Service
SERVICE
PAUL DEAN
A new kind of power
Q I have a bucket full of water at the bottom of a well. A rope is attached to the bucket at one end and a winch at the other. I apply X amount of force to the winch handle (torque) and wind the bucket to the top in 20 seconds. Drop the bucket in again, refill it with water and apply the same force to the handle but wind it faster. This time, the bucket comes up in 10 seconds. I applied the same torque both times but produced twice the horsepower the second time. Using that example, have I got the general idea of the relationship between torque and horsepower? (I didn’t do the math, so it may not be twice the hp, but it would be more hp from the same torque.) Will Thomas Submitted via America Online
A Lean forward, Will; I need to paste a gold star on your forehead. Even though you didn’t “do the math,” your assumption is correct. If you can perform the same work in half the time, you have produced twice the power. The simple formula for calculating power is: Force x Distance Time. Let’s say you used 15 pounds of force on the winch handle and the depth of the well is 50 feet. In your first example, you raised the bucket in 20 seconds, so we multiply 15 times 50 and divide by 20 to get 37.5, which is how much power you generated. You then raised the bucket in 10 seconds, so we again multiply 15 by 50 but now divide by 10 and get 75, exactly twice the amount of power.
Notice, however, that I only used the term “power” rather than “horsepower.” Power is a general term that can describe the rate at which many different kinds of work is done, whereas horsepower is a specific type of measurement most often used to quantify an engine’s output. Horsepower is a term that 17thcentury inventor James Watt came up with to describe the amount of work that steam engines could produce compared to what horses could do, and it has stuck with our society ever since. What’s more, in 1889, The International System of Units officially named another unit of power, the Watt, after him.
So, if that is how units of power are created, maybe you could fabricate yet another measure and name it after yourself. It would be based on the amount of work involved in raising a bucket of water from a deep well. You could call it... Willpower.
A matter of avoirdupois
Q Using the example in the “Getting over inflation” question (January, 2011) posed by François Payen—whose bike happens to be similar in weight and recommended maximum tire loads to those of my ’82 Suzuki GS 1100GL—I must not understand what the term “maximum load” actually means. I have often thought of past occasional full and rapid stops or slowdowns and what weights are being distributed to the front tire. It would seem that the rear tire is mostly relieved of any weight load in these situations and that the full weight (+/800 pounds, bike/rider/full bags) of my bike is being thrust onto the front tire—not to even consider what additional momentum forces could be compounding this load. So, should I conclude that the max rating for a front tire must be for a bike at rest but that the tire is built for significantly more weight-bearing loads than that? Or should I be putting duallies on the front? Thomas Martin
Bend, Oregon
A No need to spring for a second front tire and wheel; the forces you describe will not damage your bike’s front tire in the least. If a tire has a GAWR (Gross Axle Weight Rating) of, say, 500 pounds and momentarily is weighted with 501, it doesn’t explode or begin to unravel; it just keeps on keepin’ on. The same holds true if it is loaded with most or all of a bike’s entire weight for brief periods. The ratings determined by the tire companies and motorcycle manufacturers take into account real-world factors that include weight transfer of a fully loaded bike onto the front during hard braking and onto the rear during maximum acceleration. Even deep-lean cornering can briefly subject tires to loads that exceed their GAWR with no ill effects.
Instead, what damages a tire is being overloaded continuously. When the total weight of rider, passenger and any other on-board cargo exceeds the bike’s GVWR or either of its tires’ GAWR by a considerable margin and the duo heads out on the road, that’s a tire problem in desperate search of a time and place to occur. This is especially a concern with the rear tire, which, given the rearward location of passenger and luggage, has to support the vast majority of the aforementioned excess weight. Overloading makes a tire flex to a greater extent than intended, and higher speeds on the open road cause it to flex much more often in any given time period than it does when just cruising around town. Flexing more often and to a greater degree generates excess heat and carcass breakdown that can cause the tire to fail.
Despite recommendations issued by the tire companies and warnings prominently highlighted in motorcycle owner’s manuals, overloads like this take place all the time. Sometimes, the results are disastrous. In your case, though, if the entire weight of your GS 1100GL— including you, your loaded saddlebags and a full tank of gas—is truly in the 800-pound range, you have nothing to worry about. Even during hard panic stops and full-throttle acceleration.
