twin output coil (2014)

I'm thinking about getting a twin output coil - reasons being to firstly to promote simplicity and reliability - I have had one breakdown when the wire between the two coils vibrated off (my own poor handiwork) and a suspicion that it cannot be good to have the connection between the two coils uninsulated and open to the elements, and secondly minimise the clutter of the twin coils that are so close to the top of the cylinder head; I am always concerned that there is not a lot of room with the motor vibrating, so that the leads from the coils to the spark plugs have to be twisted quite severely to get them out of the way; which could lead to them becoming loose or failing.

RGM put out their own twin coil that seems a lot less expensive than some alternatives. Has anyone had experience of the RGM twin output coil? Any issues? The fact that it is relatively inexpensive is on the one hand attractive; on the other hand has me questioning whether quality is inferior to others. I suspect that it is more likely that the price has been set as a geniune reflection of the cost of production; and that some other prices are calculated to be about the same as two 6 volt coils or slightly more than that.

And now for the question that reveals my ignorance. I have boyer ignition, and two six volt coils currently - wired together. Should I be getting a 12 volt output twin coil or a six volt output twin coil?

Chris T said:

I have boyer ignition, and two six volt coils currently - wired together. Should I be getting a 12 volt output twin coil or a six volt output twin coil?

Click to expand...

12V.
Make sure any dual coil you buy falls within the: "more than 3 Ohms" primary resistance rating as specified by Boyer.
http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf

"to have the connection between the two coils uninsulated "
? Not sure what you mean...

6V dual output.

I've been using Harley Dual fire coils that are 12volt,but are 3 ohms with all of my electronic ignitions with great success for many years.

twin output coils of Jap bikes work well. Cheap at the bike wrecker

concours said:

6V dual output.

Click to expand...

As it's a single coil instead of two connected in series, it needs to be '12V''.
A 6V dual coil would not generally have the correct primary resistance:
http://www.boyerbransden.com/coils_ball ... _plug.html

COIL00004 12 VOLT DUAL OUTPUT 4.5 OHM PRIMARY
COIL00012 6 VOLT DUAL OUTPUT 2.2 OHM PRIMARY

Click to expand...

concours - what I am meaning is that my twin coils have copper spade connectors on each side of the front of them; to which wires wires connecting the coils to each other; the transister box, and earth are attached - I don't have a photo, but the diagram that LAB has posted shows them. On my coils the spade connector is in each case "U" shaped (and in turn is connected to the coil with a screw/stud and nut), with one unused side of the "U"connector on each side of each coil. The wires are all insulated, but the spade connectors are bare, and I have always surmised that there must be a risk of something touching them and shorting; especially if they get wet.

Chris T said:

On my coils the spade connector is in each case "U" shaped (and in turn is connected to the coil with a screw/stud and nut), with one unused side of the "U"connector on each side of each coil.

Click to expand...

You could remove the spade connectors and use ring terminals?

Chris T said:

RGM put out their own twin coil that seems a lot less expensive than some alternatives. Has anyone had experience of the RGM twin output coil? Any issues? The fact that it is relatively inexpensive is on the one hand attractive; on the other hand has me questioning whether quality is inferior to others. I suspect that it is more likely that the price has been set as a geniune reflection of the cost of production; and that some other prices are calculated to be about the same as two 6 volt coils or slightly more than that.

And now for the question that reveals my ignorance. I have boyer ignition, and two six volt coils currently - wired together. Should I be getting a 12 volt output twin coil or a six volt output twin coil?

Click to expand...

Chris, I have purchased an RGM coil and on inspections the quality seems to be what you should expect, no problem. I did contact RGM and was told: 'I have used and supplied lots of these'. Certainly I felt RGM are confident they are a good choice.

I have yet to actually use it.

For ignition I am installing a Boyer, set up for crank triggered ignition. The difference is in the pick up not the 'box'.

The ignition was supplied by Steve Maney and is what he has used on race bikes for some time. In his supplied instructions he recommends a dual output 3ohm 12V coil (the sketch even looks a bit like the RGM one. As you say the main choices for these are the 'Dyna' Harley style coils selling in the UK around £70 and the RGM at around half that. I am sure that functionally they are very similar. My choice was influenced by price, the mounting options, the size and the HT lead exit direction. The coil will be mounted under the central frame rail (Rickman not Commando so the motor is vertical and there is no head steady in the vicinity). The coil will sit in line with the bike centreline with the HT leads exiting to the rear and I will cut the leads down ro remove excess.

If you have 6 volt coils you should have a ballast resistor fitted, that as far as I can see is not needed with the 12V coil (there isn't one in Steve Maney's diagram.

RGM also had this to say:

'Of course if you have a Boyer one duff coil could drag down the other but you would be suprised how many times I have talked to people with the Commando complaining about poor starting and it turns out they have fitted a pair of 12V coils and the poor Boyer is having to fire a 24volt coil'

Good argument for the single, dual output coil, and for not using two 12V coils!

