Service
SERVICE
PAUL DEAN
Suzuki fat boy
Q I want to put a wider rear tire on my Suzuki M109R this year. The stock size is 240mm, but I would like to replace it with a 250 or 280mm tire. Is this possible without changing or modifying the wheel? I want to be FAT! Timothy Doolittle Pawling, New York
A If that's your objective, I suggest you engage in a conscientiously applied program of Twinkies, Ding Dongs and long afternoons spent in a La-Z-Boy watching Jerry Springer. Oh, wait, I get it: You want your rear tire to be fat, not your rear end! Well, in that case, you're in luck. Suzuki's engineers evidently felt that some 109 owners would want to install wider rear tires, because they provided plenty of clearance between the stock 240 rear meat and both sides of the swingarm. There in fact is sufficient room to allow a 280mm tire to fit without it making contact with anything, either horizontally or vertically. You can even lower the back of the bike more than an inch with a 280 tire on the rear and not encounter any fender-clearance problems. Ideally, a 280 tire should be mounted on a wheel that's an inch or an inch-anda-half wider than your 109's original 81/2~ inch rear. EgoTripp (www egotripp wheels.com; 800/741-1814) in Lubbock, Texas, offers a 10-inch-wide billet wheel that bolts right onto a 109. But it's not a cheap swap: Pick any of the company's
30 different wheel designs and the 10incher will put a $1490 dent in your bank account. Send them a design of your choice-plus another two grand-and they'll even machine a one-off custom wheel just for you. If a new wheel is too rich for your blood, you could always just spoon the 280 onto the stock wheel-though that would pinch the sidewalls in quite a bit and detract from the fat-tire look you're after. It also would slightly increase the curvature of the tread. I've never ridden a 109 with a 280 tire on a stock wheel, so I don’t know precisely how the handling would be affected with such an arrangement.
I can tell you, though, that with a rear tire that’s more than 11 inches wide, the resistance to leaning into a comer that a stock 109 already exhibits will be noticeably increased. That extra width will also make the Suzuki want to stand up when you apply the brakes while trying to lean into a corner. But I suspect that appearance is more important to you than handling performance; if so, the trade-off will probably be worth your while.
Rubber match
Q In the September, 2006, issue, you answered a question from Ronald Glaum ("Hoop dreams") regarding the reason motorcycle tires wear out so quickly compared to automobile tires. Okay, so now I understand what that's all about, but why do bike tires also have to cost so much? Combined with the high prices shops charge for labor, the expense of installing new tires is just too much!
Tim Allen Posted on aol.com
Ain the end, it mostly boils down to a matter of volume. Depending upon whose statistics you believe, there are somewhere around 30 times more automobiles in this country than motorcycles, and each one of those cars requires 2 Vi times as many tires (4 per car, plus a spare). Add in other vehicles that require more tires each-such as dually pickups that need 7-and you soon find that for the sale of each motorcycle tire, more than 100 car tires are sold.
In manufacturing of just about any kind, higher volume equals greater efficiencies equals lower per-unit prices. If a company is manufacturing 600,000 of a certain model of tire, that tire obviously is going to cost less than if only, say, 20,000 were made.
Besides, what makes you think bike tires cost more than car tires? If you exclude the models intended for racing or track days, bike tires are priced anywhere from the $30-40 range up to the mid-$300s, and so are car tires. Some high-end highperformance car tires cost more than $400 apiece, as do a few specialized race/track-day bike tires.
As far as the costs of mounting tires goes, once again, that same economy of scale dictates the market. There are thousands upon thousands of retail cartire stores across the country but none that sell only motorcycle tires. And even though most gas stations have morphed into convenience stores, many of them still mount car tires for next to nothing. So there are countless places to have car tires installed by low per-hour labor. But bike tires are changed by motorcycle dealers and repair shops that have $65 or $70 an hour labor rates. Adding to that expense is that most bike tires are more difficult and time-consuming to change than car tires.
In the end, all of this is easily explained by the very same fact I stated in my September response to Mr. Glaum: Though both have wheels and internal-combustion engines, a motorcycle is not a car, so comparing one to the other is not likely to provide meaningful results.
