LAMBRETTA ELECTRICS
Li light switch
12 volt conversion
LED Lighting

Possibly the most troublesome area on a Lambretta especially when rebuilding a machine which may have been lying around for some time. Check the obvious things first such as broken wires or insulation and dirty connections and contacts. Clean any verdigris (the green coating which develops on brass and copper) off of the connectors and from those switches which can be taken apart such as the light switch. When disassembling the light switch be aware of things popping out such as the springs, ball and roller (see drawings). Also make sure all earth connections are sound, scrape away any paint where the are attached  to the frame. A cheap multimeter is useful for checking continuity of cables and connections. If it is not known whether the magneto is working properly a simple test is to connect a bulb between each of the cables from the stator plate to earth and kick the engine over. If the bulb does not light then stator needs checking out or possibly the flywheel may need re-energising, if it lights then continue connecting components and testing each one. When removing the flywheel during a rebuild or restoration it is worthwhile having the flywheel checked anyway. 
Li Light Switch:

Drawings of the Li light switch with cut-aways showing the spring loaded ball on the main light switch and the spring loaded roller on the dip switch. 
There are some minor variations to these switches in the way they are assembled, but operation is the same. Also some models used a similar switch when fitted with indicators in which case the wires are of different colours.
  
   off position                                                  parking/pilot light on                                headlight on

 
  dip-beam position                                         full-beam position                                       switchover position        
The switch is designed with a small gap between the brass strips of the dip and main beam contacts so momentarily both the dip and head beams are on in the switchover position. This is to prevent a surge of power to the tail light which can blow the rear bulb. When re-assembling the dip switch the pin is fitted with the swaged end to the front as in the drawing. Re-assembly of this part is rather fiddly but a small screwdriver used to position the roller helps
12 Volt Conversion:

       A conversion to 12 volts was decided upon after suffering problems with bulbs blowing and difficulty in obtaining the correct bulbs (or even finding 6volt bulbs at all). The original stator was replaced with a stator from ScootRS along with a 12 volt regulator (Vespa PX non-battery) and HT coil. This came fitted with 12volt coils and standard points having 2 wires out (power and ignition). Alternatively coils are available which are used to replace the original coils and rewired as instructions on the ScootRS website or there is a section on the LCGB website showing how to rewire original stator for 12 volts. 
       The modified wiring diagram below is for the Series 3 Li non-battery model, other models being wired to the regulator in a similar way. For a battery model  use a PX battery model regulator. The regulator will need mounting somewhere, the most convenient point being on a bracket on the opposite side to the coil on the rear frame or to the rear strut.  The original horn will still work but all bulbs will need to be replaced with 12 volt ones. In this case a halogen bulb was fitted in the headlight and an LED stop and tail bulb. Although in this case the LED bulb is in use on an AC system and should therefore only light on half the cycle this is not evident nor does there appear to be any loss of brightness.


The coil has the same fixing hole centres as the original holes  in the frame so fits without any modifications to either.

The regulator fitted on the opposite side to the coil using a simple bracket.
On the left is a drawing for the bracket used to mount the regulator as above. Check the hole centres on the frame and the regulator and modify if necessary or mark the holes from the coil and regulator. Similar brackets are available from some dealers 

LI Series 3 non battery 12V wiring diagram
LED Lighting:

    One problem encountered with non-battery Lambretta's is that of the headlight dimming when the brake is applied. A way round this is to fit an LED bulb in place of the standard stop/tail rear bulb. Also when additional lights are fitted (whether on a a battery or non-battery model) these can cause a drain on the system. LEDs (light emitting diodes) work in the same way as ordinary diodes, in as much as they only allow current to flow in one direction but lighting up when the current flows through them. These will work fine with a DC (direct current) supply but with an AC (alternating current) they will only light half of the time (see diagrams).
    

               

          Typical AC sine wave, an LED will only light  when the voltage is above 0 as shown above right.

    A solution to this is to use a rectified supply. that is a supply that is converted to DC. The simplest way of  achieving this is to use a bridge rectifier, either custom made using suitable diodes or ready made bridge rectifiers can be purchased quite cheaply.

                                    
Rectifying:

                         

          Showing how a bridge rectifier changes AC supply, left, to DC and below the resultant waveform.

                       

 
Smoothing;

    Even using a bridge rectifier the voltage is rather uneven but unlikely to matter too much. If  a more constant voltage is required then a capacitor needs to be added in the DC circuit. The resultant flow is shown below

                        

 
    There are other drawbacks such as LED,s having a threshold voltage at which the will light therefore there is a possibility that they may not light at tick-over, although I have not found that myself only a flickering caused by the irregular output at that speed which is evident with conventional bulbs. LED's also have a low tolerance to reverse current, approximately 5 volts, above which the can burn out, although I have not had a problem with this.
Note: The information above is only from my own limited understanding of electrics and it is recommended that if more detailed information should be required that an online search be made.

Home  |  Scooter Pages  |  DIY Pages  | Galleries