Service
SERVICE
PAUL DEAN
Terms of engagement
Q I have a question about engaging first gear when stopped. I have a 2009 Aprilia Tuono that I bought "new" this past year. It makes a moderate but unhealthy-sounding "clunk" when I shift it into first gear at a stop, but there is no significant lunge forward. When shifting into first gear with the engine running and the bike on a rear stand, however, the rear wheel immediately turns some, then stops. I get these results no matter how long I have the clutch disengaged and regardless of engine temperature, and the clutch doesn't engage until the lever is near the fully released position. The dealer says the clunk is normal, but I'm not convinced. It seems to me that the clutch is not fully disengaging, so the input shaft never stops turning, causing the clunk when I engage first gear. I am concerned that the transmission will be damaged. Could the bike having sat for over two years caused the clutch to drag?
Bill Huichinson Coral Gables, Florida
A T believe your dealer is correct: The noise you are hearing is normal and not an indication of any problem with the transmission or clutch.
If you were to take two perfectly flat plates made of metal or plastic or any hard material and coat their surfaces with a light film of oil, then press them together with considerable force, the adhesion of the oil would cause the plates to stick together when the force was relieved. You would have a bit of difficulty separating them by trying to pull them directly apart, but you could release them fairly easily by rotating one piece slightly while holding the other one stationary.
As you no doubt are aware, your Aprilia has a wet clutch. This means that its 19 plates (10 steel, 9 fiber) run in oil, so the same phenomenon occurs with them as with those hypothetical plates. Initially, the Aprilia's plates stick together when the clutch is disengaged because the transmission still is in neutral; thus, the entire clutch pack
keeps spinning because there is nothing to make the steel plates (which are con nected to the transmission input shaft via the inner clutch hub) stop turning at the same speed as the fiber plates (which are connected to the crankshaft via the outer clutch hub and primary drive). But when you shift into first, the steel plates are instantly forced to stop rotating while the fiber plates keep turning, and the momentary "sticking" of the plates to one another before they separate is what causes the clunk.
Your bike doesn't lurch forward when this happens, however, so the plates are not strongly resisting separation; they instead break loose easily and almost immediately. This is further evidenced by the fact that when the bike is shifted into first with the rear wheel off the ground, the wheel turns just briefly before stop ping. If the sticking condition were more pronounced, the wheel would continue turning until you either stepped on the rear brake or pushed the bike off the stand so the rear wheel would hit the ground.
Depending upon a number of factors (make and model of bike, clutch-plate material, brand and grade of oil, degree of plate separation upon disengagement and so on), most wet-clutch motor cycles emit a clunk when snicked into first from neutral, and many also lunge forward slightly, some more than others. Evidently, your Aprilia is one of the less severely afflicted, since it only makes a "moderate" clunk and doesn't lunge forward.
Bottom line? You have nothing to worry about.
Not a knock-knock joke
Q My 2008 Suzuki 1000 V-Strom has developed a knocking noise that seems to be coming from some where down in the engine cases. I only hear the noise at idle, and it goes away as soon as I open the throttle. Other wise, the engine runs perfectly. The V-Strom only has 8500 miles on it, and of the half-dozen bikes I have owned so far, I like this one the best, so I hope this knocking isn't a sign of an impend ing major failure. What's your opinion?
Jay Baker Submitted via America Online
A Over the past 15 years, I've rid den quite a few Suzukis powered by various iterations of the same basic 1000cc V-Twin engine that's in your V-Strom, and several of them have made knocking sounds like the one you describe. Those noises are not generated by failing components in the engine's bottom end but instead are the result of either one specific factor or a combina tion of several: a too-low or uneven idle; crankshaft side play that is at the large end of the allowable tolerance; fiber clutch plates whose tabs have become a loose fit in the outer clutch hub; and relaxed spring pressure in the auxiliary primary drive gear (a narrow, springloaded gear outboard of the drive gear on the crankshaft intended to maintain tension between the straight-cut primary gears, thereby reducing or eliminat ing primary-gear rattle). Usually, such sounds are barely perceptible on most Suzuki Vees, but accumulated wear and! or normal manufacturing tolerances can cause some of those engines to be noisier than others.
On any internal-combustion recipro cating engine, the crankshaft speeds up during each combustion event and then slows down until the next firing-an oc currence that is most evident at idle and
very low engine rpm. On a V-Twin, those firing pulses are staggered unevenlymore so with a 90-degree V-Twin (270°-450°) than on any other Vee spread-which can exaggerate inherent primary-drive noise and/or crankshaft side float. And if the idle is too low or erratic, the condition only gets worse.
To determine if the knocking on your V-Strom is idle-related, set the idle to 1200-1300 rpm; and while you're at it, check the adjustment of the Throttle Position Sensor (TPS). If you decide to do this work yourself, get a V-Strom factory service manual and follow the instructions for these tasks. If not, have a Suzuki dealer or a qualified indepen dent mechanic do the work. But even if in the end, the knocking either remains the same or is only marginally reduced, don't sweat it; such noises are normal on those V-Twins.
