Service
SERVICE
PAUL DEAN
Scheduled executions
Q Have you ever heard of instant battery failure on a motorcycle? In the past 15 years, this has happened twice to my 1986 Yamaha Maxim X. Both times, the battery has given no signs of imminent failure, always starting the engine just fine. But then, almost like a fuse, the battery would give off a “snap” and there would be no power at all. Both batteries were about 5 years old when this happened, so I really can’t complain about battery life. It’s just that instant battery failure could have left me stranded with no warning if it had occurred when I was a long way from home. Do you think my Maxim X generates some sort of harmonics that cause a battery’s internal connections to break, or do Yuasa batteries have a built-in clock that causes them to instantly fail in five years? Erwin Makincn Posted on www.cycleworld.com
A As far as I know, Maxims of that era were not programmed to murder their batteries at predetermined intervals. Neither is Yuasa in such dire financial straits that management has resorted to sabotage just to keep the ship afloat. Battery failure every five years is not tragic financially but, as you state, it could be troublesome in other ways.
I suspect that engine vibration has played a leading role in the sudden demise of your Yuasas. I haven’t ridden a Maxim in a while, but I don’t recall them vibrating any more than most comparable four-cylinder bikes, and neither are they renowned for instant periodic battery failure. So there probably is something about your particular motorcycle that is causing the problem.
Most logical is the battery mounting itself. Is the battery tray securely attached to the frame? Are the battery’s hold-down strap and rubber insulating mat still in place and in decent condi-
tion? These are small but important things to check, because their absence or poor condition can have an effect on the nature of any vibration reaching the battery. The motor mounts also could be a factor. Are all the mount bolts tight? What’s more, the Maxim’s right-side front frame downtube is detachable to facilitate engine removal and installation, and its attachment bolts also must be tight, lest it help transmit certain vibration frequencies that kill the battery.
Also, let’s not forget that motorcycles are manufactured items involving countless things that can vary from one bike to another-welded joints, high-stress areas, engine-component tolerances, human error in assembly, etc. As a consequence, no two are absolutely identical. Some vibrate more than others, some transmit vibration to certain parts of the machine more than others. Your bike may be one that delivers a frequency to the battery that causes an internal connection to fatigue and eventually break, resulting in instant battery failure. If so, you may be able to prevent such an outcome by using more or different insulation between the battery and its mounting tray. It could take at least five years to determine the success or failure of such a modification, but that prompts another question: How long do you plan to keep your 22year-old Maxim on the road?
Of primary concern
QI own a 2004 Harley-Davidson XL883 Sportster that I purchased new. Problem: At 70-71 mph in fifth gear, it gives off a rather intense vibration that feels like the engine is going to take itself apart. I can duplicate the same vibration in fourth gear at the same rpm. The only modifications I have made are a carburetor kit, a K&N air filter and Screamin’ Eagle slip-on mufflers (with baffles). Help... Charlie Fearing Union, Maine
AHmmm. Another vibration issue, it would seem. First thing I would check is the adjustment of the primary chain. The chain gradually loosens as the result of normal wear; when the slack becomes excessive, the top and bottom runs of the chain can slap up and down in the primary case enough to make the bike shudder like crazy. The symptoms of a loose primary chain usually appear first as low-rpm jerkiness; but depending upon the degree of looseness, shuddering at higher rpm is also an indication. The Sportster has a chain adjustment shoe in the primary case; I suggest you either purchase a shop manual, which outlines the adjustment procedure in detail, or take the bike to your H-D dealer to have the work done.
If the primary chain proves not to be the culprit, check all the motormount bolts. If they have worked loose, they can allow the bike to shake like the engine is trying to jump out of the frame.. .because that’s exactly what it’s attempting to do. And while you’re at it, check the frame for cracks and broken welds, especially at the junctions of tubes. Either of those conditions will also produce the paintmixer symptoms you describe.
Candid Cameron
QA recent article on engine balancing in a British classic-bike magazine was informative but left out some answers I needed. Can you explain balance factor and its applications, specifically for a parallel-Twin (Triumph 650)? I know an engine that has been balanced will not only be smoother running but will last a little longer due to less stress on moving components. Were Triumphs balanced at the factory? Jeff Carruthers ' Calgary, Canada
Ain a British parallel-Twin, the two pistons move up and down together, so the balancing issues are exactly as they are for a Single. So let us consider this step by step. As a first step, let’s attach to a point 180 degrees away from the crankpin counterweights that will prevent the assembled crank from rolling away when supported on a pair of level straightedges. The weight of the rods and pistons is hanging down from the crankpin, exactly balanced by these counterweights. Now consider what happens as the engine rotates. At TDC, the rising pistons are trying to jerk the crank upward with considerable force as they decelerate to a stop. And 180 degrees away, our counterweights are yanking downward with exactly equal force. This is good, just what we want.
