Service
SERVICE
Holey Kaw
Paul Dean
I have a 1990 Kawasaki ZX-11. When I ran it up to 140 mph the other day, smoke (a lot of it) started blowing out the exhaust. After that, the motor was backfiring and sputtering. When I finally got the bike back home, it leaked about a handful of oil out one of the drain hoses (not the fuel overflow). I checked the coolant and it was full, yet the bike has lost its power. Two years ago, I had a big-bore kit and a polished crank installed in the engine. What’s your diagnosis? DaZman11 Posted on America Online
It’s my guess that during your 140mph blast, your ZX-11 either holed a piston or suffered a partial piston seizure that has caused the rings on that piston to hang up. In either case, oil is getting into at least one cylinder’s combustion chamber, which explains the smoke billowing out the exhaust; and the blow-by past that damaged piston and/or its rings is causing excess crankcase pressure, forcing oil up through the crankcase breather hose into the airbox. The oil accumulates there, then gradually makes its way out through the drain hose in the bottom of the airbox. And the loss of some or all of the compression in one cylinder would explain the engine ’s reduction in power.
You (or a good shop or mechanic in your area) need to perform a leakdown test or a standard compression check to confirm that the engine has indeed lost compression, and to ascertain which cylinders are at fault. You also need to determine why this problem occurred in the first place. Check for things like an air leak in the affected cylinder’s intake manifold, low float level or insufficient fuel flow in that cylinder’s carb, etc. This diagnosis is of critical importance, because if you cure only the symptoms, the ailment surely will recur.
Kind of a drag
After a 10-year layoff from motorcycling, I purchased a ’98 Honda 750 Ace. I love the bike, but after putting about 3000 miles on it, I’ve decided that it has two shortcomings: power and noise. So, I am considering installing drag pipes and a carb kit. What kind of power gains should I expect, and will the modifications hurt the motor in any way? Mike Pruitt New Salisbury, Indiana
Properly installed, the equipment you are considering will not damage the Ace’s engine. But while the carb kit will sharpen throttle response and improve overall running, the drag pipes are likely to hurt performance more than help it. Drag pipes are little more than two separate pieces of constant-diameter tubing, meaning they can be tuned for optimum performance only in one, often narrow, range of engine speed. The net effect is that the pipes can deliver a horsepower boost in that one rpm range, but do so by yielding less power at all other rpm. And most of the time, that loss of performance seems to occur in the rpm ranges where most people do most of their riding.
We haven’t tested any of the exhaust systems available for the 750 Ace, but our experience with other bikes indicates that the 2-into-l systems made by reputable manufacturers tend to deliver the best all-around performance on VTwin cruisers. But even with those pipes, power gains at some engine speeds may be offset by losses at others. Well, at least they sound good.
Tired old story
Last fall, I bought a new set of Dunlop Elite II 491 tires for my Honda Gold Wing. When removing the bike from storage this spring, I noticed several nasty cracks all around the sidewalls on the front tire only. The bike sat in winter storage with three other bikes-all with older tires, some more than four years old-that did not have this problem. The storage area has only a single, 60-watt lightbulb, no sun can enter, and I never use any tire dressings. I called the dealership where I purchased the tires and they said this is Dunlop’s problem, not theirs, then rudely hung up. I also called a Honda dealer who said this was only a cosmetic problem and not to worry about it. I really depend on my tires and I feel cheated to have to live with this mess. I may just go back to Metzelers.
Wingman07 Posted on America Online
You didn’t get a poorly manufactured front tire; you got an old front tire. The 491 Elite Ils have been on the market for quite a few years, and through bad luck, you ended up with one that has been lying around in someone ’s stock so long that sidewall cracking-inevitable on any tire, given the passage of sufficient time-began shortly after your purchase. So, don 't blame the tire manufacturer; Dunlop makes excellent tires, and this same problem could occur with any tire, regardless of brand.
Still, you have a problem tire and dealer, so I recommend you contact Dunlop ’s motorcycle division by calling 716/639-5397. The people there will not only be interested in hearing > about your trouble with the tire, but with the dealer who sold it to you. I can’t tell you whether or not they 'll replace the tire, but I feel reasonably sure that Dunlop will do something in an attempt to make you a satisfied customer.
Real-steel stoppers
I’ve been considering installing steelbraided brake lines on both my Yamaha RZ350 and Honda Hawk GT. I know that you experts can feel the difference between conventional rubber lines and steel-covered lines, but will the average street rider realize any benefit in braking performance or feel with such an upgrade? And is this a job I can do myself?
Chuck Larson Wautoma, Wisconsin
On both counts, the answer is “yes." You will detect a difference in braking feel, although the degree of improvement you perceive will depend somewhat on your riding style and skill level. And if you’re a half-decent backyard mechanic, you should be able to handle the brake-line swap yourself.
Do understand, however, that in themselves, steel-braided lines do not improve a braking system ’s stopping power; they don 't increase the mechanical advantage between master cylinder and calipers, and neither do they change the coefficient of friction between the pads and rotors. All they do is improve a brake s feel by eliminating the mushiness at the lever that often occurs with plainrubber lines.