No pain, no R6
Q I and purchased put 9800 my miles first on road it in bike the first season. Most of my riding is the local canyons, and I hope to enjoy a few track days at nearby Miller Motorsports Park, but once or twice a year, I take a three-day ride. My Yamaha FZ6R is a terrific first road bike, but now I want slightly more horsepower and torque. My mind is set on replacing my FZ6R with a Yamaha YZF-R6. Friends and dealers tell me that the R6 is too uncomfortable for long distances due to the low position of the handlebars and recommend instead a Yamaha FZ1. Is the low handlebar the only reason the YZF-R6 would not be a good bike for a 1000-mile ride? Eric Leonhardt
Salt Lake City, Utah
AI can’t answer that question with a very high degree of accuracy because I know nothing about your physical makeup, the condition of your joints or your threshold of discomfort. Some riders can cheerfully endure the full-tuck ergonomics of a repli-racer sportbike for days on end while others are a sorry collection of aching forearms, throbbing knees and piercing lower-back pain before the engine reaches full operating temperature. For the most part, the only way to determine in which category anyone fits is to have them climb aboard the bike in question and ride it for a while.
With the YZF-R6, the low, clip-on handlebars aren’t the only potential source of long-ride discomfort; the footpegs are high relative to the seat, forcing
a sharp bend in the knees. Not only that, you claim to want more horsepower and torque, but the R6 has the least amount of low-end and midrange torque of any of the middleweight sportbikes, and certainly less than the FZ6R you now own. The R6 makes impressive horsepower for a 600, but only at very high rpm; in the lower two-thirds of the rpm range, the torque output is so soft that achieving any kind of meaningful acceleration at those engine speeds generally requires at least one downshift, but often two or three.
As a track-day bike, a racebike or a canyon carver, the R6 is superb. As an everyday commuter or all-around day-tripper, it’s quite capable, though a distinct compromise in rider/passenger comfort. But as a multi-day travel companion, the R6 is far from ideal. Only you can decide how much comfort you’re willing to sacrifice two or three times a year in order to enjoy what the bike has to offer the rest of the time.
Look at it this way: Imagine what your answer might be if, as you conclude your first three-day trip, you ask yourself a simple question about the ride: Am I sad that it’s over or glad that it’s over? If the answer turns out to be the latter, you might regret having bought the R6.
Chain mail
Q I new am chain interested and sprockets in installing on a my ’85 Yamaha XT350 supermoto bike.
The bike has a tiny 428 chain, which is weird in itself, but it also has a 19-tooth countershaft sprocket, the largest I’ve ever seen. Why is that? The XL, DR, SP and even TT350s of that era have 14-,
15or 16-tooth sprockets. Why does the XT have a 19? As long as I maintain the same gear ratio, would it hurt if I went to a 14/40 or 15/43 sprocket combination? And should I convert to a 520 chain?
Andy Schmersahl Coopersburg, Pennsylvania
A The decisions that dictated how that bike was built were made at least 26 years ago, and no one at Yamaha today can explain why it had a small chain, other than to presume that the engineers at that time evidently felt that a 428 was perfectly adequate. Also, in terms of “largeness,” a 19-tooth sprocket for a 428 chain is not appreciably bigger in diameter than a 16-tooth sprocket for a 520 chain, simply because the size of and distance between the 428’s teeth are smaller.
In a chain’s numerical designation, the numbers represent its dimensions in Vfc-inch increments. The first number (the 4 in 428 and the 5 in 520) indicates the chain’s pitch (4/s-, or Vi-in., for the 428;
FeedbackLoop
Q In regard to the problem Darryl Burkhardt has with his Kawasaki KLR650 intermittently stumbling and cutting out (“No-purpose dual-purpose,” May issue): Your suggestions were perfectly valid, but another thing that can make KLR650s lose power and seem to run out of fuel is an issue with the vacuum line that runs between the intake manifold and the vacuum-operated fuel tap. In hot weather, my ’96 KLR would sometimes seem to run out of gas, although there was plenty in the tank. I eventually traced it to a soft vacuum line that would slowly collapse from the engine vacuum. Eventually, the fuel tap would lose vacuum altogether, shutting off the fuel flow. Stopping and restarting the bike would release the collapsed line, and then everything might be normal for a number of miles or even days. Replacing the original vacuum line with a piece of hose that had much greater wall thickness completely solved the problem.
Larry Sanford
Submitted via www.cycleworld.com
A Excel lent input, Larry. Not all motorcycles or manufacturers use the very same size and quality of hose for that purpose, but your tip nonetheless could be valuable information for anyone who has a fuel-starvation problem on a bike with a vacuum petcock. Thank you very much.
