Honda has revealed a new, smaller-displacement variation of the 470cc parallel-twin engine introduced on its new CBR500, CB500F and CB500X models. The new engine has a bore of 67mm, just like Honda‘s 500-series engine, but a stroke of 56.6mm instead of the longer 66.8mm. The result is an engine displacement of 399cc, which makes the new engine a better fit for markets such as Japan license restrictions are much stricter for engines larger than 400cc.
While no specific uses for the engine were announced, the new powerplant is expected to be used in a similar line of models as the 500 family. This will likely include a CBR400, a CB400F and a CB400X for Japan.
These new models will likely not replace the inline-four CB400 Super Four and CB400 Super Bol D’Or, which celebrated their 20th anniversary in 2012. The four-cylinder engine has a claimed power output of 52 at 10,500 rpm and peak torque of 28 ft-lb. at 9500 rpm. Honda did not reveal power or torque figures for the 400cc Twin but they should be lower than the 500cc family’s claims of 47hp and 32 ft-lb.
“We approached power characteristics and component configuration with emphasis on precise linear acceleration and deceleration, as well as responsive control in full-body maneuvers like braking and entering and corner exit acceleration,” says Yoshiki Nagahashi, head of the new engine’s development team. “We discussed what makes and engine cool with the design department from the very start of planning, and developed it with the aim of making an engine that would please the majority of our domestic customers while meeting the demands of the development members.
“We focused on the characteristics of the most frequently used low and moderate RPM ranges to make it easy to handle for an entry-level user, and set the maximum RPM at 9,500. We chose a straight two-cylinder water-cooled engine to match these engine characteristics. In order to improve intake performance up to 9,500 rpm, we researched the optimum valve size, and used a bore stroke of 67 mm by 56.6 mm.”
[Source: Honda via Rushlane]
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