HAVING WAITED for the right moment, the latest 400cc naked 'retrostyle'
bike, Suzuki's Impulse, has been launched here in Japan.
The first Impulse appeared in Japan back in 1982. Based on the
GSX400F, that bike had a Yoshimura 4:1 exhaust system, aluminium swing-arm and
adjustable rear shocks. The second Impulse came out in 1986 with, I think,
rather odd styling by Hans Moult, the father of Katana.
Unlike previous Impulses and the other Suzuki roadsters such
as the Katana and GSF400 Bandit, the third generation Impulse has rather
conventional styling. Nothing surprises at all. The only thing that looks any
different from any of the others is the tank. The angular shape makes it look
as if it has been made of cardboard, but Suzuki says it emphasises its
People's attitude to bikes is changing. There is now less
emphasis on the maximum speed and power of a machine. Instead power delivery
is becoming the most important factor; how well the engine and chassis blend
and how much you can enjoy the bike in any situation. Thanks to the power
restrictions in Japan (400cc bikes are restricted to 53bhp), the manufacturers
have realised they can make more interesting motorbikes with less power.
Suzuki reckons the Impulse is the most sparkling 400 naked bike ever.
I rode the bike in Tokyo for a day and the most remarkable
thing I noticed at first was its massive low-down torque. I started the
engine, clicked into gear, released the clutch lever and the Impulse started
moving very smoothly and reassuringly — not something you expect from a 400cc
The liquid-cooled, transverse-four engine with a 52mm x 47mm
bore and stroke is from the Katana 400 which was already quite powerful in the
low to middle reaches.
Suzuki has given the engine smaller 29mm carbs to improve the
throttle response and deliver even stronger torque low down. The bigger
seven-litre airbox with larger intake ports is a further improvement.
In an awful traffic jam in Shin-jyuku, where many skyscrapers,
including the Tokyo metropolitan building and many sex shops are, the flexible
engine made the bike easy to ride and overtaking buses, taxis and
pizza-delivery bikes was simple. To ride through a traffic jam on a bike, the
engine should work without lagging and have enough torque1 at any revs.
The Impulse achieves this almost perfectly.
In Tokyo there is a highway called Suto-Kousoku. This has a
central circuit and many radial roads extending to the outskirts of of the
city (the toll costs 700 Yen for a motorbike - or about £4.50). I went around
the central circuit on the Impulse in the morning before the mad rush hour and
found the chassis worked quite well with the powerful engine. It has a
traditional double-cradle frame, 41mm front forks and an aluminium swing-arm
which is an 'H' shape in cross section for added strength. The chassis is not
especially outstanding, but it is stiff enough and has reasonable flexibility.
The brakes are superb: two 290mm floating discs with twin-piston calipers at
the front and a 250mm disc with opposed piston caliper at the rear. They
manage to stop the bike quickly before you crash into a taxi which suddenly
turns and stops to collect customers. The handling has no vices and copes
easily with Tokyo riding.
The Impulse is set to be competing against other nakeds in
Japan such as the Kawasaki ZRX, Zephyr 400, Honda CB400SF, Yamaha XJR400,
Suzuki Katana 400 and Bandit 400. It's being said here tjiat Japanese
motorcyclists are in the middle of a naked boom, but my feeling is that it
isn't just a boom. * The naked bike is becoming Japan's standard after having
a racer-replica boom. In other words, we are getting 'back to basics'. Basic
can be anything, like a pair of jeans can be worn in both a formal and an
informal way. The Impulse might not be the most stylish of bikes, but it's
certainly one of the toughest.