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Aprilia Futura – Charging system problems
The charging system on the Aprilia RST 1000 Futura has been shown to be suspect on some bikes, especially when running accessories and/or an alarm.
That said, the problem is probably not as extreme as on Honda VFRs, and is easily solved, providing things haven’t gone too far.
The system works like this: The alternator generates alternating current from the engine, then sends it to the regulator/rectifier, which turns it into Direct Current at a steady rate to run the bike’s electrics and charge the battery.
The alternator is rated at 420W*, however, the regulator/rectifier is weak, so charging actually drops the more you rev the bike. Especially if you want to run accessories or an alarm, this can lead to a whole range of problems, from starting difficulties to melting brown connectors to failing starter solenoids and even total failure of the regulator/rectifier.
To find out whether your bike has a problem, you need to test the charging voltage by running a multimeter across the battery terminals with the bike running. Doing this with the ignition off is pointless as it only tests the battery voltage.
You need to test the battery voltage at tickover and again at 4,000rpm. Stock Futuras will show a drop in voltage as the revs increase.
Ideally, you are aiming for a voltage of 14 to 14.5 volts at 4,000rpm. A higher charge rate could indicate a problem with the regulator/rectifier.
To fix this issue, see the Wiring Mod page.
Also see the generator page
* Aprilia’s own specifications for the Futura list the output at 470W, but spare parts are listed at the lower wattage. The specs could just be a misprint.