QUESTION: I see the new Honda Africa Twin is powered by a parallel twin, not a V-twin as in the previous bike. What advantages does this arrangement offer? And what potential disadvantages?

Ben Sember

CycleWorld.com

ANSWER: My first interest here is the 500-pound weights of the bikes in this ADV class. Should they be renamed “off-road tourers”? With all that “downforce,” they need all the displacement the makers are giving them.

My first thought: Honda might have been able to reduce the wheelbase a bit with a parallel twin versus the previous V-twin, but both chassis are 62-inchers. Second: There surely are some production economies in a parallel twin: fewer camshafts, only a single-cam drive, a single-cylinder block, etc. Costs are important in the present market.

Another point: A parallel twin packages well. The usual claim for V-twins is that they are narrow, but in fact once an alternator is put on one end of the crank and a primary drive on the other, the overall width could be achieved just as easily with a parallel twin. So, with two (more or less) vertical cylinders, the engine can go forward toward the front wheel, and there is no rear cylinder and exhaust pipe claiming space to the rear, making some volume available behind the cylinders.

Some will note that this parallel twin requires a balancer, which adds complication, but the only balanced V-twins have (1) a 90-degree V-angle (Ducati, Moto Guzzi), or (2) not-so-durable offset crankpins (Honda Ascot), or (3) twin balance shafts (Aprilia RS1000). As engines are made bigger in displacement, piston-shaking force increases.

I’m glad to see that a DCT is offered because I’m all for reduced operator workload. The new Africa Twin’s two crankpins are set at 270 degrees. This gives the exhaust a V-twin-like syncopation, and some will argue that it benefits traction. The traction argument is this: With 360-degree crankpin spacing, both pistons are stopped together at top and bottom center, imposing an inertial “flutter” on crank speed, as the two pistons take energy from it as they accelerate and give it back as they decelerate. But with the 270-degree spacing, when one piston is stopped at TDC or BDC, the other is at close to maximum speed in mid-stroke, so the pistons exchange energy with each other, not with the crank. But how can we know?

(By Kevin CameronCourtesy of Honda December 3, 2015)