- Joined
- Aug 18, 2008
- Messages
- 198

A year or so ago, I said to a friend of mine, who happens to be a longstanding Yamaha dealer, that my old Norton had an electrical problem. He replied that a Norton WAS an electrical problem. I think that he is correct.
My 1970 Roadster has had a longstanding problem of losing charge, and being totally incapable of running for any time with the headlight on. Almost all of the time that I have been riding it – the last few years, the ammeter on the headlight (it is one of the earlier models that still has this) has had the needle firmly in negative territory; only when I am at highway speeds at about 4000 revs would it waver into positive. As the bike runs Boyer ignition this pretty soon translated into missing and stalling.
In order to resolve that issue I have recently installed a Sparx three phase alternator, and Sparx regulator rectifier. That was not without issue – the system initially did not put out the voltage that it should have. It transpires that the new spark plug leads that I bought and thought were not resisted leads – they are connected to 5000 ohm resister caps as recommended – were resisted leads – I have not tested them but the manufacturer’s helpline advised that they were resisted to about 900 ohms. With those leads on the regulator would only put out a maximum of 12.5 volts, and the ammeter still ranged between about -12 and -4 during most rev ranges. I have now changed the leads to copper leads – with the 5000 ohm caps, and that appears to have cured the problem; the regulator is now putting out 14.1 volts and 3 amps at idle, and 14.69 volts and 12.3 amps at between 3000 and 4000 rpm with the headlight on. The alternator is putting out about 15.5 volts from each of its three phases at idle, raising to over 30 volts at revs. So I am happy with my Sparx system.
However, the ammeter on the headlight still points to negative for most of the time, except when I am on the highway at 4000 rpm; when it fluctuates wildly but appears to hit positive. With the headlight on at say 2000 rpm it will show -12 amps. Is that normal? Or is it an indicator of a problem somewhere in the circuit that is taking all of the power that is being generated by the alternator and regulator? Or is it just what is to be expected to be used through the ignition system – and brake light; and headlight when it is on?
Could it be that the ammeter is defective, and if so, how can I test it? If I did not have the ammeter, as later models don’t, I would not be aware of any potential issue. I am not aware of any issues with the running of the bike – but since curing the spark plug leads issue I haven’t had the opportunity to go for a long run to see if any issues arise if I have the headlight on for a few hours. I am running a new 7ah battery.
My 1970 Roadster has had a longstanding problem of losing charge, and being totally incapable of running for any time with the headlight on. Almost all of the time that I have been riding it – the last few years, the ammeter on the headlight (it is one of the earlier models that still has this) has had the needle firmly in negative territory; only when I am at highway speeds at about 4000 revs would it waver into positive. As the bike runs Boyer ignition this pretty soon translated into missing and stalling.
In order to resolve that issue I have recently installed a Sparx three phase alternator, and Sparx regulator rectifier. That was not without issue – the system initially did not put out the voltage that it should have. It transpires that the new spark plug leads that I bought and thought were not resisted leads – they are connected to 5000 ohm resister caps as recommended – were resisted leads – I have not tested them but the manufacturer’s helpline advised that they were resisted to about 900 ohms. With those leads on the regulator would only put out a maximum of 12.5 volts, and the ammeter still ranged between about -12 and -4 during most rev ranges. I have now changed the leads to copper leads – with the 5000 ohm caps, and that appears to have cured the problem; the regulator is now putting out 14.1 volts and 3 amps at idle, and 14.69 volts and 12.3 amps at between 3000 and 4000 rpm with the headlight on. The alternator is putting out about 15.5 volts from each of its three phases at idle, raising to over 30 volts at revs. So I am happy with my Sparx system.
However, the ammeter on the headlight still points to negative for most of the time, except when I am on the highway at 4000 rpm; when it fluctuates wildly but appears to hit positive. With the headlight on at say 2000 rpm it will show -12 amps. Is that normal? Or is it an indicator of a problem somewhere in the circuit that is taking all of the power that is being generated by the alternator and regulator? Or is it just what is to be expected to be used through the ignition system – and brake light; and headlight when it is on?
Could it be that the ammeter is defective, and if so, how can I test it? If I did not have the ammeter, as later models don’t, I would not be aware of any potential issue. I am not aware of any issues with the running of the bike – but since curing the spark plug leads issue I haven’t had the opportunity to go for a long run to see if any issues arise if I have the headlight on for a few hours. I am running a new 7ah battery.