Service
SERVICE
Paul Dean
Taking a stand
I ride a BMW R1100RS and my husband rides a Honda CBR1000F. He is religious about putting his bike on the centerstand, even during short stops, while I leave mine on the sidestand for days at a time. I can get my bike on its centerstand without help, but it can be a challenge. I usually ride at least once a week. Is there any reason why a bike should not sit on the side-stand for extended periods of time?
Monika Schultz Houston, Texas
Leaving a bike on its sidestand generally presents no problems. After all, most sportbikes-along with off-road motorcycles, dual-purpose bikes and all Harley-Davidsons-don 't even have center stands. In today’s litigious society, if the manufacturers thought for a minute that sidestands were going to cause any problems, they d either stop equipping new bikes with them or strongly advise against their use. A few motorcycles do, however, have the potential for minor hassles if parked on their sidestands-particularIv BMW’s inline-Triples, inline-Fours and Boxer Twins, as well as Honda Gold Wings, all of which have trans-
verse, horizontal cylinders. When such a bike is leaned over onto its sidestand, the left-side cylinders are angled downward, thereby placing the combustion chambers lower than the crankcase. If the bike is left in that position for very long, a small amount of oil can run downhill along the bottom of the cylinder walls, make its way past the piston rings, and enter the combustion chambers, where it is then burned and turned into exhaust smoke when the engine is restarted.
This condition has been problematic with some K-model BMWs, but not with Gold Wings or BMW Boxers. And it’s certainly not a concern for motorcycles with vertical or near-vertical cylinders such as the CBR1000F.
On the other hand, when parking a bike for months on end, as you might when storing it for the winter in cold climates, putting it on the centerstand has its advantages, particularly if you prop the bike in a way that keeps both tires off the ground. This prevents any chance of permanent flat-spotting or uneven deterioration of the tires.
There also are everyday situations in which a centerstand is preferable to a sidestand. Sometimes, a sidestand does not allow a bike to lean far enough to the left to prevent it from falling to the right-such as when parking at the right side of crowned streets and roads-whereas the centerstand will hold the bike much more securely. And when parking on soft ground or pavement, sidestands can sink into the surface far enough to let the bike fall over. But a centerstand distributes the weight over hw footprints rather than one, which reduces the likelihood of the bike toppling over.
Vulcan muffler meld
I am completely satisfied with my 1985 Kawasaki Vulcan 700, save for one thing: the stock exhaust system is scratched and worn. I want to replace it, but I can’t find what I want. There are lots of exhaust components available in the aftermarket to fit the Vulcan, but they all change the exhaust from one pipe per side to a staggereddual system on the right side, to give the “Harley look.” I’ve seen these systems on other Vulcans and I don’t like the look at all. I want a system that keeps one pipe on each side of the bike, with tapered or slash-cut mufflers. The local cycle shops claim no one makes such a system and that I’d have to have one custom-built. Tell me this isn’t so. Phil Campbell
Lewiston, Idaho
This isn’t so. Cobra Engineering (4760 E. Bryson St., Anaheim, CA 92807; 714/779-7798) sells slip-on mufflers that fit the Vulcan 's stock heacipipes and thus keep the original two-sided exhaust-system layout. The mufflers are available either in slashcut or fishtail tip styles.
Fuel crisis
1 recently bought a 1983 Kawasaki GPz750 in fantastic condition. It only has 3800 original-owner miles on it and was garage-kept. It runs beautifully, almost like new, I suspect, except that it can be almost impossible to start after it sits unused for a long period. If I start it every week or so, there’s no problem. But if it hasn’t been run in a month or so, it often is a real bear to get running. It usually tries to fire off as soon as the starter button is pushed, but then all signs of combustion disappear until either the thing suddenly comes to life or else the battery goes dead. Then, strangely enough, after a battery charge, it usually fires right up. Once the engine is running, it performs perfectly. What goes here? Dean Keith
Elmhurst, Illinois
Given the small amount of diagnostic information you 've provided, my suggested solution is simple: Turn the fuel petcock on the gas tank to Prime before attempting to start the engine.
Your GPz has a vacuum-operated petcock, meaning that it contains an automatic shutoff valve controlled by a diaphragm connected via a rubber hose to the intake manifold. When the engine is running, intake-manifold vacuum pulls the diaphragm open, allowing fuel to flow into the float bowls. When the engine is off, a spring holds the diaphragm closed, preventing the flow of fuel. This action occurs with the petcock in either the On or Reserve position. It also explains why a vacuum petcock usually does not require an Off position.
When your bike sits for a long time, all or most of the fuel evaporates from the float bowls. Then, when you try to start the engine, there is not quite enough steady manifold vacuum at cranking speeds to hold the diaphragm fully open. It therefore can take a long time for all four float bowls to fill-enough time, in fact, to run down the battery. But if you turn the petcock to Prime and give it 30 seconds or so to fill the float bowls, the engine should start right up.
Follow the arrow
On pages 45 and 46 in your January, 1994, issue, the pictures of Team Yoshimura’s GSX-R750 Supersport racebike show the front tire mounted backward. Has Yoshimura developed a reverse-mounting strategy for that sticky Dunlop Sportmax GP on the front? I happen to ride with the same D364 front/Sportmax GP rear combination on my ’91 GSX-R750, but my front hoop is mounted so that the arrow on the sidewall points in the direction of rotation, which is opposite to that on the Yosh bike. Any insight?
Corey Ray Bump Ava, Illinois
The front tire on the Yoshimura 750 is indeed mounted backward. But for roadracing, it really doesn't matter. The Sportmax GP ’s tread pattern is directional only in terms of how effectively it prevents hydroplaning on wet surfaces. On a dry racetrack, the direction of the tread has inconsequential effect on the amount of grip, so the tire can be mounted either way
If most or all of your riding is on the street, however, you should simply mount the front tire-and the rear, as well-according to the arrows on the sidewalls. This will allow the tread to provide the best water drainage when you ’re riding in the rain.
Under certain rare and extreme circumstances, mounting a tire backwards can result in tread damage. During a tire ’s manufacture, the tread is installed onto the carcass in a single strip that is vulcanized in place, with the ends of the strip butted together by an overlap joint. Like one of those Chinese finger puzzles, the overlap joint is directional: If twisted in one direction it tightens, and if twisted in the other it loosens. Consequently, any tire’s recommended direction of rotation is determined so that the strongest forces acting on the tire-braking on the front tire and acceleration at the rear-will be tightening the overlap joint, not loosening it.
Dunlop ’s technical advisor, Jim Allen, claims he has only rarely seen a tire tread separate at the overlap joint because of backward installation. But those cases always involved a bias-plv tire, always occurred on the racetrack, always involved the rear tire of a powerful racebike, and only happened when the tread had worn down almost entirely.