Now imagine the pistons at BDC, where they have just decelerated to a stop. As they decelerate, they yank the crankshaft downward. But above them, 180 degrees away, our counterweights are yanking upward with equal force. Again, well and good.
Here is where the trouble arrives. At 90 degrees after TDC, the pistons are near their maximum speed and are not accelerating or decelerating, so they exert little force on the crank. But 180 degrees away, our heavy counterweights are yanking the crankshaft backward with a large force. And at 270 degrees, the mirror-image situation takes place, with the pistons near their top speed, exerting little force on the crank, but the counterweights yanking the crankshaft forward with a large force.
What we have done here is simply change an engine that vibrates heavily up and down into one that now vibrates just as hard, but forward and backward. The reason is that while the pistons move in a straight line and exert shaking forces mainly only near the ends of their motion, the counterweights move in a circle and exert an imbalance force all the time. Thus, the engine is balanced at only two positions— TDC and BDC-but when the counterweights are at 90 and 270 degrees, they shake the engine forward and back very hard.
The compromise answer is to counterweight not all the weight of pistons, pins, rings and small-end of the rod, but to counterweight only half of it. This cuts peak shaking force on crank main bearings in half, resulting in an engine whose shaking force rotates instead of just jumping up and down, and rotates opposite to crank rotation. This is the very best that can be done with crankmounted counterweights. Full balancing can be achieved but it requires adding balance shafts-something the motoring public did not want to pay for when British Twins were first designed. In fact, people were delighted with parallel-Twins, which felt much smoother than did Singles because they did not propel the bike with such large thumps.
Now it gets a little more complicated. British Twins are not, in fact, balanced at 50 percent of the reciprocating mass (pistons, rings, wristpins and small-ends of the rods). Instead they are “overbalanced” at more like 65-80 percent. The reason is that the rider feels up-and-down vibration much more, and forward-andback vibration less. Therefore, British Twins were balanced to a point of best feeling. A variety of cranks was made up with different balance factors, and test riders evaluated how they felt. The crank balance factor that got the most votes was the one that was then adopted for production.
If your engine were given a set of primary balance shafts (rotating at crank speed), there would still be a secondary imbalance force about VA the size of the original primary imbalance (secondary means at twice crank frequency). In some large four-cylinder engines, secondary balance shafts are included to suppress this “buzzy” shaking force.-Kevin Cameron
2005: A spacer odyssey
QI just replaced the front-wheel bearings on my 2005 Kawasaki Z1000, and now the wheel won’t turn. The only way I can get it to rotate is to loosen the axle nut. As soon as I apply even a little torque to the nut, the wheel gets hard to tum, and if I tighten it any farther, the wheel locks up. I have removed and installed the wheel several times to make sure I put the outer spacers back in correctly, and the entire assembly slides into place perfectly between the fork tubes, but I can’t tighten the axle nut and also have the wheel turn. Got any idea what the problem might be?
Tom Duncan Utica, New York
A The left and right outer frontwheel spacers on a Z1000 are identical and will only fit into the wheel-bearing seals in one direction, so it’s impossible to install them improperly. My best guess, then, is that you either forgot to reinstall the long tubular spacer that fits inside the hub, between the two wheel bearings, or
that you didn’t get one or both of the bearings fully seated in their mounting bosses. The force of tightening the axle nut tries to pinch the two fork legs closer together, and that long spacer has the exact dimension required to prevent the inner races of the two ball-bearings from also being squeezed together. If the races are forced more than a few thousandths off the centerline of the bearing, the balls get bound up between the inner and outer races, causing the bearings to lock up. The wheel bearings in a car do not require any such spacers because they are tapered rollers designed to be pulled together, but motorcycles use ball bearings that are not.
If you in fact have put that inner spacer back in place when installing the bearings, the problem most likely is that the new bearings are not fully seated. This usually is caused by debris in the bottom
of the mounting hole. The debris could be either residual grime or small slivers of aluminum that got peeled off the walls of the boss during bearing installation. I don’t know what method you used to install the bearings, but if you hammered or pressed them into place, you could have inadvertently scraped off those slivers in the process, and they prevented the bearing from seating in the bottom of the boss.
