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Vibration to the Max

Paul Dean

We have an ’86 Yamaha V-Max and would like to know what the effects would be of removing the counter-rotating balancing shaft altogether. Paul at MadMax could only tell us that it would open up a can of worms. Obviously, there would be a certain increase in the amount of vibration, but can we actually do without the balancer and not damage the engine? I would be very interested to hear any theories you have on the subject, or hear from anyone who has actually done this.

Helen Doughty Posted on America Online

I don’t know of anyone who has simply yanked the counterbalancer out of a VMax engine, so I can’t tell you anything factual about the effects of its removal. In morphing the V-Max powerplant into the Royal Star motor in 1996, Yamaha did away with the counterbalancer, but the engineers also made other significant modifications to the basic design to compensate. Most notably, they increased the crankshaft’s balance factor from 50 percent (which is typical for a counterbalanced engine) up to around 70 percent (the normal range for non-counterbalanced engines). What’s more, the Royal Star makes just half the horsepower of a VMax and only spins at about half the peak rpm, factors that have a dramatic effect on the motor’s vibration potential. It’s my semi-educated guess, therefore, that unless you have the crankshaft rebalanced with a higher balance factor, removing your V-Max’s counterbalancer will likely cause the bike to shake like a hardware-store paint mixer.

Tiny dancer

Ever since I bought my 2001 Suzuki Intruder 800, it has had a high-speed wobble. At any speed above 65 mph, leaning in the least or crossing the seam in the asphalt between lanes will cause the bike to go into a wobble. On one recent occasion, the bike almost went out of control when it started wobbling at just over 75 mph; it took me about a quarter-mile to get it back under control.

I am a small female, just 4-foot-11 and 97 pounds, and the bike only does this when I am riding it. My husband is a 200-pound 6-footer, and the bike doesn’t wobble when he rides it. I’ve talked with numerous other Intruder 800 riders, and they don’t have this problem, but they all weigh at least 150 pounds. The mechanics at the local dealership have test-ridden the bike and claim there is nothing wrong with it, but they all weigh a lot more than I do, as well. At one point, I lowered the bike in the rear with shorter shocks, and fitted it with a small windshield and saddlebags. I’ve since taken them off, but the bike wobbled before those items were installed, it wobbled while they were in place, and it still wobbles after they have been removed. Please help! I like my bike and do not want to give it up. Betty Boop

Augusta, Georgia

Suzuki has sold tens of thousands of 700/750/800 Intruders since that model’s introduction in 1985, and I’ve been unable to learn of even one other instance of a similar wobbling problem. Neither have my contacts at American Suzuki. And save for two displacement increases, that model has gone largely unchanged over the years, particularly in its chassis design and steering geometry. So, at this point, I don’t have a clue what could be causing the aberrant handling behavior you describe.

Before sending you-or your mechanic-down what might be a long and arduous path of diagnosis, here ’s what I suggest: Try to wangle a ride on another 800 Intruder so you can compare its handling to that of your bike. Maybe one of those other Intruder owners with whom you have consulted would let you take a spin on his/her bike, or perhaps your dealer could arrange a test ride on one of his Intruders or that of another customer. If you get the same symptoms on another bike, you ’ll know that the wobble is inherent in the matchup of you and that particular model of motorcycle. In which case, you might try softer shock and fork springs, but even that might not cure the wobbles. A trade to another model might be the ultimate answer.

If however, you experience no such problems on another Intruder, you ’ll know that something indeed is wrong with yours. It will then be up to your mechanics to find the cause. Have them investigate all the usual suspects-the steering-head bearings, the swingarm-pivot bearings and the wheel bearings-but also get them to check the alignment of the rear wheel with the front. Sometimes, the accumulated manufacturing tolerances for the many and varied components between the front wheel and the rear can yield a rear-wheel misalignment, which, in turn, can cause handling and stability problems. The Intruder has shaft final drive, which offers no provisions for rear-wheel adjustment, so correcting this kind of misalignment can be a serious problem; but at least you will have found a probable cause of the wobbling. A motorcycle frame-repair shop might be able to correct the misalignment, but if not, the most logical solution would be, once again, to trade your Intruder for a different model.

