Investigation of Repair
on short-circuited Alternator
of Suzuki GS 400

sachverstand2, holgi, alex, udo, marco, rudi et al.,
Center of Investigation on Antique Japanese Motorcycles,
Gymnasio of Technical Sciences,
Offenbach am Main, Germany
mailto: sachverstand2 @ web.de

29. August 2006

Inhalt

• Inhalt
• 1. Abstract
• 2. Symptoms
• 3. Searching the faulty module
• 4. Removal of the Alternator
• 5. Try 1: Use of pvc-isolated unflexible cable
• 6. Try2: Painted cable and insulating tape
• 7. Try3: As Try2, but with liquid polystryrol
• 8. Try 4: pvc-isolated cable, protected by polystyrol and glass canvas
• 9. Conclusion

1. Abstract

We present this paper to the www community in the hope that it will be useful, but without tolerating refuse to assimilation of the basic principles of motorbike alternators.

2. Symptoms

3. Searching the faulty module

• Malfunction of the permanent magnets (located at the left end of the crank);
• loose or lost magnets, occasionally destroying alternators, starter mechanisms, and immobilizing the crank;
• poor connection or absence of rectifier, regulator, or air cleaner box;
• corroded, relaxed, bent, or torn connections in the cable tree;
• poor or extreme poor function of switches or cable connections;
• worn battery with no electrolytic condensator (200 uFarad, 50 V) over it;
• blown fuse.

As all these parts had been revised, maintained, stretched and/or replaced before, assumptions have been made about means of investigation of the alternator without removing it from the motorcycle.

To accomplish this, the three cables from the alternator to the rectifier were disconnected after removal of the left side cover of the bike, and an ohmmeter was attached to measure the resistance from each of the cables to the bike's ground.

As all of them proved to be less than 1 Ohm, whilst values greater than 100 kOhm had been verified as o.k., the alternator and/or its cables were found to be the most defective part.

4. Removal of the Alternator

After finding the coil with 0 OHM resistance to the body of the alternator, we cut through the singlecoils of this coil one after another, and did not find the broken one, until there were only 6 singlecoils were left to provide electric power to the motorcycle.

As an electric machine cut down to half would surely be overloaded and thus be unreliable in daily traffic, especially if a 60W halogen lamp is ON all the time when driving in Germany, we decided to remove the coils completely and to build something new, easy, more reliable than the original instead of messing around with original Japanese circuitry of 27 years of age.

5. Try 1: Use of pvc-isolated unflexible cable

12 turns of this were attached to each of the teeth of the alternator. Whilst the original number of turns, as removed from the bike, was 52, this proved to be the maximum possible count of turns because the isolation was so thick. See the picture.

Abbildung: Try 1: pvc-isolated cable from the nearby station

The alternator was mounted, then, connected to the motorcycles electric circuitry, and tested on an overland trip to the Spessart. The trip included 30kms of autobahn and some curve-spangled slopes, 5km the longest.

The alternator survived 120 km before suffering another short. This was noticed because the headlamp (60 Watts) was actuated all the time, and the motorcycle engine ceased firing whilst cornering with the flashers engaged. With the headlamp switched off, the test engineer succeeded to come back to the workshop.

In the workshop, the alternator was removed again. We found that all the pvc had gone except some black debris that still hung around under some wires. We had used no black pvc cable so the blackening effect must have taken place while the alternator in the hot, vibrating, oil-splashing, unlighted engine was kind of being cooked.

With the isolation destroying itself, it was obviously pointless to perform another try on this.

6. Try2: Painted cable and insulating tape

So, we provided each tooth with a double layer of insulating tape, and 30 layers (homespun order) of two-layered painted cable of 0.8mm diameter. See the pictures.

Abbildung: Try 2: Double layer of insulating tape

Abbildung: Try 2: The first coil is attached

This arrangement was mounted to the motorcycle and survived 75km of autobahn and mountain drive. The test engineer switched off the lights and managed to come back to the workshop.

Abbildung: Try 2: Detailed view of the central soldering point

After removing the alternator from the machine we found that the wires had lost their order and, in spite of efforts to keep the turnings tight and reliable, had lost their positions, this way vibrating, rattling and scrambling all together and beating the insulation locally into an inoperable state. The isolation of the wire had mostly gone, with the wire shining copper-colored on 74.2% of its surface, while the other 26.8% remained black and consisted of easy-to-remove, burnt debris of what had former been two-layer painted isolation.

The textile reinforced insulating tape had changed its color from yellow to black. It appeared to have been cooked, lost all ist smoothness and was breaking like glass when it was removed from the teeth by cutting it down with a sharp swiss army knife.

