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PAUL DEAN
R6 realine red flag
Q I can understand how brown can be the new black, but is 16,200 rpm the new 17,500 rpm? Some British bike magazines have reported that the 2006 Yamaha YZF-R6 does not rev higher than 16,000 rpm, even though the tach shows 17,500 when the rev limiter cuts in. How come you guys did not pick up on that? In fact, you gave it a test that was so good, I went to a Yamaha dealer and ordered one based on your review. Now I find out that it doesn't rev that high and that the limiter is set 1500 rpm lower. What gives? Do you guys not test everything? I feel misled by you as well as by Yamaha.
Zach `Zachopoulos North Liberty, Iowa
A I'm sorry you feel you've been duped, but so do we. As of the time this issue went to press, Yamaha here in the U.S. had not yet made any R6s available for magazine evaluation, so we’d not had the chance to submit one to our usual testing regimen; otherwise, we would have discovered the redline discrepancy when running the bike on our dyno. The article we published in the February issue was not a test but rather a “First Ride” based on Don Canet’s brief time aboard a new R6 at the Losail International Circuit, a racetrack in Qatar. Under those conditions, he had no means by which to discover that the tachometer was grossly inaccurate. All he was able to determine was that the bike is very fast, very light and handles brilliantly. The British bike mags learned of the redline problem only after they, as well as some dealers and owners there, put new R6s on dynos and observed differences between the bikes’ tachs and the dynos’ tachs. They were able to beat American magazines to the punch with this revelation simply because the new R6 was released for sale and testing in Europe well before it was in the U.S.
Yamaha has admitted its error, although the company gave no concrete reason for such an egregious screw-up. It’s hard to imagine how on Earth a new model could be equipped with a 17,500rpm tachometer-and the company’s tech people and publicists would be permitted to make such a big deal about that astronomical redline-yet no one in the long factory-to-dealership pipeline seemed to notice that the engine wouldn’t rev nearly that high until the bike got into the hands of the public.
A logical person might conclude that in actuality, the new R6 engine was originally designed to rev to 17,500, so vendors supplied tachometers with the redline set at that rpm, but that a late-arising reli ability problem forced a last-minute re duction in peak engine speed to 16,000 rpm, and that no other tachs were readily available. I have not one shred of evi dence to support such an opinion, but it's clear that something very wonky is go ing on here.
Regardless of the reason for the mis take, Yamaha has sent a letter to every 2006 R6 owner offering to buy back the bike for the entire purchase price, in cluding taxes, set-up fees and any inter est paid in connection with the initial purchase of the bike. Owners are not obligated to sell their bikes back to Yamaha. but anyone who is dissatisfied with their new R6 because of this redline discrepancy can receive an entire refund, no questions asked. -
If you have not yet taken delivery of your R6, you probably can cancel the sale if you so wish, with no opposition from the dealer or from Yamaha. And if you are in possession of the bike and are displeased with its 1500-rpm shortfall, return it; this is one of those rare instanc es when a dealer will take back a motor vehicle and refund all of your money without any muss or fuss.
The geometry of geometry
I have been an avid rider for go ing on 37 years now, yet despite all o my experience, I have a question I am almost embarrassed to ask, but I must: What are the exact locations used to determine "trail?" I understand what "rake" is, but I have gotten conflicting descriptions of trail over the years. Could you please explain this with a drawing? I need to settle the matter once and for all.
Ric Bertling Dubuque, Iowa
A No apologies needed; I know quite a few people who've been major players in the motorcycle business all of their lives but don't know what trail is, either. The accompanying illus tration should make not just trail easier to understand, but rake, as well, since some folks aren't very clear on that sub ject, either.
As depicted in the accompanying ii-. lusiration, imagine a line that runs right through the center of the steering head and extends all the way down to the ground; as you can see, that line inter sects the ground ahead of the front wheel. Now imagine another line, a vertical one that passes right through the center of the axle and also intersects the ground, this time right in the middle of the tire's con tact patch. The distance between those two lines, measured right where they meet the ground, is the trail.
Note that the angle between those two lines is shown as the rake, which bike designers usually refer to as the "steering-head angle." Many people are of the belief that rake is measured by the angle of the fork legs, but that's not true. It is if the legs are mounted in their triple-clamps at the same angle as the steering head; but if they are notwhich is the case on some bikes-the rake has to be determined by the steering head angle. And in any event, calculating trail always involves a line drawn through the steering head, not through the fork legs.