No shift, Sherlock
I own a ’93 Honda CBR600F2 that is having problems with second gear. If I run it hard through first gear, like up to 9000 or 10,000 rpm, and shift hard into second, the transmission will almost immediately jump out of second and into neutral. But if I ease through first and gingerly shift to second, everything is fine. Great, except that having to “ease” my way around town sucks; I could have bought a Chevette to do that. It can’t be good for the engine to scream violently up to 12,000 rpm when it jumps out of gear. Will this problem require an entirely new clutch or is wear and tear on the linkage causing it to slip? Please help.
Keith A. Broady Jeffersonville, Indiana
Even though I have replied to similar questions in recent issues, I continue to get a lot of inquiries on the subject, indicating that many people are confused about this type of gearbox problem. As a result, this may be a good opportunity to clear up that confusion.
Keith, the problem with your gearbox is neither in the clutch nor the shift linkage; if it were, it would occur in every> gear-or at least a few other gears-not just second. The same goes for the clutch; it affects everv gearchange in the same way, not just the first-to-second shift. Nope, your CBR 's transmission jumps out of second after a hard, high-rpm upshift because it has either a bent or badly gouged secondgear shift fork, or because the secondgear engagement dogs are battered and worn. In either case, the engine has to be taken out of the frame and disassembled to effect the necessary repairs.
Fins are fine
I have been riding air-cooled motorcycles (mostly Harleys and BMWs) for more than 20 years, and I still don’t understand how any air-cooled engine can dissipate enough heat to withstand stop-and-go traffic. How, for example, can an aircooled engine survive the slow crawl of Bike Week traffic without valve or piston-ring damage? Also, how can 50-to70-weight oil be recommended for Shovelheads but 20-50 is fine for Evos and other modern bikes? It seems to me that excessive head temperatures would damage half the bikes in Daytona each year. Your comments, please.
S. Moffitt
Tampa, Florida
This is a weighty subject worthy of much more space than we have here, but I’ll at least try to touch on the relevant points. For starters, understand that air-cooled engines were-and still are-designed from the get-go around the limitations of their cooling medium. Key design factors such as compression ratio, combustion-chamber shape, camshaft grind, ignition curve, piston-to-cylinder clearance, oilingsystem configuration, carburetor jetting, recommended grades of oil and many other elements all were decided based on, to varying degrees, the efficiency of the cooling system in extreme conditions.
How limiting is air cooling? Well, if any given air-cooled engine were to be converted to liquid-cooling, most of its previous tuning and design parameters could be thrown out the window in favor of others that would greatly enhance performance and reliability.
The point here is, an air-cooled engine doesn’t just happen to have air cooling; it was designed, developed and refined to be air-cooled from the outset, including having its performance limitations established. Overcoming these limitations is why it took Harley-Davidson so long to develop the Twin Cam 88, even though it is similar in basic design to the Evo; this is one of the reasons the 1440cc TC 88 onlv makes 60-some-odd horsepower; this is why manufacturers of high-performance motorcycle engines switched to liquid-cooling a long time ago.
An air-cooled engine therefore can crawl through stop-and-go traffic without meltdown because its state of tune and power output at those speeds keep the cylinder-head temperatures within the range that can be managed by the cooling medium; and because the clearances between critical engine components has been determined by the demands of extreme thermal expansion more than by the needs of performance.
This also explains why a Shovelhead or Panhead requires heavier oil than an Evo or Fathead: heat. Through greater finning area and more sophisticated head design, the newer engines dissipate heat much more efficiently, allowing use of lighter multi-grade oil.
Slip-ons for Kats
I currently own a ’94 Suzuki Katana 600 and I am interested in increasing its horsepower and making this baby sound like a real sportbike. Keeping in mind that money doesn’t grow on trees, are there any slip-on performance pipes available for my bike? I’ve checked almost everywhere but no one seems to have one. Power Hungry
Chicago, Illinois
To my knowledge, the only slip-ons currently available for your Katana 600 are the FIR and FIS, two reasonably priced series of mufflers made by Cobra. Their manufacturer makes no claims about horsepower increases, however, and we’ve never tested them, so I can’t tell you what they 'll do for your Katana ’s performance. I suspect they won’t do much besides alter the sound and cut a few pounds off the bike ’s overall weight.
Stained & tuned
During a recent ride in San Francisco,
I saw a parked ’93 Honda VFR750 that had an Australian exhaust system called “Stantone.” Can you help me find some information about this exhaust system? Rfox369
Posted on America Online
Actually, the exhaust system in question is called “Staintune.” The name is embossed on the muffler in stylized type that is hard to decipher if you don’t already know what it says. The Staintune is a beautifully made, stainless-steel (hence, the first part of its name) system that works and fits nicely, but is pricey. If you want to know more, you can contact Staintune’s U.S. distributor, CRT Imports in Mountain View, California, by calling 800/782-4686, or visiting its website at www.cbtimports.com. □
