Know your Alternator
All Tiger Cub and Terrier models used a 6-volt electrical system from either Lucas or Wipac. The rotor being mounted on the left hand side of the crankshaft running in a stator located inside and fastened to the primary chaincase.
Irrespective of manufacturer, both makes of alternator are physically and electrically interchangeable. The Wipac stator is of very similar dimensions to the Lucas 74mm item*, although it has slightly different coloured wires to the Lucas ones.
If replaced with a Lucas stator there may well be a slight increase in the air gap between stator and Wipac rotor, but this should not noticeably affect output.
* The early Lucas RM12-15 series alternators used a small 70mm diameter rotor. Later RM-18 to 19 units used a larger 74 mm rotor and were fully encapsulated to protect the windings and help prevent the coils coming loose.
The RM19 being the most powerful 6-volt unit and much thicker then previous versions. Having said that, all the round frame RM alternators use the same mounting pattern and are interchangeable.
If replaced with a Lucas stator there may well be a slight increase in the air gap between stator and Wipac rotor, but this should not noticeably affect output.
* The early Lucas RM12-15 series alternators used a small 70mm diameter rotor. Later RM-18 to 19 units used a larger 74 mm rotor and were fully encapsulated to protect the windings and help prevent the coils coming loose.
The RM19 being the most powerful 6-volt unit and much thicker then previous versions. Having said that, all the round frame RM alternators use the same mounting pattern and are interchangeable.
On a number of competition models an Energy Transfer system was used, which enabled the machine to be run without a battery. These models utilised a specially wound alternator stator and coil, and a short open-period contact breaker.
The wiring colours for this system are Brown/Blue, Black/White and Red.
Running clearance
There must be a minimum 0.2 mm (0.008”) clearance between the rotor and stator all the way round. Difficult to check on a Tiger Cub or Terrier due to the separate positioning of items, but if a problem is suspected, remove the primary chaincase and check the rotor and stator faces for signs of rubbing or contact.
If signs are evident and whilst the primary chaincase is removed, clearance can usually be achieved by slightly loosening the stator mounting bolts and carefully tapping the metal surround of the stator nearest to the point of contact with a soft faced hammer before retightening.
The wiring colours for this system are Brown/Blue, Black/White and Red.
Running clearance
There must be a minimum 0.2 mm (0.008”) clearance between the rotor and stator all the way round. Difficult to check on a Tiger Cub or Terrier due to the separate positioning of items, but if a problem is suspected, remove the primary chaincase and check the rotor and stator faces for signs of rubbing or contact.
If signs are evident and whilst the primary chaincase is removed, clearance can usually be achieved by slightly loosening the stator mounting bolts and carefully tapping the metal surround of the stator nearest to the point of contact with a soft faced hammer before retightening.