Electronic Ignition Systems for Lambretta: Systematic Troubleshooting by Ignition Type

No spark, misfires, or a weak spark? Most problems can be easily found with a multimeter and some systematic approach—without getting fu***d up straight away.

Basic procedure (applies to all systems):

1. Visual inspection of wires, connectors, ground connections, high-tension cables, spark plug
2. Replace the CDI with a known-good unit. The fastest and most reliable test for CDI problems. 
3. Test the stator with a multimeter

Ducati 6-pin systems (BGM, Indian/SIL, AF Rayspeed, Vespa PX-based, etc.)

By far the most common system. Pay attention to the wire colors. Here’s an explanation for BGM- and Vespa-based Ducati ignition systems:

• White = Earth
• Red = Pickup / Trigger
• Green = Low-tension / Field coil
• Yellow = Lighting

Resistance measurements (set multimeter to Ω, cables disconnected from the CDI):

 

Common Issues & Tips:

• Pickup height: If the trigger at the flywheel / rotor are not aligned with the pickup of the stator plate there will occure problems. If the pickup is too low, there is no spark; if it is too high, there will be misfire at higher revs.  This is common with AFR flywheels. As a general rule, for LI/SX cones: the pickup must be raised by about 1 mm. For DL/GP cones: the pickup must be lowered by about 1 mm. The bgm flywheel and stator plates are a perfect match out of the box. 
• Mixed components (e.g., AFR flywheel + no-name CDI) → often cause misfires at high RPMs.
• Check the lightning output: The white ↔ yellow cables should have very low resistance (approx. 0.4–1.8 Ω depending on the stator). The easiest way is to set the multimeter to AC voltage (V~ / AC) while the engine is running and measure the input and output voltages at the voltage regulator and from the stator plate. The input voltage should be between 15 and 36 V depending on revs. The voltage that comes out of the regulator should be around 13.8 V. 

Repair: The pickup and LT coil can be replaced individually. The bgm Orange pickup features an optimized and more durable design. 

Original Innocenti GP 200 Electronic (Ducati 6-pin, very rare)

Same design as above, but with different wire colors and one important electrical feature.

Original color code:

• Green = to ignition switch / kill
• Red = Pickup
• White = Low tension / field coil 

Special feature: The pickup wire does not go directly to ground, but is internally connected to the LT coil.

Resistance measurement:

• White ↔ Red: 550 ± 50 Ω (significantly higher than in later systems!)

The original red Ducati “901” CDIs (525301) are extremely rare and expensive. Modern Vespa PX CDIs will work if you swap the green and white wires. In that case, it makes sense to match the wires of the stator plate to the CDI’s colour coding using coloured heat-shrink tubing. Alternatively, you can adjust the color scheme on the CDI itself.

Otherwise, the same mechanical tips apply as for modern 6-pin systems (grounding, pickup height, vibrations).

 

Spare parts:

BGM8037

1231096

BGM8000S05

BGM6669

   

IDM-based ignition systems (Varitronic, Parmakit, Gori Pulsar, Scootopia, very old Casatronic)

4-pole systems with a preset adjustment curve of the ignition timing. Typically: relatively dim light at low RPMs.

Resistor values (typical):

Measurement	Specified value
Blue (earth) ↔ Black/Red	300 ± 15 Ω
Blue ↔ White/Red	0.80 ± 0.1 Ω
Blue ↔ White/Yellow	0.64 ± 0.1 Ω
White/Yellow ↔ White/Red	0.16 ± 0.1 Ω

Important Notes:

• Light output is rather weak at idle → bgm LED taillights can help.
• The Gori Pulsar and Scootopia are technically very similar (1.8 kg flywheel, similar power curve).

 

Replacement parts:

BGM6697

7676869

3332615

   

Vape Ignition

Czech made univeral ignition that is adapted to the Lambretta. Fins are screwed to the rotor. Different CDI units are available.

Resistance measurements:

Critical points:

• Grounding is everything. The Vape has no ground connection from the stator to the CDI. Therefore, a good ground connection is required between the motor ↔ frame and the frame ↔ CDI steel housing. Without a sufficient ground connection, the CDI may be damaged, resulting in no ignition spark. 

Troubleshooting: If the resistance readings are correct but there’s still no spark → first check the ground connections and the CDI connector. The CDI is sensitive to a lack of ground and can practically only be tested by replacing it.

BGM9404V

BGM9404S