A few issues back, I felt like I had run the gamut of topics for these Rumble Tech-Tips. I hit the bottom of the barrel with my highly informative, How to Tie a Doo- Rag tip, and figured the powers that be over at the mega-conglomerate motorcycle publishing empire in Fountain Hills would just cut me loose after that smelly one. No such luck. Since I pandered for suggestions for topics at the end of that piece, I've been buried with e-mails suggesting new subject matter to spew over. It seems there are people intimidated to ask stuff in public that they still want to know the answers to.
I've done my best to keep these "Tips" directed to the novice or non-mechanic type of reader because the statistics show there are a larger number of literate people who would rather ride motorcycles than want to work on their bikes, and that's a good thing. Even though people don't necessarily want to grab a wrench, they seem interested in finding out more about the workings and history of the innovations designed into their machine. Some of you are interested in why or how components in your bike function, so you can have a way to communicate clearly with your tech to better understand the choices offered when a repair rears its ugly head.
There were inquiries regarding belt drives and chain final drives; about which would make a better drive system on their bike. Just like most any comparable choice, there are going to be the ups and downs, pros and cons of an "operating system" like belts or chains. So first I'll take this opportunity to offer a basic explanation of the different variety of parts that transfer the energy of your engine to the rear wheel; your final drive system.
Please bare with me here, your 'final-drive' on an American bike is either a "belt" or "chain" drive, not a shaft. (We'll leave that whole topic for the 'metric' issue.) In the belt drive system; the round objects with cogs on them are called pulleys. In a chain drive set-up; they're called sprockets. Either you have a pulley with cogs that mate to the teeth on a 'rubber' belt spinning off the transmission, or you have a sprocket with teeth that mate to metal links on a chain.
Most every genuine Harley-Davidson motorcycle built since 1984 is equipped with a belt final drive, but there's still a ton of custom American bikes being produced that use a chain to spin the rear tire. So back in the good-old 'buy-back' period (post-AMF Harley), the engineers at the mother factory decided that a belt would replace a chain. Why would anybody build a modern motorcycle with a chain on it? Don't those engineers in Milwaukee know what's best for us bikers?
First let me make a short list regarding the benefits of a belt comprised of a high tech compound, rubber and Kevlar, the same stuff they make bulletproof vests with. Belts don't need oil to keep them lubed up, they weigh less than a chain, can last up to 100 thousand miles before you need to replace them, and they take very little maintenance because they generally do not stretch.
This all sounds great. I'm glad my original Harley had a belt on it. But, the very first day I rode around on my spankin' new 1985 FXWG belt-driven Wide-Glide, I had an old time biker tell me I needed to ditch that 'rubber-band' and get a chain. Some traditions die-hard, a heavy metal chain was the proven way to propel a Harley since the early days, and this old graybeard was going to give me some sage advice. It was time to re-think this new abomination of an innovation, my belt drive.
He told me that my new fangled belt was going to snap on me, and it couldn't be as tough as a chain. If I wanted to change gear ratios, all I had to do was swap out some sprockets, and I could launch my bike from light to light. If my chain broke, all I needed to carry around was a little master link to repair it, and I'd be back on the road. He put the fear of Jesus into me. I would be stranded and I'd be just plain out of luck if I didn't heed his advice and drive directly to his buddies shop. Now was the time to replace that dumb belt with a serious chain.
Lucky for me, I had just spent my last dime on the down payment for my bike. I figured I'd take my chances and run the belt until it "imploded". As it turned out, over the next year of riding with friends in LA, I made the right decision. They all had earlier production bikes with chains. I witnessed these guys constantly dealing with the maintenance problems associated with a chain. There was oil flinging all over their cool custom paint jobs from chain lube. At every stop they pulled a rag out of their back pocket to wipe down their bikes. Before every long ride it seemed they had to adjust their rear wheel to tension up their chains. About every 7000 miles they were replacing their chain with a new one. I even had one buddy install a custom urethane skateboard wheel riding against his chain on a spring tensioner to help stop it from flapping around.
If you think about it, a chain is composed of links of metal, which are constantly tugging apart from the forces; torque and horsepower. Each link on a chain has metal-to-metal contact with each and every link, and then again contact with the metal teeth of the sprocket. If you don't keep a chain liberally lubed, the metal just grinds itself literally to death. This is why their chains seem to "stretch". Combine those issues with abrasive qualities of dust and dirt; the chains just seem to eat themselves right up in no time.
Stock Harley bikes didn't come equipped with O-ring chains, and most of my riding buddies ended up paying as much for their first replacement O-ring chain as it would cost to buy a belt for my new bike. (An O-ring chain was an improvement where at each link, a tiny rubber ring is fitted at each link, which holds the lube in and limits dirt from entering the link.) Add in this fact: you'll need to change both sprockets about every other chain replacement. Then figure in the price of labor to install this stuff too. Now this whole 'rubber band' belt-drive idea seems really cool.
As you can tell, I'm still a believer in the belt drive method of delivering the muscle to the road. So why, you might ask, would anyone put a chain on a new custom built bike if a belt is so great?
I'm glad you asked.
If you're into bike customizing and you want to put a fat tire on a stock bike, a chain is much narrower than a belt. A standard belt is 1-1/2" wide, while a fat modern O-ring chain is less than ¾" wide. This gives you the opportunity to put a tire that's about ¾" wider than your original equipment if you want to pack a bigger tire under your fender. You can "easily" go from a 130mm standard tire to a 150mm, or maybe larger unit, and still fit it on your stock frame. That's really kinda cool, huh?
If you're building a custom bike from scratch and you've chosen a chassis that fits a giant 280mm tire, and you find out that there's a new 300 on the market, there goes your belt, in favor of a chain. Same thing with a 300 chassis, when you want to put a 330 on your scoot; there goes your belt, right into the junk parts bin in your garage. Every time you turn around there's a new fatter tire, and a brand new bike with a chain on it. When will it end? Your guess is as good as mine. In my opinion, it stops being about performance when you cram a tire that's too big for your chassis on to your bike by trading out a belt for a chain.
Right now there's a gear-head reading this about to throw a conniption fit. I know, I know. You put a chain on your bike because you have some monster gazillion horsepower motor and you don't want to snap a belt when you're racing for pinks on Friday night. Good for you. Keep fiddling with your hot rod, old-school drag bike. In the last 16 years of owning a shop, I've sold maybe 3 belts that snapped. One guy removed his belt guard and caught a rock that stuck in his pulley, and the other two were abusing their bikes and snapped their belts when they missed a shift while drag racing, or doing burn outs. None of these three guys had the damage that I've normally seen resulting from sloppy, worn-out chains, grinding on primary covers and tearing up fenders when they snap.
It seems to me the choice is pretty obvious, and I rarely side with the conservative engineers over at HD. They move a little slow sometimes, and the performance aftermarket usually comes up with a better idea. The belt drive on my '85 was one heck of an innovation. Hey, wait a minute, wasn't that final belt drive an aftermarket innovation developed by some old greybeard who wasn't on the Harley engineering dole? The designers over at Harley just incorporated it into their new "Evo" bikes in the early 80's. Now who's old-s'cool?
Keep the rubber side down.
- John at Steeds