In the beginning, motorcycles had drive chains to transfer the power from the engine to the wheels, just like the chain on a bicycle. No surprise there, considering that at first motorcycles were essentially motorized bicycles. Cars, on the other hand, handled that transfer of power using a drive shaft. It was probably inevitable that eventually some motorcycles would be driven by a drive shaft and today that is the case.
So, is one better than the other? And if so, why don’t all motorcycles use one or the other? If not, how are they different and why do some bikes use a chain while others use a drive shaft?
The answer, which you may have suspected already, is that each is better in some ways than the other, and the manufacturer’s decision to use one or the other is based on several factors.
My first bike was, in its day, a big (750cc) touring machine, and it has a chain. I say “has” because I still have it and I still ride it, even though it is more than 30 years old. When this was my principal (read: only) bike I knew when we took off on our summer road trips that every one or two days I would need to lubricate and adjust the chain. It was a pain but it was just part of what riding a motorcycle entailed. And then, every couple years or so I had to replace the chain and sprockets because they wore out. That was not a welcome expense but, again, it came with the territory.
My next bike, a 1999 Kawasaki Concours, has a drive shaft, and also a lot more power. This is the ride-all-day-at-high-speed bike my first bike never could be. And I never give the shaft a moment’s thought, any more than I think about the pistons or the oil pan. It’s there, it does its job.
So why don’t all bikes just use drive shafts? There are several answers.
First off, drive shafts are a lot more expensive than chains. Second, they’re a lot heavier and bulkier. That translates into them being badly matched to really small bikes. No one wants to pay big bike prices for a small bike. And the extra weight would just rob power from what is already a small engine.
Dirt bikes are a perfect example. Take the Yamaha YZ450F for example. This is a bike weighing 245 pounds with a full gas tank. It holds 1.6 gallons of gas. With a tank that size you don’t want extra weight. Plus, with a chain you can change the sprocket size, which changes the gear ratio, to affect power delivery. In other words, you can tune the bike to your own riding style and preferences.
Then there is that issue of the smaller engine. Chain drive actually delivers more of the power to the wheels. Shaft drive robs power and with a small engine you want to use as much of the engine’s power as you can. If you’re on a big cruiser, such as the Yamaha FJR1300A, you’ve got a 1298cc engine. That’s power to spare and you can afford to sacrifice a little of it in exchange for the shaft drive.
Now, sport bikes have a lot of the same considerations as off-road bikes. They’re small but powerful. Generally sport bikes, such as the Yamaha FZ8, use chains. Power is a big thing for sport bike riders, so low weight and full utilization of all the horsepower the engine can produce is important. And again, especially if the sport bike riders want to hit the track and do some racing, the ability to adjust the gear ratio is especially important.
The bottom line here is that this is not a decision you are generally going to have to make. You get to decide what kind of bike you want, and then you take that bike with whatever gear the manufacturer has put on it. And considering that they probably know a lot more about the trade-offs than you do, that’s probably just fine.