Service
SERVICE
PAUL DEAN
Economics of Inflation
Q When I picked up my Suzuki 1200 Bandit after a recent service visit, the dealer literally yelled at me for allowing my tires to become underinflated and lectured me about what could happen as a result. Okay, my bad for not checking the pressures as often as I should. I understand what he said about how I could lose control if the pressures were too low, but I didn't quite get it when he told me that the tires could fail prematurely, too. They weren't flat or anything, just a few pounds below the recommended pressures. Was he correct or just trying to scare me into paying more attention to my tires? Dave Caldwell Baltimore, Maryland
A Both, actually. First, you need to understand that the two great est enemies of tire life are speed and weight. As a tire rolls down the road, it is constantly flexing at or near the
contact patch; and because the contact patch continually moves around the tire's circumference as the wheel rotates, the flexing does not occur in one spot but rather over the entire carcass. That flex ing generates heat, and if the tempera tures reach excessive levels, the structure of the tire can begin to deteriorate. The heat tends to cook the oils out of the rubber, resulting in blistering of the tread, and it also can make the carcass delaminate, which could eventually lead to sudden catastrophic tire failure.
Tc~~icmre. The faster the wheel rotates, the more of ten any given part of the tire will flex over any period of time, resulting in greater heat buildup. Plus, if you increase the weight that the tire is supporting, the tire will flex to a greater degree, also creating more heat over a given period. If you increase both the speed and the weight beyond the tire manufacturer's ratings, problems are likely to arise.
Riding with underinflated tires does not significantly raise the wheel's rpm
at any given speed, but it does cause the tire to flex excessively, greatly increasing the likelihood of heat-related problems. Once the level of underinflation reaches a certain point (which varies for each dif ferent bike/tire combination), the tire is more prone to wear faster and fail sooner than it would from just being overloaded and/or run at very high speeds.
Sounds to me like your dealer is a responsible person concerned about the well-being of his customers. You should heed his advice.
Hot wheels, cool fan
Q I thoroughly enjoyed Paul Dean's sidebar article ("Hot Wheels") that was part of the 2007 Harley-Da vidson Fat Boy road test in the January issue. The irony is that H-D already may have had the solution to the heat prob lem as recently as the 2005 model year, then mysteriously deleted it from their accessories lineup. I'm referring to the Dyna Cooling Fan (part #91552-OOA).
This fan, which (in a 1930’s s^rt of way) resembles the right-side air c .ner, is affixed on the left side of the engine, right in the vee between the cylinders, requiring relocation and replacement of the stock horn. It is thermostatically controlled to come on during those long, hot El Paso parades when the asphalt soars to 212 degrees. If it fits the Dynas, surely it could be made to work on all Big Twins. Hey, cut a *&%$!#@ hole in the fairing if the E-Glides need more air to accommodate it. I wrote Harley last May to inquire as to the parade fan’s disappearance, only to get a vague reply that they don’t discuss future products. Maybe you can fare better.
David Reid Chenault Mount Sterling, Kentucky
A Actually, Harley has not stopped selling those fan kits; the company only discontinued the version intended for the Dyna series. The fan is still available to fit 1997 and later fuel-injected FL touring models (part #91550-00C in chrome for $380 or #91551-00D in black for $350). Anyone with even a scintilla of creativity could adapt one of those to other H-Ds.
I didn’t mention the fan in the “Hot Wheels” sidebar because its installation would not solve the problem of riders and passengers being assaulted by intense heat radiated from the engine. The purpose of the fan is to keep the engine from overheating when operating in parade mode on hot days, not to keep the bike’s occupants cool.
To maintain acceptable temperatures, air-cooled engines rely on the passage of air through the fins on the cylinders and heads, and that doesn’t happen, obviously, when the bike is stationary or moving at a very slow pace. The H-D fan is designed to switch on when the cylinder temperatures get too high, and it moves the air through the fins when the fins are in effect unable to move through the air. As a consequence, the fan would further elevate the level of discomfort felt by the rider and passenger by directing a greater volume of hot air between the cylinders and out onto their right legs. So, while the engine might appreciate the fan, the bike’s occupants f|; would not.
