Service
SERVICE
Paul Dean
It's April, fool
Mr. Dean, I wish to protest the demeaning manner in which you continually characterize a very fine human being, Mr. Bubba of Bubba’s Moorsycle Shop. In many past issues of Cycle World, the illustrations in your Service column have shamelessly portrayed Bubba as a mindless, lowbrow buffoon barely able to provide his customers with inferior repair work. You and Mr. Cademartori might be shocked to learn that not only is Bubba a highly skilled craftsman listed in the prestigious “Who’s Who of Lawnmower Mechanics,” he also is a pillar of his community and a patron of the arts, having raised large sums of money for charity with his annual “Art & the Moorsycle” bacchanal. This is a true gentleman held in the highest regard by People Who Matter, a select group that does not include you among its members. Mr. Con D. Scending
New York, New York
My most humble apologies, Con. Only recently did I learn of Bubba’s high standing amongst the hoity-toity of the cultural movers and shakers. I have grossly misjudged him in the past, for he clearly is a man of high breeding and impeccable taste. Matter of fact, I understand that Queen Elizabeth intends to recognize his exceptional work with outdated British motorbikes by knighting him later this year.
What a man-bon vivant, raconteur, gourmet chef, art critic, trend-setter extraordinaire. Now soon to be “Sir” Bubba. Gosh, who ’da thunk it?
It's that size thing again
I have a question that’s been bugging me for a while, but no one has ever been able to give me a reasonable answer. I own two bikes, a stock 2001 Harley-Davidson Road King that I take on casual rides and short trips with my wife, and an equally stock 2002 Suzuki Hayabusa that I ride alone to scare the hell out of myself. The Harley always gets better fuel mileage, no matter if I ride two-up or solo, even though it has a bigger engine, 1450cc as opposed to the Suzuki’s 1299cc. I’m not talking about wide-open running; if I ride both at about the same speeds over the same roads and discipline myself to accelerate about the same on the Suzuki as I do on the Harley, I still get much better mileage on the bigger bike. Why is that?
Don Haslelt Posted on www.cycleworld.com
When fuel is burned in an engine, not all of the heat of combustion is transformed into energy that drives the piston downward; some of it is lost in heating the surfaces inside the cylinders. The affected surfaces are those directly exposed to the heat of combustion-the piston crowns, the combustion chambers (including the valves) and the cylinder walls. The more surface area there is to heat, the more energy that is lost, generally reflected in the rate of fuel consumption. The more cylinders an engine has for any given displacement, the more area that is exposed to the heat of combustion. Engineers refer to this relationship as the surface-area-to-volume ratio. So, even though the 1299cc four-cylinder Hayabusa has 10 percent less displacement than the 1450cc twin-cylinder Road King, it works out to have about 15 percent more surface area.
But there ’s more. Obviously, when both bikes are run at full throttle, the Hayabusa burns more fuel than the Road King, since it makes about 2V2 times more peak power than the Harley. When both bikes are cruising at the same road speed, however, both are making approximately the same horsepower; the difference is that the Hayabusa ’s four-cylinder engine is turning much higher rpm than the Harley ’s motor. Each of the Suzuki ’s combustion events are smaller, of course, but it produces more of them more often, and that leads to higher fuel consumption. There are a few other contributing factors, as well, but these are the most consequential. >
Really wanna wheelie?
I have a ’93 Suzuki GSX-R750 that I want to gear down for two reasons: 1) To get faster acceleration at the start, and 2) to wheelie easier. The bike comes up okay in first gear with the clutch, but after that, no way. The gearing now is 15/43, and the bike has a Yoshimura slip-on, a K&N air filter and a Stage I jet kit. It runs very strong, but when I see videos of guys snapping their bikes up on the rear wheel at all kinds of speeds, I want to make my GSXR easier to wheelie. Can you shed a little light on the subject? Raymond Friedland Southbridge, Massachusetts
FEEDBACK LOOP
I beg to differ with your opinion that Yamaha invented the “trend of canting the cylinders of inline-Fours forward” (“Cylinder inclinations,” February, 2004). The 1979 Honda CBX was clearly the first inline Multi with forward-slanted cylinders. Okay, it wasn’t a Four, but the Honda dohe Fours of contemporary vintage—/.e., the 79 750F, ’80-82 900F and ’83 1100F-featured a very similar, although not as pronounced, inclination. Sorry, but in my book, that prize belongs to Big Red.
E.M. Simon North Royalton, Ohio
Paul Dean may be a bit too young to remember-or maybe I just have too much focus on the past-but in regard to his claims about cylinder inclination, he may want to go back and look at the Triumph and BSA Triples of the early 70s. The Triumph’s cylinders were straight-up but the BSA’s leaned forward, and all of the factory Triumph/BSA roadracers used the inclined cylinders, no matter if the bike was red or blue in color. Randall Davis Irvine, California
Thanks for the input, guys, but you both have overlooked six key words in my response. The relevant sentence in my statement, in its entirety, was, “With its Genesis engines in the 1980s, Yamaha began the current trend of canting the cylinders of inline-Fours forward in order to permit straighter intake tracts.” The all-important words here are “current” and “to permit straighter intake tracts.” Yes, the late’60s BSA Triple had inclined cylinders, as did the ’79 CBX Six and all the other Hondas pointed out by Mr. Simon. But it was Yamaha who began to cant the cylinders dramatically forward for the express purpose of allowing straighter intake tracts, using semi-downdraft carburetors and airboxes tucked up into the underside of the gas tank.
