Service

SERVICE

Rubber chickens

I currently own a Honda RC51 and previously had a Honda Super Hawk, and I’ve heard some people say that any rear tire wider than a 180 is not needed. I find this a little strange, because the “chicken strips” on my RC51, which has a 190-section rear tire, are a lot smaller than the ones that were on my Super Hawk’s 180 rear tire. So, why am I using more of the rubber on the RC’s wider tire than I did on the Super Hawk’s narrower tire? Of course, these bikes handle totally differently, and by their very nature are completely different machines, but what gives? David Cruise Alachua, Florida

I think you’ve largely answered the question yourself, David: Those two bikes are sufficiently dissimilar that they won’t necessarily exhibit the same degree of tire-tread usage, even when both are cornered with equal levels of aggression. Not only are their tire sizes different, so are their rim widths-5.5 inches on the Super Hawk and 6 inches on the RC51. So, while the RC51 s tire is 10mm wider, it’s mounted on a rim that is 12.5mm wider, which spreads the beads 2.5mm farther apart in proportion to tire width than its counterpart on the Super Hawk. That would marginally increase the radius of the 190 tire ’s tread surface compared to that of the 180, making it easier to get a greater percentage of the tread on the ground at any given lean angle.

Furthermore, unless the two tires in question are the same models from the same manufacturer, the radius of the tread surface may not be exactly the same on both, regardless of rim width. That alone could account for the differences in your two Hondas’ “chicken strips ’’ (slang for the outside edges of a tire’s tread surface that have never touched the ground).

Besides, isn’t it reasonable to assume that you have improved as a rider since buying your RC51, either as the result of riding a more-capable sportbike or by logging more seat time-or both? If so, you merely may be leaning your RC51 over farther more comfortably than you did your Super Hawk.

Truth is, on the street, the vast major-

ity of riders probably do not need a tire wider than a 180. Roadracers, accomplished track-day participants and a small number of very skilled riders who regularly play-race on familiar backroads might make good use of a wider tire. Otherwise, the normal constraints of riding on the road prevent most motorcyclists from making full use of even a 180 tire. Your experience is a pretty good example: Even on a more-sophisticated motorcycle with a wider rear tire, you ’re still left with unused tread area. In the context of street riding, though, I wouldn’t refer to them as “chicken strips I’d call them evidence of a sensible rider.

Twins is Twins

I am looking to purchase a new bike and have asked various people to explain the difference between inline-Twins and VTwins. I sometimes get the same silly answer of torque and horsepower, but I know I can change both of those with aftermarket parts. I would like a more in-depth answer involving things like repairs, performance and maintenance costs-anything that could influence a person’s decision to buy one or the other. Any help is greatly appreciated. Sgt. Donald Roeder United States Marine Corps Posted on America Online

Actually, when it comes to torque and horsepower, there aren 't necessarily any significant differences between inlineand V-Twins, so long as all other factors are the same-displacement, bore and stroke, compression ratio, cam specifications, carb or throttle-body diameter, etc. Those are the factors that affect an engine’s performance, and in that regard, two cylinders don’t much care if they are arranged in a Vee or parallel with one another. Thus, just about all performance differences are dictated by the tuning specs chosen by each engine ’s manufacturer rather than by cylinder arrangement. A V-Twin certainly won’t feel or sound like an inline-Twin, but the power outputs of the two could very easily be comparable.

Repair and maintenance costs can be an entirely different matter. Some V-type motors tend to be more time-consuming to disassemble and reassemble, since they require the removal of two separate cylinders and heads rather than just one. With overhead-cam V-Twins, rebuilds also involve the need to deal with and time twice as many cams and cam drives. Ducati VTwins have desmodromic valve gear that can render valve adjustments a time-consuming process; conversely, many other V-Twins have hydraulic valvetrain devices that eliminate altogether the need for valve adjustments, whereas most inlineTwins do not.

In the end, the design details of any given engine have more effect on its repairability and maintainability than the orientation of its cylinders. I don’t know of any V-Twin or inline-Twin that presents sufficient maintenance and repair problems to make ownership prohibitive, just as I don’t know of one that, on this same basis, makes its ownership an especially shrewd move.

