Service

SERVICE

PAUL DEAN

Planet of the ape-hangers

Q I'd like to install some really tall handlebars on my 2006 Honda VTX1800 because I think they look cool. A couple of my buddies claim those kinds of bars are uncomfortable and make a bike unsafe, but they ride crotch rockets that I think have awful riding positions, so what do they know? don't race my bike on a track or the road; I just ride it around town and sometimes out in the countryside, always at or close to legal speeds. What's your advice?

Daniel Cartwright Rockford, Illinois

A There is no question that high-rise handlebars compromise a rider's ability to control a motorcycle, especially super-tall "ape-hanger" bars. The act of steering a motorcycle involves interaction between the rider's arms and the motorcycle's handgrips, which then have to send those com mands through the handlebars and the steering head down to the front wheel. Obviously, the most direct route offers the best control and feedback; but high handlebars send those messages on an unnecessary detour, requiring the rider’s inputs to be first diverted upward, almost in the opposite direction of the intended action, then make a 90-degree or greater turn downward along a thin tubular pipe. The sheer length of high bars allows them to flex when given substantial input, delaying the delivery of rider commands to the front end and causing the feedback received by the rider to be vague and often tardy.

I don’t know about your region of the country, the Midwest, but here on the West Coast, we’re seeing a resurgence in the popularity of extremely high handlebars. It’s a rare day when we don’t encounter a half-dozen or more bikes-usually but not always Harley-Davidsons-with bars so high that the handgrips are a couple of feet above the rider’s head.

You are correct in your assumption that sportbikes have less-than-comfortable riding positions, but you cannot always equate comfort with control.

I think you would have to agree that all forms of two-wheel racing require the utmost in motorcycle control, yet I have never seen any competitors using high-rise handlebars on their racebikes. If cool means more to you than control, go ahead with your high-bar conversion; otherwise, steer (no pun intended) clear of ape-hangers.

An endless tale

Q l and have the a time 1982 has Kawasaki come to GPz550, replace ain and sprockets, which I had hoped would be a straightforward job. The factory shop manual, however, insists that a continuous chain be used, warning that a master link does not have enough strength and that the standard chain “has been especially designed to withstand the extremely high torque developed by the engine.” The engine develops a mighty 61 horsepower at 9500 rpm and max torque of 35.5 ft.lb. at 8500 rpm. A continuous chain requires removal of the swingarm, which I should be able to do, but it makes this a harder job than I wanted. I was hoping to use aftermarket chains and sprockets, but I am having trouble finding sprockets, and the available chains seem to use master links. I’m inclined to think that either the shop manual is being too conservative or that chains have improved significantly since 1982 and today’s master links are acceptable. I want to replace things for peace of mind but the language of the shop manual makes it sound like my chain at its wear limit is better than a new chain with a master link. What do you suggest?

Joe Twill Glastonbury, Connecticut

A Your assumption that chain technology has advanced over the past 27 years is correct. The performance bikes of the late ’70s and early ’80s elevated levels of power, acceleration and top speed to the point where traditional master links (with push-on retaining clips) had begun to experience increased rates of failure. In an effort to prevent such problems, bike manufacturers began specifying largerthan-usual chains on some motorcycles, as well as chains that contained no master links-“endless” chains, as they were called, that on most bikes required swingarm removal for installation.

Soon thereafter, the chain companies developed the press-on master link that does not require swingarm removal and is still in use today. This link is, in effect, the same as the rest of the links in the chain except that it has not yet been installed. Installation requires a special hand-held riveting tool that’s used first to push a link out of an old chain (not necessary, obviously, on chains with clip-type master links), then to press the sideplate onto the master link of the new chain, and finally to flare out the ends of the master link’s pins to secure the sideplate.

Properly done, this process effectively results in an endless chain, but it does require the use of a chain riveting tool, which can range in price from around $30 to more than $200, depending upon quality. And as far as sprockets for your GPz are concerned, try either Googling “vintage motorcycle sprockets” or going directly to www.sidewindersprockets. com or www.rebelgears.com for custom sprockets, or www.bikebandit.com, where you might find original-equipment replacements.

Another day at the orifice

Q I read your magazine on a regular basis, and I've noticed that some of your road tests describe new or redesigned engines that have fuel-injection nozzles with more orifices than the nozzles on previous models. I’m no fuel-injection wizard and only have a rudimentary knowledge of how these systems work, so I don’t understand the benefit of putting more holes in the same nozzle. In carburetors, richening the fuel mixture is accomplished by installing a jet with a larger orifice. If engine designers want to get more fuel into the combustion chambers with a fuel-injection system, why don’t they just enlarge the existing hole in the nozzles rather than adding holes?