Final-drive enigma

I am the owner of a 1998 Kawasaki Vulcan 800, and my question is twofold: What, if any, are the advantages and disadvantages of converting a chain-drive motorcycle to belt drive? And would such a change have negative impact on the engine? John Natiello

Posted on www.cycleworld.com

Answering the second question first, such a conversion would have no negative effect whatsoever on the engine. If anything, a belt final drive-which has more inherent elasticity than a metal chain-might better cushion some of the shocks that normally occur in the driveline, such as during shifts, when the throttle is rapidly snapped open or closed, and when the clutch is abruptly engaged. The problem is that the task of switching from a chain to a belt ranks somewhere between moderately difficult and practically impossible. Because a chain is considerably narrower than a belt of comparable strength, most chain-drive bikes do not provide sufficient room between the side of the rear tire and the frame to allow a belt to pass through. There also can be clearance problems in other areas, such as inside the case that covers the output shaft. On top of that, belt-drive pulleys are manufactured only in a very limited range of tooth counts, belt widths and modelspecific bolt patterns, whereas sprockets are available to fit just about any motorcycle or chain ever made. Belts also are available only in certain predetermined lengths that cannot be changed, whereas chains not only come in every conceivable length but can be quickly and easily altered.

So, in theory, switching from a chain to a belt final drive seems like a good idea. But in actuality, it is much more trouble than it’s worth.

Smooth operator

I just bought a brand new Honda CBR954RR. It’s a beautiful bike, but the abruptness of the fuel-injection (or maybe the driveline slop?) is so excessive that it’s impossible for me to be smooth when riding it. I’m not a fast rider, so all I got is smooth. What can I do to tame this wild bronco? Pogo25239 Posted on www.cycleworld.com

You ’ll never be able to get rid of the slack in the driveline, which we also pointed out during our June-issue test of the 954, but there is a couple of things you can do to smooth out the throttle response. First and least expensive is to take any excessive freeplay out of the throttle cables. Use the inline adjusters to dial-out most-but not all-of the play in the cables, then start the engine, let it idle, and turn the handlebars all the way to the left and all the way to the right, if the engine rpm increases even the slightest at either steering extreme, there is too little slack in the throttle cables. Adjust some back into them and then repeat the fullleft/full-right procedure.

A more expensive, but more productive, solution is to install a Dynojet Power Commander. For those who don’t know, the Power Commander is an aftermarket electronic device that supplements the original-equipment “black box’’ on most fuel-injected motorcycles. It allows adjustment of the fuel mixture-and if so desired, the ignition timing-to help overcome glitches in engine performance as well as meet the needs created by hop-up modifications.

Because of their need to comply with EPA emissions regulations, contemporary motorcycles have very lean fuel mixtures; and lean mixtures-especially off-idle-tend to cause abrupt throttle response, especially so on the CBR954RR.

The Power Commander helps eliminate some of that abruptness by richening the mixture, not just off-idle but everywhere else in the rpm range. There are two Power Commander models available for the 954: the model 110-211, which allows recalibration of the fuel-injection only, and the model 110-31 lr, which permits adjustment of both the fuel-injection and the ignition timing. If you log onto www.powercommander.com. you can get more information and even download free tuning maps specifically designed for the 954, whether bone-stock or equipped with various aftermarket performance exhausts and air filters.

On this site, you also can find the location of Dynojet’s Tuning Centers, where Power Commander-equipped motorcycles can have their own custom-tailored fuel-injection maps created. The dynamometers at these centers are equipped with an exhaust-gas analyzer linked to the bike’s Power Commander through the dyno ’s operating computer. While the bike is running on the dyno, the data from the analyzer is fed into the computer, which, using Dynojet’s proprietary Tuning Link Software, automatically programs the Power Commander to provide the optimum fuel-air mixture for all rpm and throttle openings. The entire procedure only takes a few minutes, and you ride away with an injection system that has been perfectly dialed-in for your bike ’s state of tune.

Back in the saddle

For almost five years, my 1995 Honda CB750 has been stored in a garage, parked and neglected, but I’m ready to ride once again. Problem is, after I hauled the bike out of the garage, replaced the battery and tried to start it, the starter just ran on and on without a peep from the engine. I’m thinking that the problem might be in the clutch (since it has to be engaged to start the engine), because when I try to bump-start it in gear with the clutch pulled in, the bike won’t roll an inch. What should I do? I need to ride. Meghan Mack Posted on www.cycleworld.com

FEEDBACK LOOP

I thought that your reply to the “Wheeler or dealer?” letter in the May, 2002, issue hit the nail right on the head. I am a senior who has been riding for a good many years now, and I can tell you that 98 percent of the dealers I’ve done business with have treated me like crap. They want to sell you a motorcycle, but once you sign the contract, they act like they really don’t care if they ever see you again. I put up with this treatment because I love riding and intend to do it until I can no longer lift my leg over the seat-God forbid. Mike Doyle

Camillus, New York

You’re not alone, Mike. Since replying to that letter, I have gotten an onslaught of mail-both electronic and conventional-from readers all across the country who feel just as you do about the rude, inconsiderate, deceitful treatment they routinely receive from motorcycle dealers. Many of those letters acknowledge that there indeed are good dealers out there, but that those shops can be hard to find, and are few and far between.

