Suzuki builds a great motorcycle but one weak point in many models is that the charging system is underpowered and the voltage regulator / rectifier (VR/R) is prone to early failure.
With only a few exceptions (the Honda GL1800 and ST1300 are two) Japanese motorcycles utilize a simple and compact charging system with an oil immersed AC generator (wirewound stator and permanent magnet rotor) driven off the end of the crankshaft and a solid state, "total loss" voltage regulator / rectifier.
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Although these systems are physically different from model to model they're almost always the same functionally. The 3-phase AC output of the generator is sent directly to the voltage regulator / rectifier. One function of this unit is to covert (rectify) the alternating current (AC) output of the generator into direct currect (DC) used by the bikes electrical and electronic components. Each of the three output leads has a set of diodes (one-way gate) to accomplish this. |
The other function is to limit the voltage output of the charging system to the range usable by the bike's electrical components and to recharge the battery. That range is 12.6 to 14.5 volts. Lower voltages won't keep the battery charged and higher voltages will damage the elecrical and/or electronic components. The generator uses permanent magnets in the crankshaft driven rotor and non-excited stationary field windings. It's really just a sophisicated version of the experiment you probably performed in middle school science lab with a spinning magnet and a spool of wire. The voltage produced by the generator is more or less directly related to the engine RPMs and will increase up to around 70 volts AC. The charging system is designed to provide enough power to charge the battery and operate the electrical components plus provide a little (a very little with Suzukis) extra to run accessories and add-ons. So, most of the time there is excess capacity and the voltage regulator portion of the VR/R unit shunts this excess current to ground. In other words, it simply (and somewhat crudely) wastes the unused capacity as heat... a lot of heat. And, IMO, that is why they usually fail- heat stress.
Manufacturers reduce cost by limiting the size / capacity of the VR/R to the minimum required for a given bike. In the case of the Gen 1 Suzuki SV650 (and lots of others), I believe they were a bit over-zealous in their cost reduction effort. The good news is that these units are electrically compatible across a wide range of makes and models. In fact, all the ones I've seen were contract built by Shindergen Electronics for the motorcycle manufacturer (Honda, Suzuki, Kawasaki and Yamaha). So, it's possible to fit a larger, higher capacity unit from a larger bike to the SV. Be aware that such an upgrade will NOT provide more power for electrical accessories since the available power is limited by the output of the generator. What it will do is substitute a VR/R unit with more reserve capacity and potentially higher reliability and longer life.
My wife and I are on our second Gen 1 SV. Both bikes experienced VR/R failures at about 30K miles. In our case the failures were identical. The unit simply stopped charging the battery. Another friend suffered more serious failure on his Gen 1. When his regulator failed it sent uncontrolled (high voltage) current into the bikes electrical system frying his ignition module, all his instruments and battery. It was VERY expensive. Believe me, you want yours to fail in the first mode rather than the second! The VR/R on the Gen 1 SV is under the right tailpiece so it doesn't get much airflow and I think this factor combined with the fact they are undersized contributes to their early demise. So, IMO, if you have a Gen 1 SV and haven't had a VR/R failure it's just a matter of time.
The Suzuki VR/R costs about $130 and if you buy a new one you still have the same underpowered unit. So, my solution is substitute a used higher capacity unit from a larger and newer bike.
When the first one failed I happened to have on hand a somewhat larger VR/R from an '05 Honda CBR600RR. It was a 7-wire model whereas the SV unit was a 5-wire model. No problem - the extra two wires are just redundant output leads so one only needs to tie the positives and negatives together to convert to 5 wires. I simply cut the connectors from the failed Suzuki unit and soldered them on the leads from the Honda unit. It worked great for another 10K miles and when I sold the bike it was still going strong.
For the second replacement I watched eBay for few days and was able to buy a VR/R unit from a '04 CBR1000RR for $13.50 delivered. Now that was a deal! The higher capacity is obvious in that the unit is not only substantially larger than the OEM Suzuki unit but the leads were 1 or 2 wire guages larger too. This was a 5-wire unit so replacing the Honda connectors with those from the Suzuki unit was a piece of cake.
The three yellow wires from the generator have no polarity. They carry the alternating current from the generator and they all go to a set of dedicated diodes, so it doesn't matter which ones you solder to. However it's essential that the output wires be properly polarized. The Suzuki positive is the red wire and the universal Suzuki ground is black with a white stripe. If you have a wiring diagram for the donor bike you can easily determine which output wire is positive. But, since I didn't have one for the CBR1000RR, I had to identify the polarity experimentially. To do so I soldered the input connector onto the yellow wires then plugged it in and started the bike. Using my voltmeter I determined that the red wire is the positive and the green one is ground on the Honda unit. So, I connected the Suzuki output connector appropriately.
Some pictures follow. BTW, I apologize for the soft focus. I couldn't tell that I was too close on the camera viewfinder but it's obvious in the enlarged pictures.
OK, so how does it work? In a word, great. At idle the charging voltage is steady 13.5 and when revved up to 3K RPM the voltage stablizes at 13.8. PERFECT! As mentioned above I don't have any more electrical power but the Honda VR/R unit is so much larger than the OEM unit, I doubt that I'll ever even stress it.