Exhaustive guesswork
Q This may be a stupid question or it just may be genius; you decide. Does it help or hurt the performance of a motorcycle to "punch out" the exhaust? I have a 2001 KTM Duke that has two very restrictive cans. I am capable of tearing them apart and reworking them to have a 2-inch-diameter perforated tube surrounded by baffling for only about $100, or I can purchase aftermarket muf flers for $500 to $1000. If it is beneficial to do this modification myself, should I fabricate the first half of the perforations to direct air into the baffling and the second half to direct it out? J.J. Helm St. Cloud, Minnesota
A J.J., I have absolutely no idea how you should fab your mufflers or what the performance outcome might be. And unless you can find someone who has performed the very same modifica tions on the very same model of motor cycle, neither does anyone else. I can guarantee you that the exhaust note will be louder than stock, but other than that, you're riding full-throttle into unknown territory.
What you are attempting is purely an R&D experiment. This is what people who build exhaust ... ^
systems for a living rou( tinely do, but they have V'C years of experience and a vast knowledge of the kinds of things that work and don’t work. They usually start with a basic design they think is in the ballpark and then finetune it step by step. Sometimes, even the tiniest dimensional differences in one part of an exhaust system or another can make a huge difference in performance.
But in the end, they never know for certain how modified exhaust pieces will work until they install them and test the results. Even then, they frequently end up scrapping a new design after the dynamometer proves that it doesn’t do anything positive for performance.
If I had to predict the likely outcome of your project, I’d say there’s at least a fair chance your Duke could gain a horse or so on top end but is also likely to lose more than a couple of foot-pounds of torque in the midrange. Whether or not such a trade-off would be worthwhile is up to you. But then, you have to take my speculation with a grain of salt because, just like you, all I’m doing here is taking a WAG (wild-ass guess).
Urine big trouble
QI can’t stand it anymore. Just one look at the Triumph Tiger 1050 on the front cover of your November issue makes me ask this question: Can somebody please explain why so many motorcycle manufacturers are using cheesy-looking, cheap plastic cylindrical brake-fluid reservoirs? Is there a performance advantage to this style of reservoir or is it just cheaper to manufacture than the nicely styled aluminum brake reservoirs of yore. I would think an aluminum reservoir would be a lot more rugged and unobtrusive. The plastic reservoir looks like a urine-sample container on the Triumph Tiger and totally ruins the aesthetics of the bike.
John T. Gavula Posted on www.cycleworld.com
A As Í recall, the origins of this particular style of plastic reservoir go back to racebikes and
racers of the 1980s.
In their neverending quest for lightness, simplicity and easier postcrash repairs, race tuners and factory R&D departments of that era began equipping competition bikes with small, remotely mounted plastic reservoirs.
The fluid capacity only needed to be sufficient to compensate for brake-pad wear over the course of a single race, not for the total life of the pads over many thousands of street miles. Plus, moving the fluid supply slightly inboard on the handlebar, away from the master-cylinder piston, gave the reservoir greater protection from damage in the event of a crash. Separating the reservoir and piston also allowed easier replacement if either got damaged, or if the need arose to use a master cylinder with a larger or smaller piston diameter.
I can’t absolutely verify this, but I believe that over time, the bike manufacturers began using these remote reservoirs on select other models-besides racebikes and hard-core sportbikes-because of cost. These designs are less expensive, and eliminating the need to have integral master-cylinder reservoirs on certain models opens up some mix-and-match possibilities that allow the manufacturers to use a lot of the same components on a number of different bikes.
Í, too, dislike the appearance of these ungainly reservoirs on anything but competition bikes. And they’re not even original; when hydraulic disc brakes first appeared on production bikes starting with the original CB750 in 1969, round translucent plastic master-cylinder reservoirs with screw-off tops were practically universal. The only difference is that they were integral with the master cyinder rather than remote as they are now.
Sticker shock
QI am the happy owner of a 2006 Victory Hammer and have removed most of the “we must protect you” stickers located all around the bike. Do you know of a safe way of removing the fuel warning label from my beautiful blue gas tank? I’m having nightmares of gouged and dulled paint. Dave Kling Posted on www.cycleworld.com
A Not a problem. First, use a hair dryer to soften up the glue on the sticker. As soon as it gets pliable enough, you should be able to peel the sticker off in one piece without using a knife or any kind of scraper. You might have to use a fingernail to get it started on a corner, but unless your real name is Freddy Krueger, that won’t scratch the clear coat. If the sticker leaves behind a little adhesive, remove it by spraying some WD-40 on a clean, soft cloth and rubbing gently over the affected area until all the residue is gone. Most hardware and auto-parts stores sell a product called Goo Gone that’s formulated to remove adhesive left after the removal of stickers and decals, but for most such situations, WD-40 works just fine. A coat of wax after you’re finished will have that part of the tank looking just as perfect as the rest. □
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 “Contact Us” button, select “CW Service” and enter your question. Don’t write a 10page 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.