The central soldering point had un-soldered itself. No solder was found near the alternator, so we think that it lurks still somewhere in the engine.

7. Try3: As Try2, but with liquid polystryrol

Honestly spoken, the only substances to be known as to withstand these raging environmental conditions were metal and rubber. Metal was not practical, as it does not insulate a bit, and rubber in vulcanizable form was not at hand. Another duroplast, known to be very adhesive and widely used for fixing car bodies, thus resistant to vibrations and casual splashes of oil and heat, is liquid polystyrol.

We repeated, as shown in Try2, and added a sparse amount of polystyrol, mixed with catalysator (often called ''hardener''), to each tooth.

There are no pictures here. The results were far worse than expected: after 15km of flat countryside drive, the system broke, and the test engineer drove back to the workshop without lights and flashers, using half of the battery for firing alone.

There was some black debris left of the polystyrol. Actually, it did not seem to withstand the temperatures of the engine at all.

8. Try 4: pvc-isolated cable, protected by polystyrol and glass canvas

Our investigations so far had pointed out that re-wiring an alternator was no easy job, as the wires had to withstand great forces of many kinds for long periods of time.

After some hours of thinking we discovered that a good isolator of high temperature resistance and great mechanical durability had been delivered in the polystyrol box as well: some glass canvas. Before giving up this project, we used it all, and the remaining polystyrol, to build Try4.

First, we puit 2 layers of double folded glass canvas around each tooth. Two strips, 3cm wide and 80cm resp. 20cm long, served for this purpose, thus minimizing the risk of contact between wire and alternator body. See the picture.

Abbildung: Try 4: Insulating double glass canvas layer

As we had run out of double painted wire, the test engineer walked again to the nearby station and collected another bunch of mid-70ies, colored, pvc-isolated, unflexible wire, which was attached and soldered as in Try1. We found that because of the thickness of the glass canvas layer there could be reached only eight turns around each tooth, instead of the original fifty-two. In this condition, the alternator could operate sufficiently at high rpms only, if ever, but the priorities had been changed by the foregoing Try1 - Try3.

Abbildung: Try 4: wired with unflexible pvc-isolated cable, soldered

After the wire, we attached another 2 layers glass canvas per tooth and then added gentle amounts of polystyrol to each tooth with a teaspoon. There was no need to be economic with the polystyrol, as protruding floats and corners could easily be removed with a screwdriver and a swiss army knife. Polystyrol which had creeped into the mounting holes was removed by turning a screw some turns in and then violently blasting the screw and the polystyrolic remains with a hammer out by the other side.

The alternator was mounted to the motorcycle, and our test engineer drove a 500km journey, by fields, forests and curve-spangled mountain roads without failure. Actually, the test engineer went to a dealer for second-hand Japanese motorcycle parts who lived 250kms away, near Nördlingen, and bought a second-hand alternator which looked like new. On this trip, the alternator did not fail, and with the headlamp on, the voltage was sufficient at more than 4500 rpms, where 5000 to 6000 rpms is a usual range for going cross-country with a GS 400. In town you would use less to avoid nasty questions by the police.

Having bought the ''new'' alternator, and having brought it back to the Center of Investigation on Antique Japanese Motorcycles, Try4 was removed from the engine - and looked like new.

The polystyrol was fully intact, without any cracks, and through the outer glass canvas shield, which had become transparent with the gentle amounts of polystyrol soaking into it, the original colors of the original 1970ies pvc-isolated station cable shone through, unburnt, unvibrated, ready to take another trip, this time for some 1,000 kms.

9. Conclusion

Abbildung: Try 4: sealed with glass canvas and gentle amounts of polystyrol, ready to go for a 500 km test drive

In this report, we analysed the typical failure procedures of alternators of antique Japanese motorcycles, covered some insufficient repair experiments, and documented the results.

We finally found that a collection of widely available materials, ingeniously composed on a standard workbench, would withstand the loads of electric circuitry, built into a motorcycle engine and loaded with approx. 15 Ampere.

Further investigation is needed to assure the high quality of the circuitry. We propose a 100,000km trip with the repaired alternator, going through hot and cold climate, mountains and plains, on high-speed tracks and curve-spangled heights. A trip around the world would surely suffice, assured that the distances where the motorbike would be carried by ferry, plane or driver are strongly kept short.

However, we doubt that the presented motorcycle and its driver, with its 150,000km frame, its 80,000km engine and his 100,000km sitting organ, would withstand the loads of such an experiment.

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