FAQ

Here are answers to some of the most Frequent Asked Questions from our customers.

(We will add more FAQs to this page over time, so please Bookmark this website and revisit.)

I have a JG Unit but don't know what sort it is. How can I tell?

Look at the colours of the 3 wires coming out of the unit: Yellow/Green/Black is 6v positive earth; Orange/Brown/Red is 6v negative earth; Blue/Green/Black is 6/12v positive earth; Orange/Green/Red is 6/12v negative earth.

Why don't you supply "off the shelf" Magnetos and Dynamos?

We specialize in the bespoke restoration of customers' own units for those who want to keep their machines as original as possible, and we are too busy with this to build up a stock of spare units. Also, even with the most common Magnetos and Dynamos, there are several different types so it is difficult to match exactly what is required. We prefer to provide an individualized service.

My Magneto works fine, but the engine is difficult to start when hot.  Why is this?

This is the most common sign that a Magneto needs attention.  Usually, it is caused by the condenser leaking, but it can also be the winding breaking down, or both.

Can I rewind my Magneto armature myself?

Well, there is nothing to stop you having a go, but you are unlikely to succeed!  The coil needs many thousands of turns of wire which is thinner than a human hair, and laying this on properly is a skillful job which requires a specialist winding machine.  The wire must be wound tightly, but can easily break if you don’t know how to handle it.  Also, it needs careful insulating to ensure there is no tracking.   (I have heard of somebody who wound their own coil by rotating the core on the end of an electric drill and feeding the wire on by hand – but this may just be one of those stories that goes round!)

Should I switch to Electronic Ignition?

A Magneto which is in good condition and properly set up is a very reliable unit, and can give decades of trouble-free motoring, without any major repairs.  “If it’s not broke, why fix it?”  It’s true that a badly-repaired Magneto is no use to anybody, but it’s also true that some electronic ignition systems are not of a high standard.  Also, bear in mind that electronic ignition relies on the charging system of the bike or car, but a Magneto doesn’t.  Also, a Magneto usually gives fair warning that it is on the way out, whereas an electronic ignition system can fail quite suddenly.

Do you sell switches, ammeters and lamps?

No, mainly because the quality of pattern items is inconsistent.  We have chosen to specialize in Magneto and Dynamo spares.

What is so good about the JG Electronic Regulator?

The JG Unit is a sealed solid-state electrical component.  It has no moving parts.  This removes the necessity to set points or air-gaps.  Also, it is immune to the problems of moisture, vibration and heat, which are the traditional enemies of the Regulator. JG Units come in 6v, 12v or 6/12v conversions.

How does the JG 6v to 12v conversion Electronic Regulator work?

Using a normal 12v Regulator would work on a 6v Dynamo, but it would subject the Dynamo to excessive heat (it would actually produce 4 times the heat through the 6v field coil).  The 6/12v JG Unit has extra circuitry which protects the field coil from overheating.  This allows the 6v Dynamo to work on 12v without the fear of it burning out.

Should I convert my Dynamo from 6v to 12v ?

A 12v system has the advantage of allowing better lighting, and our 6v to 12v JG Electronic Regulator allows you to convert your Dynamo to 12v.  If your machine is not used much at night, then staying with 6v may be okay.  One disadvantage of 12v is that it requires a non-standard-looking battery (if your battery is on display). We do not recommend putting a small 12v battery in a hollowed-out 6v battery case, as the Ampere Hour rating on such a small battery could be too low.