H-D mystery valve
QI recently had an exhaust-
valve problem with my 2005 Harley-Davidson Road King. The bike is bone-stock with about 13,000 miles on it. About nine months ago, the engine started making ticking noises emanating from the top of the rear cylinder on startup that subsided after 30 seconds or so; it almost sounded like there was no oil in the engine. The dealer determined it was a faulty rear-cylinder exhaust valve. I saw the components and the valve was indeed very discolored from the heat, and a fair amount of carbon deposits were evident on both the valve and the seat. The problem was under warranty, so it was fixed to my satisfaction and hasn’t resurfaced since.
I asked the dealer what would have caused this and he told me it more than likely was a factory misadjustment of the exhaust valve that would not let the valve close completely. I wasn’t sure I bought his explanation and was wondering if the fact that the problem occurred on the rear cylinder of an air-cooled bike maybe had something to do with it. Jim Vanden Eynden
Hamilton, Ohio
A Although I commend your
dealer for honoring your Road King’s warranty, his diagnosis of the problem doesn’t make sense. Perhaps you misunderstood him. If your bike really is as bone-stock as you claim, the valve could not have been misadjusted at the factory. Like all modern H-D Big Twin and Sportster engines, Twin Cam motors have hydraulic tappets, and in stock form, they require no valve “adjustment”; the pushrods are onepiece, with no provisions whatsoever for adjustment, and ditto for the rocker arms. The valvetrain components are manufactured with just the right dimensions to keep the hydraulic lifters’ internal pistons working within their requisite range of operation. Even if one of the pushrods was several thousandths shorter or longer than the others, it would not cause the valve problem you describe.
Besides, if the valve had not been fully closing from the time the bike left the factory, problems would have surfaced immediately or soon thereafter. Hard starting, weak idle and a shortage of power would have been the most obvious, with the condition steadily growing worse. Even if the symptoms didn’t show up until recently, you never mentioned any kind of performance drop-off. So your description of the problem doesn’t seem to match the dealer’s explanation of its cause.
When an engine with hydraulic lifters makes a valve-related ticking noise upon startup, then the noise goes away almost immediately, 99 times out of 100 it’s because one of the lifters “bled down” while the engine was stopped. This sometimes happens when the little check ball in the lifter fails to
maintain its seal, usually due to a tiny piece of contamination in the oil. The bleed-down causes the lifter to allow excessive valve clearance that’s evidenced by the ticking upon startup; but as soon as oil pressure successfully pumps the lifter back up again, the excess clearance is taken up, the lifter behaves normally and the noise goes away.
Most importantly for this discussion, bleed-down never causes a valve to hang open. And the fact that the ticking occurred on the rear cylinder of an aircooled engine is irrelevant. There usually are temperature differentials between front and rear cylinders, but not enough so to cause the kinds of problems described here.
600s in drag
Q After reading the quarter-mile time of the new Honda CBR600RR (10.56 seconds @ 130.77 mph) in the March issue, I am again perplexed by the ability of the 600 racereplicas to run times faster than largerdisplacement machines with far more horsepower and considerably more torque. Most of the naked bikes in your October, 2006, comparison, for example, had significantly higher torque and horsepower figures and weighed between 40 to 80 pounds more than the Honda, yet only two covered the quarter-mile more quickly, and not by much. How do the 600s do it? Is it just the weight and the fairing?
Jim Hohmann Langhorne, Pennsylvania
A As any knowledgeable drag racer can tell you, the launch is the most critical part of a quarter-mile run. Even the tiniest bobble or hesitation when coming off the line can knock two or three tenths off the E.T. And that’s
where the bigger bikes struggle the most. Yes, they do make more torque, but that just makes them harder to launch. Most of the larger-displacement, more-powerful performance bikes have relatively short wheelbases, with high centers of gravity necessitated by the need for generous cornering clearance. As a result, they transfer so much weight to the rear wheel when accelerating in the lower gears that the use of full throttle, especially in first gear, is virtually impossible, lest the bike wheelie over backward. This tendency can be even worse on naked bikes, which sit their riders in an upright position that helps transfer even more weight to the rear. Consequently, launches on these big machines are not at all reflective of their true acceleration potential. But once they get “out of the hole,” they can be turned loose at wide-open throttle and accelerate in a manner befitting their exceptional power-to-weight ratios.
