Stator rebuilds Lambretta & Vespa | WORKSHOP
Electrics scare the bejesus out of a good many talented mechanics.
The difference between nuts and bolts and electricity is one of visibility. Most spanner-monkeys can visualise and understand things that are constructed like Meccano, but electricity is black-magic hidden inside coated wires and sealed boxes that never move. Electrical items rarely look any different whether working or broken.
Staffordshire scooterist Anthony Tambs of Scootronics has no such fear. He’s worked with electronics most of his life and has an impressive understanding of what makes spark-plugs tick. Literally.
Scootronics is a relatively new business which is brimming with innovations that we’ll cover here on SLUK in the fullness of time, but include:
- An external pick-up ignition kit that allows your timing to be adjusted without removing the flywheel. It can even be used to convert non-electronic ignition flywheels to electronic ignition.
- Also the new Intelli-converter box which allows scooters with AC (non-battery) ignitions to power accessories like mobile phones and sat-navs. There have been previous boxes that provide these functions, but Anthony’s is far more sophisticated as we’ll explain in the future.
For the moment though, let us concentrate on what Anthony has been making his name with and that is stator plates and their repair.
What stators are we talking about?
For the purposes of this article we are only concerning ourselves with 6-pole stator plates as fitted to:
- Vespa PX series
- Vespa PK series
- Many LML models
- SIL Lambretta electronic
- Lambretta AF Electronic
- BGM stator
- Several other aftermarket stators
Ignitions: what goes wrong?
There are 3 or 4 basic circuits on these stators, but only 2 concern the ignition:
- The Low Tension (LT) coil: the white-taped one with the copper washer retainers. This provides the power for the spark via the Green wire (on Italian systems).
- The pick-up coil: the black one screwed to the stator: this provides the timing pulse to fire the spark via the Red wire (on Italian systems).
Common faults are:
- Internal failures of the stator red/white/green wires (particularly Piaggio ones)
- Internal failures of the pick-up or LT coils on some brands of stator
- Coil failures due to loose earth tags on the stator (particularly Indian ones)
- Poor running due to incorrect pick-up height with respect to the flywheel triggers (particularly mismatched Lambretta flywheel/stator combinations)
Both the Pick-up and LT circuits can cause trouble. The traditional roadside tests are to check the resistance or red/green wires compared to the white (earth) wire using a multimeter.
- Red (pick-up) to White (earth) usually around 100-120 Ohms
- Green (low tension) to White (earth) usually around 400-500 Ohms
However, as Anthony pointed out, these figures are not a reliable way to test pick-ups as these contain two coils, one of which may be broken but the pick-up can still read within limits.
Essentially a multimeter resistance test is only useful to test for wire failures which will read infinity (∞) or a flashing 1 on a digital multi-meter.
VIDEO | Stator rebuild
Many people now tend to buy new aftermarket stator plates to replace failed ones, but often these are no more reliable in the long term.
Anthony’s preferred solution however, is to repair old stators by replacing the LT coils and pick-ups. His hand-repaired stators now have a great reputation in the trade and are available from several UK dealers.
The video above shows quite how much work is involved in repair of a stator.
- Stator laminate thickness: If you want to replace the LT coil you need the correct thickness coil. Most stators have 13mm thick laminates, but some others (like BGM and VE) use 11mm thick laminates
- Replacement part quality: Not all coils are made equal. For pick-ups Anthony has found coils had good results with both LML and K2 coils from India. For LT coils Anthony has also found coils he is happy to use from India.
- Bad Earths: Most of the coils that burn out are due to bad earths rather than poor manufacture so correct fitting is vital.
Hopefully with this video a few of you will gain enough knowledge to do better quality repairs to your own stators.
For those who are still more afraid of wires than snakes, then Anthony is in the process of producing his own Lambretta stator plates from scratch using high quality coil and laminate packs.
For more on this see his Scootronics Facebook page.
Anthony has found that pick-up misalignment due to varying pick-up heights on different types of aftermarket stator plates can affect high rpm running. The taller one pictured is standard SIL and designed to work correctly with the standard SIL flywheel.
The second type shown is a common aftermarket stator which has a pick-up almost 2.5mm lower and is therefore misaligned with the triggers inside and SIL flywheel.
This situation can be simply remedied however by raising the stator on some CNC packing plates that Anthony has had made.