Your CB750 Nighthawk has trwo problems, neither of which is serious. First, the bike won’t roll in gear with the clutch lever pulled in because the clutch plates are not disengaging, the result of the bike having sat for so long. The clutch is “wet,” which means it operates in engine oil; and when the motorcycle is unused for long periods, the plates get so saturated with oil that they stick together.

After you get the engine running, you ’ll need to break the plates loose. To do this, leave the transmission in neutral with the engine warm and idling, and have someone give you enough of a push from behind (or coast down a hill) to get the bike moving between 5 and 10 mph. At that point, squeeze the clutch lever in and shift down into first gear; the bike will then chug along under its own power at low speed, even though you have the clutch lever pulled in all the way to the handgrip. With the lever still pulled in, quickly open and close the throttle, which will result in a short, momentary burst of acceleration followed by abrupt deceleration. Repeat this procedure until the clutch plates break loose, after which the clutch will then operate normally.

But first you’ve got to get the engine started, and the problem there is with yet another clutch. This one is a sprag clutch, a one-way device that allows the electric starter to turn the engine but will not allow the engine to turn the starter. It consists of three cylindrical, springloaded rollers that fit into tapered grooves and roll around on a race machined on the starter gear at the left end of the crankshaft. Over time, the oil residue on the rollers and race turns gooey, causing the rollers to skid when the starter is engaged, rather than rolling into their tapered slots and locking up the engagement mechanism. Any half-decent mechanic with basic knowledge of Japanese-bike workings should be able to take apart, clean and reassemble the starter clutch in an hour or so.

Mirages in my mirrors

I have a 1992 Yamaha Seca II, and as long as I’ve owned it, the mirrors have vibrated. Shaking and vibrating mirrors make it difficult for me to know what is behind me; to see clearly in them, I have to grab onto one of the mirrors with my hand to steady it. And for whatever reason, the right-side mirror vibrates more than the left. Do you have any suggestions that could help this problem? I’ve tried adding some rubber washers where the mirrors mount into the handlebars, but it didn’t help. Paul Ivey

Argyle Township, Maine

The problem of blurred rear-view images has bothered motorcyclists ever since someone clamped a mirror on a bike for the first time. Most contemporary bikes allow at least a half-decent view to the rear, but it wasn’t very long ago that the average motorcycle shook so badly that anything you saw in the mirrors looked more like a psychedelic light show than a view of the traffic behind. You couldn’t tell if the blurry image juddering around in your mirrors was a kid on a bicycle, a reflection of the billboard you just rode past or an 18wheeler about to turn you into road pizza.

By those standards, your Seca U’s mirrors are comparatively steady. But they do buzz quite a bit due to the four-cylinder engine’s secondary quite common for the right mirror to vibrate more than the left, because the rider’s hand is wrapped around the left end of the handlebar, dampening the buzzing somewhat. The rider ’s right hand, however, only grasps the plastic throttle tube, which does not fit snugly on the handlebar. This allows the right end of the handlebar to vibrate undamped and blur the mirror images more than on the left.

You can’t change the frequency of the engine ’s vibration, but you may be able to lower the frequency of the handlebars to the point where it is less sympathetic with that of the motor’s buzzing. The Seca II already has bar-end weights that help reduce the amount of vibration that reaches the grips and mirrors, but you can carry this damping effect even farther by adding more weight to the handlebars. You can accomplish this either by filling the bars completely with lead, usually in the form of buckshot, or by installing a product called the Bar Snake, which is specifically designed for this purpose. The Bar Snake is available from CP Products (408/449-7985) and come in two forms: a long, solid-rubber tube that fits inside the bars, or in liquid form that you pour into the bars and let harden. □

Got a mechanical or technical problem with your beloved ride? Can’t seem to find reasonable solutions in your area? Maybe we can help. If you think we can, either: 1) Mail your 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 CW1Dean@aol.com; or 4) log onto www.cycleworld.com and click on the Feedback button. Please, always include your name, city and state of residence. Don’t write a 10page essay, but do include enough information about the problem to permit a rational diagnosis. And please understand that due to the enormous volume of inquiries we receive, we can’t guarantee a reply to every question.