So, the answer to your question depends upon which inline-Twins and VTwins you are considering. In the end, you have to ask yourself if you ’re willing to live with an easy-to-maintain motorcycle you don’t like as much as one that is slightly less maintenance-friendly.

Gimme a rake

In various magazines, including yours, I sometimes see a motorcycle’s steering geometry described in terms of “rake and trail,” and other times it’s mentioned as “steering-head angle and trail.” I believe I know what trail is, because you explained it in Service a couple of years ago, but I’m a bit confused about this rake and headangle thing. Any chance of you explaining the difference between the two? Marc Donatelli Binghamton, New York

Those terms are often used as though they both describe the same thing, which has prompted many people throughout the motorcycle industry to consider them interchangeable. Technically, though, they are not one and the same. Steering-head angle is a self-explanatory term, since it refers to the angle of the centerline that passes through the steering head and continues on down to the ground. That angle is usually stated in degrees from vertical-a 24-degree steering-head angle, for instance, is tilted 24 degrees rearward from a vertical plane. Rake, on the other hand, is intended as a measure of the angle of the fork tubes, which may or may not be mounted at the same angle as the steering head.

On the vast majority of motorcycles, the fork tubes are at precisely the same angle as the steering head, so either term would apply to the head angle. But on some motorcycles, the fork tubes are mounted at a slightly different angle than the steering head, usually to give the steering a certain feel or improve the handling characteristics. This, in fact, is how some chopper and custom builders “cheat” the front-end geo-

metry for more-acceptable steering behavior when using an extended fork: They use triple-clamps that attach the tubes at a greater angle than the steering head, thereby reducing front-wheel trail to a more reasonable level. That helps lessen the amount of front-end “flop ” that is characteristic of kicked-out front ends. Obviously, then, on any bike that has its fork mounted at a different angle than its steering head, the two terms are not interchangeable.

The Grommet Chronicles

I’ve got a 1990 Harley-Davidson FXR that leaks/seeps oil out of the inner primary through the rubber plug on the alternator wire. How can I stop it? Dan Blackham Ellwood City, Pennsylvania

Pretty easily, actually. This is a relatively common problem with H-D Evolution Big Twins (1984-2000), brought about when long-term exposure to engine heat causes hardening of the rubber grommet that is molded onto the alternator wire. Once it hardens, the grommet can lose enough of its elasticity to permit small amounts of primary oil to seep past. On the Twin Cam successors to the Evo engines, the grommet has a different shape and taller sealing ribs around its circumference, both of which help it provide a better seal, even when it hardens over time.

To cure the leak, pull the primary cover, remove the alternator stator and give both the rubber grommet and the alternator-wire hole in the primary case a thorough cleaning with contact cleaner or a similar solvent. Then apply a light coating of silicone sealer around the entire circumference of the grommet and slip it back into place. Clean off any excess sealer before reattaching the primary cover, and when the sealer dries, the leak should be stopped in its tracks.

You da main!

I have a 2001 Kawasaki ZRX1200 that I bought used with around 2000 miles on the clock. The previous owner installed a Dynojet carb kit and a Muzzy slip-on silencer, and I’ve installed a K&N air filter and a Ted’s spark-advancer plate. The bike runs very well from idle to redline but does not have the roll-on performance from 60 or 70 mph that I believe it should. In fact, in a 65-mph roll-on, the bike will pull harder if I roll off the throttle a bit. I have the needles on their next-to-richest notch and the plugs look fine. If I drop down a gear and let the revs build, she flies, but that great ZRX roll-on is lacking a bit. Ron Vance Philadelphia, Pennsylvania

Sounds like a classic case of the main jets in the carbs being too large. The main jets come into play only when the throttle slides are more than three-quarters open; when they ’re between about one-third and three-quarters open, the needles and their mating needle jets control the mixture. If the main jets are too large, the mixture at full throttle will be too rich and the engine won’t pull as strongly as it should when the twistgrip is turned wide-open. This would be especially noticeable when accelerating from moderate rpm in top gear, which makes the engine work its hardest to accelerate the motorcycle. But when you roll off the throttle slightly, the slides drop

far enough that the needles then meter the fuel; the needle settings you have chosen apparently are much closer to ideal, so the engine pulls harder with less throttle.

