Service
SERVICE
Paul Dean
Power to the pieces
I own a 1986 Honda VFR750 and would like to install some additional accessories in the electrical system, such as a radar detector, extra running lights and an electric vest. How do I know when I’m overloading the system? Is there an easy way to tell how much extra juice any given bike can put out? Ron Broder Cleveland, Ohio
There are a couple of ways to determine if a charging system can cope with additional electrical accessories. You can do it mathematically if you know the alternator or generator output and the amount of current each stock electrical component draws, as well as the wattage rating of each additional accessory you install. Ratings of stock components are often found in owner's manuals or shop manuals, and electrical accessories usually have their ratings either listed on the devices themselves or mentioned somewhere on or in their packaging. If a component is rated in amperes instead of watts, simply multiply the number of amps by the battery voltage to calculate its wattage. A 12-volt accessory with a 3-amp rating, for
instance, draws 36 watts. You then add the wattage of all the electrical components that you might ever have in use simultaneously. If that total does not exceed the generator output, the charging system should be able to handle the added load.
On your VFR. the AC generator has an output of 300 watts at 5000 rpm. The headlight draws 60 watts on high beam, 45 on low beam; the taillight uses 8 watts, the brakelight 27 watts; the two front running lights each pull 8 watts, while each turnsignal filament draws 27; the ignition system requires 12 watts, the fuel pump about 20 watts. So, if your VFR is running at or above 5000 rpm with the headlight on high beam and you hit the brakes while the turnsignals are flashing, the total current draw will be just under 200 watts, leaving 100 in reserve. That’s enough to power an electric vest, additional running lights and a radar detector (which draws only a minuscule amount of current).
If you think that having just 100 watts to play with is cutting it a little close, remember that when the brakelight and turnsignals are not in use (they're activated only infrequently and briefly), and with the headlight on low beam, the total current draw is dramatically reduced to less than 100 watts. That leaves more than 200 watts in reserve, which is plenty to handle your access or ies-given, of course, that you don 't spend all of your time riding well below 5000 rpm where generator output is less than optimum.
You also can evaluate a charging system ’s ability to meet the increased demand by actually measuring the charging rate with the accessories installed. Start the engine and, while it is idling, disconnect the ground cable from the battery and connect an ammeter between the cable and the negative battery terminal. Then, turn on everything-the stock components and all add-on accessories-and rev the engine. If the meter doesn 't register some kind of a charge by the time the revs reach 2000, and if the charge rate does not reach at least 1 ampere by 5000 rpm, your charging system is overloaded.
Softening the blows
I recently purchased a used, 1989 Kawasaki Ninja ZX-7. The bike has proven to be everything I expected of it-plenty of midrange, razor-sharp handling, excellent brakes-but the suspension sucks. The dealer told me that the bike was engineered for a firm ride, but this is ridiculous. What are my options here? I’ve spoken with Progressive Suspension, but they don’t make a rear shock for this bike. Is the White Bros. $600 rear shock worth the money or do I have other choices? John St. Germain New London, Connecticut
/ have no hands-on experience with the WP icar shock sold by White Bros, for the ZX-7, so I can't honestly tell you whether or not it's worth the money. 1 can tell you, however, that the WP shock is a ve/y high-quality’ unit, but it's tuned primarily for roadracing; so, while it would probably somewhat smooth your ZX-7's ride on the street, the improvement may not he great enough to justify the shock s considerable expense.
Perhaps your best alternative would be to read “ZX-7 Upgrade" in the March, 1993, issue of Cycle World. This is a project-bike report in which we made considerable improvements in the ride quality of a '93 ZX-7. That bike also had a harsh ride, even though it started life with a better suspension than your '89 model. We sent the fork and the shock to Stig Pettersen at Pettersen Pro Suspension (817 Lakeview Ave., Unit B, Placentia, CA 926)70; 714/970-2423) for revolving and the installation of a 12percent lighter shock spring from Fox Racing. The results were quite good for overall street riding, especially considering that the cost of Pettersen 's fork and shock modifications was only about half that of a new shock.