One-lung Virago
Q My `85 Yamaha Virago will run fine for a few seconds, then one of the cylinders apparently just shuts down-either no spark or no fuel. My very knowledgeable mechanic friend has tried everything from carb rebuilds to a new ignition box and a lot more stuff in between. Now he's stumped. None of the cycle dealers in town will even look at the bike because of its age, and Yamaha has failed to help me. Do you know any one who might know what this bike needs?
David Ansell Posted on America Online
A Sorry to learn of your troubles, David, but I suspect that a signif icant part of the problem is your "very knowledgeable mechanic friend." It's not my intention to put him down, be cause I'm sure he's a great guy who means well; but any mechanic who re ally knows his stuff would have at least isolated the condition to an absence of either fuel or spark, even if he couldn’t pinpoint the exact cause.
CONTINUED
I may be able to help you diagnose the problem on your own. First, start the engine and let it run until the affected cylinder stops operating, then immediately close the fuel petcock and turn off the ignition. By “immediately,” I mean you should sit on the bike with one hand on the petcock lever and the other on the ignition switch, and the instant you hear the affected cylinder stop firing, turn both off. Then very carefully drain the carburetor float bowls, one at a time, in separate small containers. Both containers should end up with the same amount of fuel; if they don’t, there’s a fuel-delivery problem with that carburetor, possibly a float that’s sticking closed.
If that’s not the source of the cylinder’s lack of combustion, find a couple of good used (or new) sparkplugs and keep them within reach while you restart the engine. Again, the instant one cylinder quits firing, shut off the ignition, pull off both plug wires, push them onto the spare plugs and ground the body of both plugs on the cylinder head. Turn on the ignition and hold down the starter button while checking for spark across the gaps of both plugs. If one is not firing, there’s a problem in that cylinder’s ignition circuitry. For further verification, switch all the wiring on the two ignition coils to see if the other cylinder stops firing; if it does, you’ll know that the problem is in that particular coil.
There are so many possible causes of your Virago’s problem that I couldn’t cover them all in this very limited space. But if you or your friend use a logical process of elimination like the one I have described here, you’re bound to discover the cause.
Buell with an attitude
Q I have two questions regarding your "Quick Ride" of the Buell XB12Ss Long in the November, 2005, issue. First, all of Buell's literature claims fuel economy around 70 mpg highway, but I have yet to see any review come anywhere near that number. Second, you rode the Long in Colorado for that > "Quick Ride" and stated that the alti tude affected performance. I was under the assumption that fuel-injection was supposed to eliminate this kind of alti tu~ problem.
Bryan Wells Filer, Idaho
A Let's start with fuel mileage. If you were to ride the J3uell like you were taking Miss Daisy to the store, you probably could get 70 mpg, if not more. And I suspect that when com ing up with their mile age figures, Buell's peo ple rode very conservatively and with a gentle throttle hand to get the highest mpg reason u~y possible. But when magazine ed itors test motorcycles, they do it using real-world mixtures of riding styles and techniques that include stop-and-go, commuting, casual cruising and, espe cially with performance-oriented models, full throttle up through the gears in the meat of the powerband. That combina tion will never net fuel-mileage num bers equal to those claimed by a manu facturer.
Now let's talk about fuel-injection and your apparent misunderstanding of the benefits it offers compared with carburetors. At high altitudes, carburet ed engines run rich because the air is so much thinner than it is at lower alti tudes; but the jet sizes of the carbs re main the same, so they still deliver about the same amount of fuel. Thus, the engine runs poorly because it not only gets less air during each intake stroke but also receives too much fuel for those conditions.
Fuel-injection remedies half of that problem. Through data provided to the ECU (the black-box computer) via one kind of air-density sensor or another, the system "knows" when the air is thinner, and it automatically reduces the amount of fuel injected into the intake. But no matter what kind of fuel adjustment the system makes, it can't compensate for the thinness of the air. So, although the air-to-fuel ratio remains correct at high altitude, less air is drawn into the engine with each intake stroke, which means there is less overall mixture. Conse quently, the engine makes more power than it would if it were carbureted but less than it would at lower altitudes where the air is heavier.