Phantom of the stopper-a
Q I recently completed a minor restoration on a 1996 Yamaha YZF600R that had been sitting in an
unheated garage for almost 10 years. I now have it running, handling and looking good, but the front brake is a problem. After just a few miles of rid ing, particularly at highway speeds, the brake starts to apply itself without me touching the lever. If I don't voluntarily pull over and stop, the brake will do it for me by locking up completely. If I park on the side of the road for a while, the brake releases and I can ride again for another three or four miles. I once took a wrench with me and cracked a bleeder open after the brake locked, and that allowed the wheel to turn freely. I got back home just as the brake started to bind up again.
Any idea what is going on here? Nice bike, but I'd like to be able to ride it more than a couple of miles at a time.
Sherman Covington Cicero, Illinois
A The problem most likely is with the return hole in the bottom of the master cylinder reservoir. That tiny hole serves two purposes: 1) It allows ad-
ditional brake fluid to enter the rest of the system as the brake pads wear, a process that gradually increases the internal vol ume of the slave cylinders in the calipers; and 2) it permits fluid to re-enter the reservoir when heat generated by the friction of braking (as well as by the very slight but normal "kissing" of the pads against the rotors when the brakes are not in use while the bike is being ridden) causes the fluid to expand. If that hole has been blocked by corrosion or fluid contamination-which could easily be the case on a bike that has been idle and subject to countless hot/cold cycles for an entire decade-it would cause the brake to lock in the way you describe.
As the fluid expands, none of it can pass back into the reservoir; so, the expansion causes the brake to start engaging, which generates more heat, which creates even more braking force, which then generates even more heat... You can see where this is going. The solution is to remove the master cylinder, check the condition of the bleed hole and clear it if it is blocked.
But wait-there's more. If you re placed the front brake lever during your restoration, you might have unknowing ly installed the wrong one. Many brake levers look alike, but even small differ ences in their pivot points and leverage ratios can alter the stroke of the piston inside the cylinder. If the piston does not retract far enough when the lever is released, the bleed hole will be obstruct ed, creating the same brake-locking symptoms as would a hole blocked by contamination. So, while you have the master cylinder apart, carefully check to ensure that the bleed hole is fully open when the front brake is not applied.
FeedbackLoop
Q Pierre Fontin asked why some riders put their bikes in neutral when shut ting down ("How to remain neutral," Decem ber). Perhaps at least one reason is MSF train ing. When my wife took an MSF course a while back to get her license, instructors insisted that students 1) use the kill switch to shut off the engine-not the ignition switch or sidestand kill); and 2) always leave the transmission in neutral when shutting off. Failing to follow these instructions led to public chastisement.
I have no idea why they insist on this for any modern streetbike. After the course was done, I insisted that she 1) kill her bike's engine by putting down the sidestand when her bike was in gear, clutch disengaged; and 2) turn off the electronics using the ignition key. My rationale is that twice, I have had my expensive bikes
roll off of their sidestands in neutral and sus tain damage. In one of those instances, I tried to catch the 600 pounds on its way down, and it flipped me to the ground hard near the gas pumps across from the one I was going to use. It was painful and embarrassing for me, not to mention getting a sore shoulder and bearing the expense of fixing the bike's damage. If putting down the sidestand in gear doesn't kill the engine, use the ignition switch.
IMnHO after 46 years of riding, the MSF should revise their training. It can lead to damage, injury and (having seen many riders forget to turn off the ignition after using the kill switch) dead batteries. Kickstand/ignition = 2 simple steps; neutral/kill/kickstand/ignition/reset kill = 5 steps. Listen, MSF: KISS! Mark Bradley Submitted via www.cycleworld.com
Recall Roster
NHTSA Recall No. 12V531 000 Manufacturer: KTM North America, Inc. Model: 2012-2013350 EXC, 350 EXC-F Number of units involved: 1181 Problem: KTM is recalling certain of these motorcycles manufactured from September, 2011, through August, 201 2. Due to the supplier's manufacturing inconsistencies, the fuel system's pre formed hoses, located between the fuel tank and the throttle body fuel rail, may develop cracks or holes at either end, allowing fuel to leak. Fuel may leak onto the rear tire while the motorcycle is being ridden, increasing the risk of a crash. And in the presence of an ignition source, a fire also could possibly occur. Remedy: Dealers will replace the defec tive fuel hoses free of charge. Owners not receiving this remedy can contact KIM at 888/985-6090.
Got a mechanical or technical problem with your beloved ride and can't seem to find workable solutions? Or are you eager to learn about a cer tain aspect of motorcycle design and technolo gy? 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, 15255 Alton Parkway Suite 300, Irvine, CA 92618; 2) e-mail itto CWservice@ cycleworid. corn; or 3) 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 in formation to permit a reasonable diagnosis. Please understand that due to the enormous vol ume of inquiries we receive, we cannot guaran tee a reply to every question.