Except that as speeds approach and then exceed the 90-to-100-mph mark, the absence of a fairing on naked bikes penalizes them once more. Wind resistance increases exponentially with speed, so these bikes don’t slip through the air as easily as a fully faired machine. That hampers their acceleration on the top end, adding another couple of tenths to their E.T.s.
A fully faired 600, conversely, is easier to launch at or near full throttle, and its “slipperier” aerodynamics pay dividends during the latter half of the quarter-mile. So while the smaller-engined bike doesn’t make as much sheer power, its power-toweight ratio isn’t all that far off that of a bigger bike, and it is able to take better advantage of the power it does have.
Ask the Dudester
QRyan Dudek, you’re the man! I mean, Last Man Standing, Erzberg, Endurocross, Dakar bikes...you have my attention, sir! So, could you please tell me how many ounces of flywheel weight it takes to tame the Honda CRF450X for expert technical trail riding? And can the weak electric starter still turn a heavier flywheel? Fm not completly sold on a Rekluse clutch to smooth the power delivery.
Dennis Duane Hurley
Posted on www.cycleworld.com
Aí posed your questions to Ryan “Dude K” Dudek, and his response was, “I recommend that before you add flywheel weight, you try two other steps. First, get an NCYS carb needle from Keihin and put the clip in the third position. This should smooth the power a bit and get rid of the little hiccup oft' the bottom. Second, try using a larger rear sprocket. The stocker has 51 teeth, so go up to a 53. This is a cheaper and easier alternative to a flywheel weight. "If these fixes don't work for you and you still want to add a flywheel weight, don't go too heavy. Six to eight ounces should be sufficient. If you add much more weight, the motor will lose its snap and peppiness. Also, the starter is not weak; it just spins slowly. Six more ounces of flywheel will not adversely affect it."
Supermoto you tube
Q Back when supermoto began getting popular, some riders started putting wider rims and what sure looked like tubeless tires on wirespoked dirtbike wheels. In fact, many still do. I am in the process of convert ing an old Honda XR for street use and would like to lace up some sporty gumballs on spoked wheels. Can I do this using tubeless tires without tubes? I would really like to run sticky modern tires but without the unsprung weight and rotating inertia of tubes.
Tim Freeman
Mineral Point, Wisconsin
A Euro Choice Imports (www eurochoiceimports.com 303/8878034) markets a product called the LP Tubeless Kit that allows tubeless tires to be safely mounted on wire-spoked wheels. Installation is a three-step process in which you first apply provided stickers atop every spoke nipple. Next is a gel-like adhesive strip that wraps around the well of the rim and seals the spokes from the inside. The final step is to wrap the well with a carbon-Keviar outer band that holds the stickers and sealing strip firmly in place. The spokes still can be adjusted without causing any leakage problems or requiring removal of the kit.
Euro Choice claims the kit makes any given tire/wheel combination as much as 2 pounds lighter than it would be with a regular tube, and that the reduction in weight has proven to shave up to a halfsecond off of lap times. The kit is designed for supermoto racing only, though, and not for road bikes. The importer doesn’t give a reason, but one has to assume that the extreme speeds attainable by so many streetbikes, along with the considerable tire heat they can generate, could overwhelm the kit’s ability to maintain a good seal. A sudden deflation at 150 mph could be disastrous.
The kit was designed by multi-time European enduro champion Laurent Pidoux, and it has been tested and approved by numerous accomplished supermoto racers, including Fabrice Lecoanet and the Chambón brothers, Stéphane and Boris. The kits are available to fit 17-inch wheels from 3 to 5.5 inches in width, and for a 3.5-inchwide 16.5-inch wheel. But they aren’t exactly cheap: Expect to shell out $119 per wheel.
Ouch! □
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.