By the way, I wish I were too young to remember those BSA and Triumph Triples. But at 62,1 not only remember them, I used to sell them and ride them.
This might not be what you want to hear, but the biggest problem isn 't with your GSX-R; it’s with your technique. Although the guys you see in those videos usually are on bikes that are at least slightly hopped-up, that ’s not the only reason they can snap the front end into the air at fairly high speed and ride off into the sunset on one wheel; their technique and confidence are what allow them to do it. I’ve never seen or ridden your bike, but I flat guarantee you that one of those stunt riders would not be restricted to first-gearonly wheelies on it.
Changing the gearing isn’t the answer, either. If you were to drop the gearing quite radical ly-say, from 15/43 to 14/45, a change of 12 percent-second gear would still be taller than first gear is right now, third taller than second, and so on. Which means that while you might then be able to yank the front wheel up in second gear, third gear and beyond would still be off-limits for wheelies so long as you used your current technique.
If you really want to improve your wheelies, get some personal instruction from a pro. You might consider contacting Keith Code’s On One Wheel school (323/224-2739; www.ononewheel.com): by the time you read this, he may have expanded his one-day wheelie-training classes to a location near you.
An idle threat
I have a 1990 Kawasaki 250 Ninja that will not idle at all. At first, I thought the carbs were the problem so I had them fully cleaned, but that didn’t work. So I bought brand-new carbs, and that didn’t work, either. I messed with the pilot jets and mixture screws but nothing has helped. If I adjust the idle speed up to about 3000 rpm, the engine will idle, and it runs like a bat out of hell from that rpm upward. I think that the valves need adjusting. What do you think? Will Vance Stamping Ground, Kentucky
I think you are correct: The valves need to be adjusted. More than likely, just one of the Ninja 250’s eight valves has tightened up to the point where it is not fully closing. As a result, there isn’t enough intake vacuum in that one cylinder to draw in sufficient fuel-air mixture; and much of what does get > into the cylinder leaks past that same valve during the compression stroke. At higher revs, the intake and compression events take place so quickly and the incoming charge is moving so rapidly that the engine seems to run fairly normally; but at idling speeds, things happen slowly enough for the loss of intake and compression to effectively kill that cylinder’s production, eliminating one-half of the 250cc Twin ’s power output. Working alone, the other cylinder can’t compensate for the drag of overcoming the dead cylinder’s valve-spring tension and compression resistance. Have the valves adjusted by a hwwledgeable shop or mechanic—and do so as soon as possible, before the affected valve gets damaged to the point where it has to be replaced.
Bad sensory input
I’m having a sparkplug problem with my Suzuki, a 2001 GSX-R1000 that has 8700 miles on the odometer. When the sparkplugs are new, the engine fires up almost immediately, but after about 200 miles, it begins getting hard to start. By 300 miles, it has to crank for 5 or 6 seconds before starting, and sometimes it doesn’t run on all four cylinders for a few seconds once it starts. If I don’t change the plugs soon thereafter, it may not start at all. After a plug change, all is well again for another 200 miles or so.
On several occasions, I’ve checked the plugs after they’ve been in the bike for a short time, maybe 25 or 30 miles, and they have a slightly black, sooty appearance. By the time I have to replace them, they’re very black and sooty. I’ve tried the next higher heat range, but that hasn’t helped. Once the engine is started, the bike seems to run just fine, although it has so much power at all rpm that it’s hard to tell if it’s off a little bit. If you have any suggestions, I would really welcome them. John David Hastings
Recall Roster
NHTSA Recall NO.03V483 BMW R1100/R1150 Model year: 2003 Dates of manufacture: Dec. ’02-Aug. ’03 Number of units involved: 7000 Problem: On models with twin-spark ignition, the electrical wiring for the oxygen sensor and the ignition lead for the rightside secondary sparkplug have a parallel routing over part of their installation path. The proximity of these cables may allow the signal from the ignition lead to interfere with the signal from the oxygen sensor wiring. As a result, engine hesitation or misfiring could occur, which could result in a crash. Remedy: Dealers will re-route the wiring to the oxygen sensor. Owners who do not receive the free remedy within a reasonable time should contact BMW at 800/831-1117.
Posted on America Online
It ’s my guess that your Gixxer has a faulty sensor in the fuel-injection system, causing the engine to run too rich. More than likely, the culprit is either the engine-temperature sensor or the MAP (manifold absolute pressure) sensor. During normal, fully-warmed engine operation, the engine-temp sensor may be telling the ECU (engine control unit) that the motor is still cold, and so the ECUfeeds the injectors more fuel to compensate, just as it does during normal cold running. Same goes for the MAP sensor, which could be telling the ECU that the manifold pressure is higher than it actually is, which will prompt the ECU to deliver more fuel. Either way, the engine receives a slightlytoo-rich mixture that fouls the sparkplugs in a short period of running time.
A capable Suzuki dealer should be able to diagnose this problem-the operative word being “capable.” Hopefully, there’s a Suzuki dealer near you who has the equipment needed to locate the source of the problem and the knowledge to use it. If not, the easiest-but not necessarily the cheapest-solution may be to buy and try the least-expensive sensor first, and if it doesn’t remedy the problem, buy the other. That ’s not how I normally prefer to do things, but desperate men sometimes have to make desperate moves. □
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.
