Service

SERVICE

JOE MINTON

Dead Turbo

I recently bought a crashed 1984 Kawasaki GPz750 Turbo. After repairing just about everything, I still have a charging problem with the electrical system. I replaced the original crash-damaged stator with a used unit. The bike started up fine, ran for awhile, but I soon had to resort to push-starting, and then it went dead altogether. What should I do next?

J.R. Morgan Rowlett, Texas

You 've run smack-dab into one of the difficulties of fixing-up an old motorcycle. As I noted in April's "Keepers" article, when shopping for a used bike, there's a fine line between a bargain and a burden. Your problem should be fairly easy to track down, though, and may be as simple as a worn-out battery. More than likely, however, you will need to troubleshoot the entire charging system. This will include testing the recti fier I regulator, the stator and all the wiring that connects these components. You'll need a volt I ohm meter and a shop manual. The test procedures are simple. but if you do not have the equipment or the experience, find someone who does and have them do the testing.

Clutch questions

Over the past five years. I've put 30,000 miles on my Suzuki GSXR750, and I've come up with a few questions. What are the advantages/ disadvantages of 1 ) hydraulic vs. cable-actuated clutches: and 2) wet vs. dry clutches.

Kerry Ogata San Diego, California

Good questions. Hydraulic clutches, like disc brakes, are self adjusting, and therefore have a consistent feel. Field experience has also shown that hydraulic dutches require less maintenance than cable-operated clutches. About the only thing you 'll need to do is change the fluid every so often—/ recommend two-year intervals.

In the past, before the advent of improved dutch material, dry dutches were used—especially in racing applications—because they ran cooler than wet dutches. The main advantage, today, of a dry clutch is cleanliness. The typical wet clutch—as used in most Japanese bike engines—runs in the engine's oil. Normally, this is okay. In fad, most wet dutches today are virtually indestructible. However, anytime the clutch is abused, such as in a dragor roadracing start, abrasive particles front the clutch plates will be dumped into the engine oil. Those particles can gel into critical moving parts. Drag racers are familiar with piston scuffing due to dutch-plate particles. A dry clutch is isolated front the engine oil and therefore cannot contaminate it.

Wheel right

I have a 1990 Honda CBR 1000 that has developed a pair of hairline cracks in the middle of one of the rear-wheel spokes. A mechanic at the dealership where 1 purchased the bike said there is nothing to worry about, because it is only the paint that has cracked. This may be true, but I would feel much better if 1 knew for sure.

Is this a common occurrence on this type of wheel, and how can I determine if it is safe to use?

Dave Pisak Hazel ton, Pennsylvania

We've checked with Honda, which reports no problems with wheel cracking on the CBR / 000. But do not ride your bike, even around the block, until the crack has been properly inspected. With all due respect to the mechanic you consulted, unless he is Supermatt and has X-ray vision. he cannot determine the nature of your wheel's crack with his eves. Contact vour Honda dealer again and tell him that you are concerned about your safety. Gel Honda to look at the wheel. And. again, don't ride your bike until that has been done.

All manufacturers design a safety factor into their parts. After they have determined, to the best of their ability. what maximum loads a part must endure, engineers add strength to the design to ensure reliability. Ibis safety factor varies with the application. Compressed-air tanks, for example, must withstand four limes their maximum rated working pressure without bursting. On a helicopter, where light weight is necessary if it's to gel off the ground, parts may be only !.2 times as strong as the maximum loads envisioned. One of the reasons Formida I race cars frequently break is that their components are designed with minimal safety factors in the interest of inc rea sed perforo nine e.

A crack, particularly a crack in a cast-aluminum part. lays waste to the engineers' carefully designed-in safety margins. A crack in a cyclically stressed part, like a cast-aluminum motorcycle wheel going down the road, can quickly lengthen and cause the part to suddenly and completely fail.

Ascot aid

The “strange, rattling noise" that afflicts letter-writer Donald McLaughlin’s Honda Ascot 500 (see “Comfort and clues," Service. June,

1 99 1 ) is very common. My Ascot, as well as those of my nephew’s and a friend’s, suffered the same thing.

The Ascot has an inner exhaust pipe welded inside the header pipe. On all of our bikes, the welds had cracked, letting the inner pipes rattle around. Here's the cheap fix. Remove the pipe. You will be able to see the broken inner pipe. Cut a hole in the outer pipe about a quarterinch down from the exhaust flange. Do this on the back of the pipe, where it won't show. Then take the pipe to a welder and have him reweld the inner pipe to the outer one. Weld the hole closed. Presto, that strange noise will disappear.

Cal Drake Frazee, Minnesota