Lucas Rita no spark

L.A.B. said:

The AB5 has a finned case.

Grant Tiller | Norton Commando Wiring Diagram + Lucas RITA AB5

This is a follow up to my other post covering the more common Lucas RITA AB11, which you can find here. As I mentioned, there is an earlier electronic igniton called the Lucas RITA AB5. They are not very common at all, and the wiring color scheme is different to the more popular AB11. The

granttiller.com

To avoid confusion the rotor is the "Reluctor":

Click to expand...

Lostcause said:

Hi,
I am working on a MK3 commando which has a Lucas Rita ignition fitted (AB5 I think). It has been stood a number of years but was supposedly running fine when parked up.
When I turn over the engine there is no spark.

It has: new battery & new spark plugs,

The reluctor has a resistance of 270 ohms & a gap of 0.2mm to the rotor tips, there is 12v to the ignition amplifier unit, the coils measure 1.5 & 2 ohms on the primaries and 5k & 6.5k ohms on the secondaries. Both HT leads are good & the caps each measure 5k ohms.

There is a spark when I turn off the handlebar run switch & if the reluctor is bridged to the rotor with a screw driver yet nothing if the screwdriver is just passed near the tip of the reluctor or the engine is turned over!

Does anyone have any suggestions?


I am unfamiliar with Lucas Rita systems, my own 850 / wideline special has a Boyer.

Cheers- Steve

Click to expand...

Lostcause said:

There is a spark when I turn off the handlebar run switch...

Click to expand...

Lostcause said:

...the coils measure 1.5 & 2 ohms on the primaries

Click to expand...

Lostcause said:

Hi,
I am working on a MK3 commando which has a Lucas Rita ignition fitted (AB5 I think). It has been stood a number of years but was supposedly running fine when parked up.
When I turn over the engine there is no spark.

It has: new battery & new spark plugs,

The reluctor has a resistance of 270 ohms & a gap of 0.2mm to the rotor tips, there is 12v to the ignition amplifier unit, the coils measure 1.5 & 2 ohms on the primaries and 5k & 6.5k ohms on the secondaries. Both HT leads are good & the caps each measure 5k ohms.

There is a spark when I turn off the handlebar run switch & if the reluctor is bridged to the rotor with a screw driver yet nothing if the screwdriver is just passed near the tip of the reluctor or the engine is turned over!

Does anyone have any suggestions?


I am unfamiliar with Lucas Rita systems, my own 850 / wideline special has a Boyer.

Cheers- Steve

Click to expand...

Lostcause said:

Hi,
I am working on a MK3 commando which has a Lucas Rita ignition fitted (AB5 I think). It has been stood a number of years but was supposedly running fine when parked up.
When I turn over the engine there is no spark.

It has: new battery & new spark plugs,

The reluctor has a resistance of 270 ohms & a gap of 0.2mm to the rotor tips, there is 12v to the ignition amplifier unit, the coils measure 1.5 & 2 ohms on the primaries and 5k & 6.5k ohms on the secondaries. Both HT leads are good & the caps each measure 5k ohms.

There is a spark when I turn off the handlebar run switch & if the reluctor is bridged to the rotor with a screw driver yet nothing if the screwdriver is just passed near the tip of the reluctor or the engine is turned over!

Does anyone have any suggestions?


I am unfamiliar with Lucas Rita systems, my own 850 / wideline special has a Boyer.

Cheers- Steve

Click to expand...