These symptoms indicate that the main jets are too big. The obvious solution is to reduce the size of the mains, one increment at a time, until you feel the roll-on power returning. And always, after every and any jetting change, take a good plug reading to ensure that you haven’t made the mixture too lean or too rich.

Gravity check

I recently purchased a 1993 Honda Gold Wing with 20,000 miles on it. I am happy with the bike overall, but there is one thing about it that concerns me: When I start it after it has been sitting for a while, it gives off a puff of smoke from the exhaust. I don’t notice this same symptom any other time. My Honda dealer told me this is a common occurrence because of the layout of the engine. Do you agree? If so, please explain. Ron Krueger Howards Grove, Wisconsin

Your dealer is correct; the horizontally opposed layout of your Gold Wing’s cylinders is to blame. On an engine with cylinders that are vertical or have any upward > inclination whatsoever, oil that has accumulated on the cylinder walls below the piston rings during normal running simply drains back into the crankcase when the engine is turned off. But with horizontal cylinders, that oil tends to drain down to the lowest part of each cylinder wall and collect there; and if the bike is parked on its sidestand, which tilts the entire engine to the left, any residual oil in the right-side cylinders will drain into the crankcase but the oil in the left cylinders will run downhill until it comes into contact with the piston rings. If the rings are worn, or if the end gap of a couple of the rings just happens to be at or near the lowest part of the piston, the oil will gradually seep past and accumulate in the combustion chamber. Then, when the engine is fired, it will smoke briefly until it burns off that accumulated oil.

Recall Roster

NHTSA Recall No. 04V028 BMW R-series and K-series models Model years: 2001-2004 Dates of Manufacture: May ’00-Dec. ’03 Number of units involved: 39,000 Problem: On certain motorcycles, the 0ring in the fuel-line quick-disconnect coupling could become damaged and lead to a fuel leak. There also is a problem involving the crimp-type hose clamps, which also can result in a fuel leak. Fuel leakage in the presence of an ignition source could cause a fire. Remedy: Dealers will inspect and, if necessary, adjust all crimp-type hose clamps and fuel line quick-disconnect couplings.

If any leaks are detected, the quick-disconnect 0-ring or couplings will be replaced. Owners who do not receive these free remedies within a reasonable time should contact BMW at 800/831 -1117.

NHTSA Recall No. 04V008 2003-04 Kawasaki Vulcan 1500 Classic, 2003-04 Vulcan 800 Classic, 2004 Vulcan 800

Number of units involved: 2082 Problem: On certain motorcycles, the accelerator-pump diaphragms may be damaged due to excessive assembly clamping pressure, which can allow fuel to leak from the pump’s actuating-rod area. Fuel leakage in the presence of an ignition source could result in a fire. Remedy: Dealers will replace the accelerator-pump diaphragm. Owners who do not receive this free remedy within a reasonable time should contact Kawasaki at 949/770-0400.

NHTSA Recall No. 04V023 2003-04 Kawasaki Vulcan 1500,

2003 Vulcan 1600 Number of units involved: 6958 Dates of manufacture: June ’02-Feb. ’03 Problem: On certain motorcycles, high oil pressure upon cold start-up can deform the oil-filter cartridge, allowing oil to leak past the 0-ring, possibly causing a loss of traction and a crash.

Remedy: Dealers will replace the oil filter. Owners who do not receive this free remedy within a reasonable time should contact Kawasaki at 949/770-0400.

This is a common occurrence on engines that have transverse horizontal cylinders. These include not only Gold Wing Fours and Sixes but also BMW’s Boxer Twins and inline K-model engines, the latter of which aim all three or four of their cylinders downhill when the bikes are parked on their sidestands.