My advice is for you to remove both bearings and throw them away; the pinching force they have undergone while you’ve been tightening the axle nut has put tiny indentations in the races and balls that will lead to premature failure. Then thoroughly clean out the bosses before installing new bearings. The job will be made much easier if, just prior to installation, you chill the bearings in a freezer and heat the wheel hub. Ideally, the hub should be heated in an oven to at least 250 degrees. But if you’re careful, you can heat it with a propane torch; if you’re patient, you usually can get it hot enough with a heat gun. The combined expansion of the inner diameter of the mounting boss and the contraction of the bearing’s outer race reduces the interference fit between the two, possibly even enough to let the bearing drop all the way to the bottom of the boss without any force whatsoever. But regardless of how you install the bearings, be absolutely certain that they have fully seated against the shoulder at the bottom of their mounting bosses. >
Recall Roster
NHTSA Recall No. 07V576000 Honda CBR1000RR Model years: 2006-07 Number of units involved: 25,422 Problem: These motorcycles have an improperly welded vent pipe in the bottom of the gas tank. Due to vibration, these welds may crack and allow fuel to drip. Fuel leakage in the presence of an ignition source can result in a fire. Remedy: Dealers will inspect and replace the gas tank. Owners not receiving this free remedy should contact Honda at 866/784-1870.
NHTSA Recall No. 07V580000 Big Dog 2005-08 Mastiff; 2005-07 Chopper; 2006-08 K-9; 2005-07 Bulldog; 2008 Mutt
Number of units involved: 8061 Problem: The rear-fender strutattaching bolts on these motorcycles can fail, allowing the fender to detach from the motorcycle. This could occur without warning and result in an injury or a crash.
Remedy: Dealers will remove existing strut bolts and replace with highertensile-strength bolts and updated washers. Higher torque values will be used when installing the replacement fasteners. Owners who do not receive this free remedy may contact Big Dog at 316/267-9121.
Exhaustive research
QIn reading your magazine and numerous others, I have gotten the impression that some aftermarket exhaust systems can cause a loss of power at lower rpm, even if they help the engine make more power at higher rpm. Is my assumption correct, and if so, why does this happen? Elton Simmons Reading, Pennsylvania
Alt happens because most motorheads are obsessed with peak horsepower numbers. The aftermarket exhaust manufacturers therefore have learned that the best strategy for marketing their systems is to claim significant increases in peak power. And very often, their claims are true, even if not by as large a percentage as they allege. The problem is that rarely can the tuning of any one exhaust system provide the best possible performance at all rpm. Usually-but not alwaysobtaining more peak power over a stock system calls for a decrease in exhaust back-pressure, allowing the engine to breathe more freely at high rpm; but at lower engine speeds, obtaining the best torque numbers usually requires a different level of back-pressure than at higher revs. So, understanding the public’s fascination with big hp numbers, the pipe companies tend to concentrate on designing exhausts that will yield the highest peak power output, even if it means a loss of lower-rpm performance-not to mention a substantial increase in exhaust noise.
The motorcycle manufacturers are not unaware of or unconcerned about their customers’ desire for max power. But those companies have very restrictive sound and exhaust-gas emissions standards to comply with, and those regulations greatly complicate their ability to build bikes that produce as much sheer power as would otherwise be possible. They nonetheless do a remarkable job of designing performance engines that pump out phenomenal horsepower numbers yet still are amazingly torquey and tractable throughout the lower and middle rpm ranges.
Air not so apparent
QI have a question involving the air pressure in my bike’s tires. The owner’s manual calls for 33 psi; the dealer put 36 in the front and 39 in the rear; yet the tires, which are Dunlops, both show 41 psi. What pressure should I be using? R.E. Wells Norfork, Arkansas
AAn ongoing problem for tire manufacturers is not concern about what they know but rather about what they don’t know. They don’t know for certain what kind of bikes their tires will be mounted on; they don’t know how much any given rider and, when applicable, his/her passenger will weigh; they don’t know how any given bike will be ridden or loaded or what condition it might be in. And since all of those factors can have an effect on determining the optimum tire pressure, the manufacturers play it safe and list on the tires the maximum load the tire can safely support at the maximum recommended pressurewhich, on your tires, explains the 41 psi number molded into the sidewalls.
Meanwhile, most of the owner’s manuals that offer tire-pressure information suggest a range of pressures based on either two-up or solo riding; the same information is often found on a sticker somewhere on the bike. Those recommendations are largely based on the brand, model and size of tires that come on the bike as standard equipment, but they also are pretty accurate for any comparable tire.
You didn’t mention what kind of bike you ride, so I can’t offer you specific pressure information. But if you are anywhere near average weight, won’t be doing any racing or track days and don’t have heavy aftermarket equipment on the bike, you won’t go too far wrong with the recommendations in the owner’s manual.
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 949/631-0651; 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 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.
