Your motorcycle's final drive chain and you.
If you’re anything like me, you didn’t grow up around motorcycles and had no idea how much maintenance they needed. Motorcycles have a lot of systems that need a whole lot more maintenance than cars, and the biggie there is the final drive. Most people never think about driveshafts in cars, but definitely need to think about the way power is transferred to the rear wheel on our motorcycles. All those systems need attention, but they’re also fascinating, and we should take them into account when we’re motorcycle shopping.
Some of the earliest motorcycles had belt drives. Since that was a century ago, those belts were made of leather. Even though the engines that drove them didn’t have a whole lot of power, leather ages and wears and stretches out very quickly, so the belts didn’t last. Eventually, motorcycle manufacturers began to use chains to drive the rear wheel like bicycles. Today, there are three main drive systems on traditional internal combustion motorcycles: chain, belt, and shaft. We’re going to take a long hard look at all three and tell you the ins and outs, ups and downs of each of them. First, we’re going to talk all about chains.
Chains are about the most popular final drive you’ll find on a motorcycle, throughout history and to this day. They have two distinct advantages over the other two drive systems: cost and variability.
Chains are used to drive all kinds of things, from bicycles to garage door openers to clocks; heck, chains have been around since China’s Song Dynasty. Even Leonardo DaVinci used them. “Time-tested” barely covers it. This means not only is the whole chain final drive system inexpensive and relatively easy to make, but anyone who knows anything about mechanics can figure out how they work. They’re simple, and very easy to repair and replace.
Chains are relatively lightweight, too, so they transfer almost all of the power the engine puts out to the rear wheel. You’ve heard people refer to “horsepower at the rear wheel,” right? That’s because there’s some power loss in the transfer of motion from the engine to the tire and what the engine puts out isn’t what’s on the dyno or the pavement. Of the three systems, chains are the most efficient and transfer the most power.
In terms of maintenance, they are the neediest of the drive systems. Common knowledge (and lots of Motorcycle Owners Manuals) say you should clean, lubricate, and check the tension on your drive chain around every 500 miles. I do so sbout every other tank of gas. Lots of people have asked me how long motorcycle chains last and I always say “replace them when they’re worn out,” since chain life has way too many variables to answer that question. Rain, sand, dust, your commitment to maintenance, the heaviness of your right wrist, your tendency to wheelie or do burnouts; all these factors affect the lifespan of your chain and sprockets.
How do you know your chain is worn out? When you can’t get it adjusted properly anymore. Chains don’t wear evenly, so if your chain seems to be tight in some places and loose in others, if you notice it makes excessive noise, or if you can pull it away from the rear sprocket and see daylight between the teeth and the chain, it’s time to replace it.
When you are shopping, you’ll see “o-ring” and “x-ring” chains. That is the shape of the cross-section of the gaskets that seal what is essentially a linked series of bearings. Those gaskets keep the lubrication in and the dirt out of all of your chain’s innards. Wear is a thing, though, and those gaskets, pins, and rollers all eventually wear out. Luckily, chain replacement is relatively cheap and easy. If you have a low-powered motorcycle, a chain with a clip-type master link is just fine. A high-powered motorcycle, though, is safest with a rivet-type master link, and for that, you will need a chain riveting tool.
The chain on your motorcycle arrives stock and optimized for the mid-range of the bike’s performance. The length of the chain and the size of the countershaft and drive sprockets determine the speed of the rear wheel (and therefore of the bike) in a given gear at a given RPM. This can get a little confusing, so we’re enlisting the help of our friends over at Rocky Mountain ATV/MC to help visualize that, in the video above. Changing the gear ratio can make a motorcycle with a smaller engine rev a bit lower and roll a little easier on the highway.
When you change the gearing on your motorcycle, you will need to keep your chain length in mind. A rear sprocket with more teeth might necessitate a longer chain and possibly a different countershaft sprocket too. A smaller rear sprocket will, in bicycle terms, put your motorcycle in a slightly higher “gear” everywhere–that is, the rear wheel will turn faster at a given RPM in a given gear in the transmission. This is what folks mean when they say they want their gearing to be “taller.” But keep in mind that any changes you make to that top end, to get your top gear a little taller, will change the bottom end and make first gear taller as well. That’s all great when you’re on the highway, but if you’re planning to take that same bike down any hinky loose gravel roads, first gear will be faster and might get you into more trouble than you’re prepared for.
Don’t try to reinvent the wheel when you’re considering different sprocket sizes. Dollars to doughnuts, loads of people before you and with your same bike have figured it all out and put some information on the internet. There are calculators, speed per gear at a given RPM tables, and gotchas all over the place. Do your research and you’ll be happier with the result.
Finally, chains are pretty messy. They’re out in the open, they’re covered in chain lube which can and will attract road grime, and they fling the lube around. Wear gloves when you’re handling your chain. Never adjust or otherwise touch it while the bike is running. There are lots of pictures of folks with their fingers stuck between the chain and the sprocket. Be smart about maintenance. Keep your slippery chain lube off your rear tire. Remember while you’re cleaning chain lube off wheels and painted parts, WD-40 makes a great (and gentle) chain-spoo cleaner.