Magic mystery oil
I own a 1981 Kawasaki KZI 100 and have enjoyed years of dependable riding on it. The bike currently has 38,000 miles logged and has been cared for meticulously. Its only problem is excessive oil consumption: It goes through about a quart every thousand miles. It runs very strongly, does not emit smoke, and has normal (150 psi) cylinder compression. It never fouls plugs and doesn't leak. Do you have an opinion about the source of the oil consumption? Craig Rogers Derry, Hew Hampshire
Finding the cause is a matter of logical deduction. If the oil is not leaking out of the engine, then it must be getting into the combustion chambers and being burned. If the compression is up around the 150-psi level, the oil is not getting into the cylinders past the piston rings. The only reasonable conclusion, therefore, is that oil is entering the combustion chambers via its only other logical access route: the valve seals. Each valve has a small seal around its stem, just atop its valve guide, and even a small amount of leakage past these seals can account for the level of oil consumption you are experiencing. A rate of one quart per thousand miles is a bit excessive, but it's not enough to create much visible exhaust smoke, especially if all four cylinders are culprits.
If you or your mechanic decide to replace the valve seals, also check the valve guides for wear. When the valveto-guide clearance becomes excessive, the valves often can wobble around inside the guides enough to either create or accelerate valve-seal leakage.
Kawasaki specifies that the maximum allowable clearance between valve guide and valve stem is .007-inch. You can determine the clearance by using a micrometer to measure each valve stem 's outside diameter, and using a small, inside micrometer to measure the corresponding valve guide's inside diameter. Subtract the smaller measurement from the bigger one to get the valve-to-guide clearance.
License to dive
I own a 1984 Kawasaki 900 Ninja and I don’t like the “AVDS” anti-dive system. I’m afraid I may end up on my head because of it. I’m wondering if there is some way I can get rid of the system without otherwise affecting the fork’s performance. I think anti-dive is not a good thing because it doesn’t allow braking to put as much of the bike's weight on the front wheel like it should for more traction. If you know of a way to eliminate the AVDS, I would appreciate hearing about it. Steve Malouin Sept-Isles, Canada
Riders accustomed to traditional front-fork behavior tend to use frontend dive as a rough indicator of braking force. By eliminating most or all braking-induced fork compression, however, an anti-dive system gives the rider the impression that considerably less weight is being transferred onto the front wheel and that, as a consequence, not as much braking force is at work. In truth, though, the actual amounts of weight transfer, front-tire traction and braking force are virtually the same with either type of fork. So, if you end up on your head during a braking maneuver, it probably won't be the fault of your Ninja ’s anti-dive.
Anti-dive gained popularity during the Eighties because it purported to eliminate-or at least minimize-the sudden quickening of the steering geometry that occurs when the front suspension compresses during hard braking. The speeded-up geometry made a bike much more nervous and twitchy at a time when it needed to be stable and predictable. Anti-dive front suspensions largely cured that problem, but they also brought their own shortcomings, not the least of which was their inability to cope with bumps and other road-surface undulations during hard braking. Anti-dive eventually was dropped as suspensions and tires became more sophisticated and offered designers other ways to keep motorcycles stable when braking.
If you still want to eliminate the anti-dive on your Ninja, a quick-anddirty-but cheap-and-effective-fix can be made by simply crimping closed the metal hydraulic line that runs between the brake-line junction on the rear of each fork leg and the anti-dive housing on the lower front of each leg. This will prevent brake-line pressure from activating the anti-dive mechanism.
A much neater, cleaner method is to remove all the anti-dive hardware altogether. You 'll have to fabricate a couple of sturdy metal plates and matching gaskets to seal the large openings in the fork legs that will result from the removal of the anti-dive housings and their affiliated components. And after you remove the metal anti-dive hydraulic brake lines, you can either seal the holes in the junction blocks with threaded plugs or remove the blocks entirely and replace each stock two-piece main brake line with a one-piece replacement from an aftermarket source such as Russell.
Incidentally, the initials "AVDS" have nothing to do with your Ninja ’s anti-dive system. They are an acronym for Automatic Variable Damping System, which is Kawasaki’s patented fork-damper design that provides added compression damping as the fork nears the bottom of its stroke and/or the speed of fork compression increases. The AVDS stickers just happen to be located near the antidive housings on the lower fork legs, leading many people to the erroneous conclusion that the name refers to the anti-dive system.
