Forum

[Norm]

It is interesting to note that the CB Honda boys have started fitting a relay to poer the coils on their bikes. This was brought about by somebody discovering that the voltage drop to the coil eas significant through the wiring loom 12.5 volts at the battery, ignition on voltage drops to 12.1 volts but voltage at the coil is 10.1. Not sure if this would help a Bullet but you never know

[Frank]

That quite some voltage drop. I've never heard of it on a bike, but perhaps the coils run via a ballast resistor and so the lower voltage is correct.

[Norm]

Hi Frank,
In cars I have seen resistor wiring used, the start wire bypasses the resistor wire, start with 12volt, release the key and it drops back to 9 volts for run but I haven't heard of it in a bike. These boys also make reproduction wiring looms so I think they would have worked out if there was a resistor in the loom somewhere. Probably doesn't matter too much with a Bullet but I might set one up this way to see if it helps

[Alan R]

Hi guys-----------NORM, my 1975 Honda GL1000 Goldwing has (Had) a ballast resistor in the starting wiring loom and the key operates it just as you describe............... I've removed it, joined the resulting wire-ends together etc. because the pattern HT coils supplied today are a straight 12 volt and would otherwise burn the points out, el pronto !! ( ps---- starts and runs perfectly a-ok so is one item less to go wrong on a very complex bit of kit !!)-----------

[Frank]

Norm, as you say it is an aid to starting to give the coil an extra kick when the starter is draining the power. Like you i'd never heard of one on a bike but as Alan says they obviously were. If the CB'ers haven't got them then I would have thought it would be better to investigate the cause of the drop than work around it with a relay. Just adds another fault liability. Treat the cause not the symptom!

[Norm]

Hi Frank, far be it from me to tell those CBérs how to suck eggs the knowedge base there is just amazing. They have members scattered around the world making various components that are NLA from Honda just to keep them going, a bloke in NZ makes cam chain tensioners, another makes clutch rubbers another makes a special clutch pus pad,another makes reproduction wiring looms, the list goes on so I won't stick my head in and tell them how they should fix the wiring lol

[Norm]

I ended up asking the question, and the thoughts are that with 30+ year old wiring harness and tired connectors and switches this is where the voltage loss occurs so fitting a relay and dumping 12 volts directly to the coils is the best fix, or fit a new harness

[rep_movsd]

A mechanical relay for a 7500 RPM engine?
That is a little crazy!

Relays are not reliable for such rapid switching - sure your points will live longer because they are not carrying the coil current, but the relay contacts will and they will burn due to arcing caused by the rapid make-break.

A solid state relay will work, they are rated for hundreds of kilohertz.

[Alan (Lancashire)]

me thinks norman meant that they were using a relay to assist the battery voltage to the coil , not the switched points side

[Norm]

Hi Alan you are correct, and it is interesting watching the CB forum, one of the first things that is asked if anybody is having ignition/coil problems they are asked if the have done the relay mod. It seems to help solve a lot of problems