Question about 2005 Gilera Runner VX 125

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1996 piaggio hexagon, battery not receiving charge from engine, indicators and lights go funny with revs, is it the rectifier, the battery was brand new (gel type) fully charged about three weeks ago, bike runs ok.please help.

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Find the reg/rect. check the AC voltage going in, should be about 18-26v & 3000RPM. If you have voltage check the out put Red and frame should be above battery voltage.If not turn off engine and check voltage at reg/rect Red wire (+) and Black(-) if fitted could be conected through body to frame..It should be at battery voltage.if not check for burnt or dirty conectors on the red lead and or the black lead if fitted or the mounting bolt for the reg/rect.
If you have battery voltage and AC voltage at the reg/rect suspect the reg/rect. some units have an extra wire that can be an ignition feed that has power on it when the key is on, but sure these dont have it.

If you dont have AC voltage check the (usualy) yellow wire some can have 1 or 2 wires. If it has 2 wire check voltage across both, if it only has one check yellow and the frame.

Posted on Sep 18, 2010


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When you engage the starter, this is the biggest power draw there is from the battery, causing the light to dim even more.

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Hi, did you charge the battery before use? Is the battery maintenance free or top up type as both need to be charged before using for the first time. Take battery out of bike (make sure you remove the negative lead first) and charge at no more than 1 amp for as long as possible. When charging is completed refit the battery (make sure you refit the positive lead first). You then need to make sure the battery is being charged by the alternator/rectifier circuits. Start the bike connect a volt meter set to DC (use a range of more than 20 volts) across the battery (make sure red lead goes to positive). The reading you get should be at least 12.5 volts, start engine and increase the revs slowly and you should see a rise in voltage to about 14.4 volts. Decrease revs slowly and watch the meter it should either remain near or above 14 volts or drop to about 13.5 in either case your bike is working OK. Hope this helps.

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Check the charging voltage of your battery. It should be about 14.5 volts DC with the engine at twice idle revs. If it is higher than this, you will need a new regulator. if the voltage is in AC you need a new rectifier and battery. The reason the lights dim is due to insufficient current being available to run the lights and the engine at the same time, an indication that the battery is not holding a charge.

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1 Answer

1996 Piaggio Hexagon not charging

Hi, Bumgrapeking before testing any electrical component in the Charging System it is "IMPERATIVE" that you have a fully charged battery of 12.5 volts or more and be able to pass a proper "LOAD" test if necessary, you may have a preliminary reading of 12.5 volts or more but little or zero amperage, the battery is faulty and must be replaced. AGM type batteries fall into this scenario more so than lead-acid batteries.
1. Battery Test:
The battery needs to be a fully charged and load tested to ensure proper readings, connections need to be clean and tight. If you are not working with a fully charged and functional battery, all other voltage tests will be incorrect. Standing battery Voltage should be 12.5-13.2 DCV.
2. Charging System Voltage Test:
Start motorcycle, measure DC volts across the battery terminals you should have a reading of approximately 13.2-15 DC Volts.
3. Connections and wires:
Inspect the regulator stator plug, and check the battery terminals for connection corrosion. If everything seems to be in order, move on to number 4 below to determine if there's a failed component.
4. Stator Checks/Rotor Check: Each of the following tests isolates the Stator & Rotor. If AC output and resistance test fail and stator test passes then the rotor is at fault (Pull Primary covers and inspect rotor for damage).
5. AC Output Check:
Unplug the regulator plug from the stator start motorcycle and change Voltmeter to AC volts. Probe both stator wires with your meter lead. The motorcycle should be putting out approximately 18-20 ACV per 1,000 rpm. Reading will vary depending on system, check service manual specification
Generic Specs:
22 amp system produces about 19-26 VAC per 1,000 rpm
32 amp system produces about 16-20 VAC per 1,000 rpm
45 amp system produces about 19-26 VAC per 1,000 rpm
Stator Resistance Check:
Switch your multimeter to Ohm x 1 scale. Probe each stator wires with meter leads and check resistance on the meter.
Resistance should be in the range of 0.1-0.5 Ohms. Reading will vary depending on the system, check the service manual for specifications.
Generic Specs:
22 amp system produces about 0.2 to 0.4 ohms
32 amp system produces about 0.1 to 0.2 ohms
45 amp system produces about 0.1 to 0.2 ohms
5. Stator Ground Check:
Switch your multimeter to Ohm x 1 scale.
Probe each stator wire with your positive lead on the multimeter and the negative to ground.
There should be no continuity to ground on either wire.
If there is continuity your stator is shorted to ground and must be replaced.
6. Regulator Test:
Each of the following tests isolates the regulator only, so if any of these tests fail, the regulator is at fault.
Identifying Wires:
Battery Charge Lead- Wire going from the regulator to battery positive.
AC output leads- Wires coming from the Stator to the regulator.
Ground- Wire from Regulator to ground or regulator may be grounded via the physical bolting to chassis.
Regulator Ground Test: Ensure the regulator body is grounded or grounding wire is fastened tightly to a good ground (you should verify this by checking continuity from the regulator body to chassis ground).
Fwd/Reverse Bias Test/Diode Test:
This check is testing the Diode function to ensure it is regulating the AC current for the stator into DC Current.
Switch multimeter to Diode Scale.
Place your Multimeter positive lead on each AC output wire.
Place your multimeter negative lead on the battery Charge wire.
The meter should read voltage typically around .5 volts.
Next, switch your multimeter leads putting the negative lead on the AC output wires and the Positive lead on the Battery Charge Wire. The reading should be Infinite. With your meter on the same setting, place your multimeter positive lead on the regulator ground wire or to the regulator directly, and then place your meter negative lead on the AC output leads.
The meter should read voltage typically around .5 volts.
Next, switch your multimeter leads putting the negative lead on the regulator ground and the Positive lead on the AC output wires. The reading should be Infinite.
Note: Below is a table to show the readings:
Positive Lead Negative Lead Reading
AC output 1 Battery charge lead Voltage
AC output 2 Battery Charge Lead Voltage
Battery charge lead AC output 1 ?
Battery charge lead AC output 2 ?
Ground AC output 1 Voltage
Ground AC output 2 Voltage
AC output 1 Ground ?
AC output 2 Ground ?
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You can find a diagnosis guide that I personally authored at this site:

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