If your Gold Wing runs nicely and only emits a small, brief wisp of smoke when first started, don’t lose any sleep over it; the amount of oil involved is too trivial to be of concern. But if even that little puff of smoke bothers you, try parking the bike on its centerstand. That will keep the cylinders horizontal and prevent gravity from having its way with any residual oil on the cylinder walls. If the smoking is excessive and the engine consumes oil at an excessive rate, however, a top-end rebuild may be in order.

FEEDBACK LOOP

In the May issue, a reader tore into you for criticizing the “Beach Bars” on the Harley-Davidson Road King Custom (“No-day-at-the-Beach Bar”). I thought you should know that I just put my name on the list at my local Harley dealer for a 2005 Road King Custom, but before that bike ever rolls out of the showroom, I’m going to have a custom exhaust installed and get rid of those damned beach bars. Even the dealer agreed with me. He said that a lot of people who buy the Custom end up replacing the bars. I also intend to replace the seat, but that will be a little farther down the road. Derick Dallas Posted on America Online

Thank you for that tidbit of information, Derick. I’m pleased to learn of a Harley dealer who not only agrees with our assessment of the Custom’s handlebar bend but also acknowledges his customers’ dissatisfaction with it. Hey, we don’t make this stuff up, you know?

Whole lot o’ shakin’

My Harley-Davidson, an early ’91 FXRS with only 15,000 miles, has developed a strange vibration that’s kind of like a grinding/shuddering. In each gear, it begins at about 2200 rpm (15 mph in first, 22 mph in second, 30 mph in third, etc.) and is gone by 2700 rpm. It’s very obvious at 25 mph in second gear but not there at 25 mph in third gear. I’ve checked the engine mounts and stabilizer links, and the frame, wheels and tires all appear in good condition. Everything else seems completely normal, and if I keep the rpm above 3000, there is no noticeable problem. Terry Lundgren Charleston, Illinois

TECHTIPS

When reinstalling a front wheel, many mechanics-either pros or those of the shadetree variety-don’t take one important step that can allow the front suspension to function at least as smoothly afterward as it did before. With most front-axle attachment systems, one end of the axle threads either directly into one of the fork legs or into a threaded sleeve nut in one of the legs, while the opposite end of the axle is smooth and secured by pinch bolts that clamp it to the leg.

To ensure that the fork tubes will travel up and down smoothly in their stanchions after reassembly, first thread the axle into place and fully tighten it, along with any pinch bolts on the threaded end; then, with the pinch bolts at the smooth end of the axle still loose, butt the wheel against something solid, like a wall, and repeatedly pump the front end up and down as far and fast as you can by alternately pushing and lifting on the handlebar. This automatically aligns the tubes and stanchions for the smoothest operation. Pump the fork up and down at least a half-dozen times, and don’t use the front brake when doing so or the action of the calipers may prevent the legs from centering themselves. Once you’ve completed this procedure, tighten the pinch bolts and the job is finished.

Paul Dean

There are three probable causes for this rpm-sensitive vibration: a loose primary chain; a loose nut on the compensator sprocket; and the deterioration of the rubber on the engine s stabilizer links.

With just 15,000 miles on the engine, the primary chain should not be worn out; but if it never has been adjusted, it could be loose enough to cause the shuddering and grinding you describe. Remove the primary cover and check the chain’s freeplay on the top run about halfway between the engine sprocket and the clutch. It should have no more than 7/8-inch of up-and-down play. If it has more than that, adjust it to between Vsand 7/8-inch by raising the adjuster shoe below the bottom run of the chain. While you’re poking around in the primary case, check the torque on the compensator-sprocket nut on the end of the crankshaft. It should be torqued to between 80 and 100 lb.-ft.

Although you said you “checked” the engine stabilizer links, you might want to inspect them very closely. The links have rubber bushings on their ends, and if the rubber has hardened or deteriorated (not unusual on a 13-year-old motorcycle), the reduction in their ability to isolate the engine’s shaking can allow some weird vibrations to travel throughout the motorcycle, more so in some rpm ranges than in others. E3

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 949/6310651; 3) e-mail it to CW1Dean@aol.com, or 4) log onto www.cycleworld.com, click on the “Letters to the Editor” button 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.