Vs for the 520), which is the center-tocenter distance between the rollers. The second number is the width of the rollers, so for the 520 chain, that would be Vs-, or í/4-in. The “8” in the 428 number, though, requires a separate explanation. The standard chain with a Vi-in. pitch is either a 420 (rollers lA-in. wide) or a 425, the “25” indicating that the rollers are two-and-a-half eighths (5/i6-in.) wide. The rollers on a 428 chain also are 5/i6-in. wide, but the “8” indicates that its rollers also are marginally larger (don’t ask me how they came up with the 8) in diameter for added durability. Otherwise, the two are the same.
Another chain factoid is that for any given application, the larger the sprocket, the less wear and tear on the chain, and the fewer frictional losses, as well. So, too, do chains with a smaller pitch offer reduced wear rates and frictional resistance. When you add that all up, the idea of a 428 chain with a 19-tooth countershaft sprocket on your 350 doesn’t seem so terrible after all.
Changing your XT’s sprocket combinations and/or converting to a 520 chain should create no problems, even if you alter the final-drive ratio. Just ensure that the chain has adequate clearance around the front sprocket and sprocket cover, especially if you use a 14-tooth countershaft sprocket and a 520 chain. The sprocket will be smaller than the original, and the chain’s sideplates are larger, possibly allowing the plates to drag against the engine case behind the sprocket.
Bottle shock
Q Recently, get out and while ride, in I grabbed a big hurry the to wrong bottle and topped off my clutch fluid reservoir with brake fluid. How much damage might this cause? Should I remove and replace the fluid immediately? Diño Ferrare
Submitted via America Online
A Unless your bike is a KTM or a BMW, its hydraulic clutch uses conventional brake fluid. The owner’s manual and the cap on the clutch master cylinder usually describe the DOT grade of fluid to use, so let that be your guide.
KTM in particular, though, is adamant about the use of mineral clutch fluid in its clutches; brake fluid evidently tends to deteriorate the seals. If you added only a small amount of brake fluid to your clutch reservoir, it should cause no problems; if you added a large amount, you should consider draining the reservoir and refilling it with the correct fluid.
Magic slippers
QI clutches. have a question In your magazine about “slipper” and others, I’ve read enough to have a vague idea of how they work, but it’s unclear to me why they are necessary. I’ve been riding for more than 20 years, currently on a 2006 H-D Sportster and ’04 Kawasaki Concours, and I don’t recall ever having the rear wheel skid or hop because of a downshift. I was taught to rev the engine before letting out the clutch when going down a gear, and that keeps the rear tire in contact with the road. I also wonder if having the clutch slip every time you downshift causes the plates to wear out much faster than they would with a regular clutch. George Simmons
Bridgeport, Connecticut
A Based on the information in your letter, I can only assume that you have never done any roadracing, track days or aggressive twisty-road riding. Because if you had, you surely would have experienced the kind of rear-wheel behavior that slipper clutches are designed to eliminate. Such behavior most often occurs when a rider downshifts while braking so hard that virtually all the weight of bike and rider is transferred onto the front wheel. If the engine is not revved high enough during those downshifts, releasing the clutch delivers abrupt engine braking to the rear wheel, which can make the rear tire—already barely on the ground—hop and chatter and even dance side-to-side. In a race, this can cause the rider to lose precious fractions of a second at each occurrence, and on the road, it can upset both rider and chassis enough to possibly result in a crash. Slipper clutches are therefore designed to release some of the pressure of the clutch springs during trailing throttle, thus allowing the clutch to slip and prevent the sudden introduction of engine braking.
If a bike has a slipper clutch but its owner never rides very aggressively or uses the brakes to their fullest, he or she may never even know it’s there, but it can pay benefits anyway. When the throttle is closed, especially quickly and in the lower gears, the slipper action smoothes the on-off transition enough to eliminate much of the forward jerking that normally might result. This benefits the rider and also helps prevent the passenger from banging into the back of the rider every time the throttle is closed. And no, except on racebikes and some sportbikes ridden with exceptional aggression, a slipper clutch does not significantly shorten clutch-plate life. E2
Got a mechanical or technical problem with your beloved ride? Can’t seem to find workable solutions in your area? Or are you eager to learn about a certain aspect of motorcycle design and technology? Maybe we can help. If you think we can, either: 1) Mail a written inquiry, along with your full name, address and phone number, to Cycle World Service, 1499 Monrovia Ave., Newport Beach, CA 92663; 2) fax it to Paul Dean at 949/631-0651; 3) e-mail it to CW1Dean@aol. com; or 4) log onto www.cycleworld.com, click on the “Contact Us” button, select “CW Service” and enter your question. Don’t write a 10-page essay, but if you’re looking for help in solving a problem, do include enough information to permit a reasonable diagnosis. And please understand that due to the enormous volume of inquiries we receive, we cannot guarantee a reply to every question.
