As part of a 90% restoration, I installed a brand new Lucas stator (RM13, 4 wire) and rotor (RM13 70mm) and aftermarket coil. The rotor had VERY strong magnets. I was kicking 5+volts at the coil from the alternator and was getting what appeared to be a good spark. It still would not start. I took it to a local vintage bike repair shop that confirmed correct distributor and valve timing. They finally found I was only getting an intermittent spark. Any suggestions??
Forget the charging side of things and get a solid reliable spark 1st.
Check points contact quality , condenser and you've bought a new coil.
Just hot wire these 3 components together and it will run assuming you get the spark.
Once running reliably , sort out charging
Hi
Is the 'S' (as in C15S) for scrambles? And does it run an energy transfer ignition or is there a battery fitted?
I see you say the stator has four wires.
The energy transfer ignition always was a bit tricky to start or so I understand.
Someone more expert will no doubt have the answer but I seem to remember reading about needing to time the engine differently and also doing away with the hockey stick kickstart lever as it does not give a very full swing (if indeed that is the type of lever you have).
Start with checking all the electric components are correct for whatever ignition system you are using, I.e. energy transfer or standard DC system. Both those systems use components specific to each.
Which one is it?
Mine has the Energy Transfer System so I can't separate the charging side from the ignition side, they are one in the same. The wire from the stator to the coil puts out 5-6 volts from a swift kick on the starter. I guess I could effectively bypass the rotor and stator by connecting a 6 volt battery directly to the coil input.
The energy transfer stator needs a points cam and ignition coil which are specific for the energy transfer system. If you havnt got them it would be easier to replace the stator for a standard two (or three) wire stator, rectify the output to 12v DC and use the standard coil and points cam.
Therefore which points cam and ign coil have you got? Pictures?
Not sure which points/condenser I have. I do have a new set that I have yet to install. The distributor has never been out of the motor, which the previous owner said was running when he put it away 25 years. I have had no reason to suspect the distributor is incorrectly installed, or very far out of position. The cam appears to be opening the points at the correct time.
Points.jpg
Quote from: Rupert on 01 Sep, 2025, 19:33 The energy transfer stator needs a points cam and ignition coil which are specific for the energy transfer system. If you havnt got them it would be easier to replace the stator for a standard two (or three) wire stator, rectify the output to 12v DC and use the standard coil and points cam.
Therefore which points cam and ign coil have you got? Pictures?
I take it that the rotor magnets to stator coils are timed to match the points opening so that the peak voltage charges the coil just ahead of the points? Is there scope for putting a big capacitor in to give some flexibility?
Yep, that's the basic principle of the energy transfer system, the points open during the period of maximum magnetic flux/electrical output of the Alternator.
Not possible to store any of that output with a capacitor as the output is AC. But that's overcome in the standard electrical system by rectifying the AC output to DC, then it can be stored in a capacitor or battery.
The pic shows that you have a standard points cam. Two things make it unsuitable for the Enehgy transfer system -
- the shape of the cam needs to have a sharp peak with no dwell with the points open.
- the advance range is typically only 5° to make sure the points open during the period of maximum magnetic Flux.
At least there are obvious reasons why your ignition system doesn't work!
Thanks for explaining. Schoolboy error by me forgetting the capacitor will need DC.