Conrad Bollinger Utica. New York

A Excellent question, Conrad. And the answer is that the engineers usually are not trying to provide a richer fuel mixture; they instead are trying to achieve a more efficient mixture. This is especially necessary to allow modern engines to meet ever-tightening emis sions requirements while also providing the ever-escalating levels of performance that riders expect.

Every molecule of fuel that an engine fails to burn results in three primary consequences: less-than-optimum performance, fuel mileage that falls short of its potential and an increase in unwanted emissions. Injectors that have more orifices of smaller diameter rather than one large orifice vaporize the fuel into tinier particles that mix more readily with the incoming air and thus are more likely to bum than larger particles. The more fuel that is burned with each gulp of the intake, the more power the engine can make with that quantity of fuel while producing fewer emissions.

Engines with injectors located in the intake ports (which describes most EFI systems) also tend not to be entirely fuelefficient because the injectors are so close to the combustion chambers that there isn’t adequate time for the fuel to completely vaporize, especially at higher rpm. This is one reason so many highperformance engines are now using secondary injectors above the mouths of the intake velocity stacks. The longer path from injector to combustion chamber allows more time for the fuel to vaporize, and the “showerhead” design of those upper nozzles also helps achieve more-complete vaporization.

Dyno numbers game

Q How is torque calculated on a dyno, and how do the manufac turers get their torque figures? Are the torque numbers taken at the rear wheel or are they calculated based on what is measured at the crankshaft, taking into account tire diameter, gear ratio, me chanical losses, etc.? If, for example, a bike makes 100 ft.-lb. of torque at the rear wheel, and the torque reading was made with a transmission ratio of 1:1 and a fi nal-drive ratio of 3:1(14/42 on my bike), not taking into account mechanical losses, that means the engine is only making 33.3 ft.-lb. of torque at the crank. This doesn't compute in my mind. I have asked a couple of dyno operators in my area aboul this and they couldn't give me an answer, so now I am asking the real experts. How is it done?

dill 4SlU1l~ LIIC LCd! CApCILS. UIUW Rod Havens 3urnaby, British Columbia, Canada

A Dynamometers measure torque by either of two means-one very simple and direct, the other a little more complicated. The direct type is a brake dynamometer on which the engine spins a special braking device connected directly to the crankshaft or the countershaft, or via a drum turned by the bike’s rear wheel. Depending upon its design, the brake uses either water, oil or electrical current to provide a variable resistance to rotation. The brake also is attached to a load cell that measures the resistance in terms of torque at any or all engine rpm. While those measurements are taking place, the dyno’s computer calculates the horsepower by using the standard formula for that purpose (hp = torque x rpm ^ 5252).

The other type of dynamometer-which actually is an accelerometer-measures horsepower, and the dyno’s computer then mathematically converts that number into torque. On this type, the bike’s rear wheel spins a heavy drum, starting at a low rpm and accelerating up to redline, while the dyno reads drum rpm many times a second. The dyno’s computer knows how much the drum weighs and how long it took for the drum to be spun from any given rpm to any other rpm; so, using that data, it calculates how much “work” was accomplished at any point in terms of horsepower (which is a form of work). The computer then converts that horsepower to torque using a slightly different formula (torque = horsepower x 5252 + rpm).

With very rare exception, manufacturers take their torque readings directly at the crankshaft. They may also take readings at the countershaft or the rear wheel to help them determine driveline efficiency, but their claimed horsepower numbers-which are not always published-were taken at the crank. This yields the highest numbers, since they do not reflect the frictional losses of the primary drive, the transmission, the final drive or any other aspect of the drivetrain.

And yes, if a motorcycle develops 100 hp at the rear wheel and the overall gear ratio is 3:1, the engine is indeed producing 33.3 hp-not counting frictional losses between crank and rear wheel. But when rear-wheel dynos measure horsepower, the dyno’s computer knows the exact crankshaft-to-rear-wheel ratio (by comparing drum rpm to engine rpm as detected by an electronic tachometer that connects to the bike’s ignition and is wired to the dyno). The computer then uses that ratio to convert the power measured at the rear wheel into power at the crankshaft.

You didn’t tell me what kind of motorcycle you own, so I can’t offer much of a reply about the horsepower number you supplied-other than to believe that although it was measured at the rear wheel, the dynamometer used the aforementioned crankshaft-to-rear-wheel ratio to determine the horsepower at the crank, n

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) Mall 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 CW1 Dean@aol.com; or 4) log onto www.cycle world.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.