeds in the gears at 8500 rpm: 1st 58 kph, 2nd 92 kph, 3rd 122 kph, 4th 147 kph, 5th 172 kph.
Tach was calibrated and found to be accurate, speedo was off by 10 kph at 50 kph and 13 kph at 170 kph.
I'd have to check whether "Motor" published a test of the RD350; I know the German mag "Motorrad" tested an S2 but unfortunately I don't have that test

speaking from experience, similarly modified aircooled rd and s2 will run almost dead even until the yamaha gets into 6th gear, which is when it walks away. Im taking good chambers, carb mods, etc real world street bikes.

I cant imagine how peaky that bike must be w/jacked cyls and cut intakes but it def revs great. sounds flat out nasty but i bet it would be a nightmare on the street. track though.. which was the intent... probably awesome.

very well done and def different.

It might be fairer to compare the S2 and the RD350's predecessor, the R5, as both have a 5-speed gearbox and piston-ported engines. The RD's reed valves and 6-speed cluster do give it an advantage as both would allow more radical tuning. Plus that there was much more tuning info available for Yamahas thanks to the company's extensive involvement in racing.

Agreed,,lets face it after 1972 Kawasaki pretty much gave up on the two stroke triple concept and developed it to meet regulations rather than break boundaries in performance..

Will see what happens when the S engine gets treated to some modern trickery it seldomly gets.
To beat the faster RD's.... that will be the challenge.

_________________
Speed is what’s life about.