Chris T said:

concours - what I am meaning is that my twin coils have copper spade connectors on each side of the front of them; to which wires wires connecting the coils to each other; the transister box, and earth are attached - I don't have a photo, but the diagram that LAB has posted shows them. On my coils the spade connector is in each case "U" shaped (and in turn is connected to the coil with a screw/stud and nut), with one unused side of the "U"connector on each side of each coil. The wires are all insulated, but the spade connectors are bare, and I have always surmised that there must be a risk of something touching them and shorting; especially if they get wet.

Click to expand...

Ok, the double spade lugs were very close to the rocker cover nuts, upon suggestion from a master, I ditched them, used uninsulated #10-16 rings with a bit of shrink tube. Gave more clearance. As for rain, it's low voltage, so no trouble.

L.A.B. said:

concours said:

6V dual output.

Click to expand...

As it's a single coil instead of two connected in series, it needs to be '12V''.
A 6V dual coil would not generally have the correct primary resistance:
http://www.boyerbransden.com/coils_ball ... _plug.html

COIL00004 12 VOLT DUAL OUTPUT 4.5 OHM PRIMARY
COIL00012 6 VOLT DUAL OUTPUT 2.2 OHM PRIMARY

Click to expand...

Click to expand...

Don't want to challenge you, but, at least one other person had the same thought process as I did. Help me understand..,

http://www.commandospecialties.com/Prod ... ProdID=188

concours said:

L.A.B. said:

concours said:

6V dual output.

Click to expand...

Don't want to challenge you, but, my thinking is only one coil fired at a time... at least one other person had the same thought process as I did. Help me understand..,

http://www.commandospecialties.com/Prod ... ProdID=188

Click to expand...

Click to expand...

In the oem points ignition, each set of points/oem coil fires its plug individually so they are, in effect, two separate systems. If you go to an electronic ignition, as far as I know, they all use a wasted spark system and fire both coils/plugs at the same time. I installed a pair of new "oem" type coils from Old Britts in '06, using them on my oem ignition (I had removed the Boyer/single coil that was on the bike when I bought it and installed the oem ignition). Then, when I went to the Trispark in '08 or thereabouts, I just kept those coils which now operate as wasted spark with the TS ignition.

Concours, it is simple really....

Points ignition fires each cylinder only on compression stroke, there is a set of points fo reach cylinder but the AAU only opens one set at a time, so each set of points triggers its coil at 360 degree intervals, or 720 cranshaft degree intervals....the 2 coils are wired one each to each set of points...so each cylinder runs independently and only sparks on teh compression stroke.

If the coils are 6V with point ignition they need to be wired with a ballast resistor to make sure they are not fed with 12V during normal running ,or they will eventually fail due to the 'overvoltage'.

Why fit a ballast resistor?, well that is to allow a higher voltage to be applied to the coil during starting (short term over voltage achieved by bypassing teh hballast resistor does not harm them). With an electronic ignition an improved spark is available on start up and during normal running, without running a temporary overvoltage to the coil.

As has been suggested all electronic ignitions for Norton 360 degree twins operate a 'wasted spark', meaning that both ignition coils trigger together.

If you install an electronic ignition and you have two 6V coils fitted you wire them in series to provide a suitable load to your 12V supply...and you remove the ballast resistor. You then trigger both coils together...in fact they work as a single 'dual output' unit, in an identical way to a single, dual output 12V coil.

If you have 12V coils fitted you will need to change them to 6V or a dual output 12V if you fit an electronic ignition.

Boyer confuses the issue by having 2 trigger coils, but they both fire together at 360 degree crankshaft intervals (180 degree camshaft intervals). Other cam trigger ignitions only have one trigger coil fired each 180 degree of camshaft rotation, or a single optical trigger.

Crank triggered ignitions use a single trigger, fired once per 360 degrees of crankshaft rotation, it still 'wasted spark'.

concours said:

Don't want to challenge you

Click to expand...

Although Boyer does not specifically state a "12V" dual coil on that particular instruction sheet they do on others:

http://www.boyerbransden.com/pdf/KIT000 ... 00023_.pdf

"......two 6 volt coils in series or one 12 volt double ended coil with a primary resistance of 3 to 4.5
ohms will give the best results.

Click to expand...

concours said:

but, my thinking is only one coil fired at a time...

Click to expand...

As others have said, original points, yes, Boyer (and most other EI) no.

I fitted an Emgo IC05 dual output 12v coil to mine. It's the one recommended by Pazon for use with their electronic ignition systems. You can ditch the ballast resistor. You will need to fashion a bracket / heat sink to keep it in the air stream -- the instructions are very specific about avoiding overheating. I used a piece of plain 3mm aluminium, with some longer bolts and spacers. It works perfectly.

Chris T said:

RGM put out their own twin coil that seems a lot less expensive than some alternatives. Has anyone had experience of the RGM twin output coil? Any issues? The fact that it is relatively inexpensive is on the one hand attractive; on the other hand has me questioning whether quality is inferior to others. I suspect that it is more likely that the price has been set as a geniune reflection of the cost of production; and that some other prices are calculated to be about the same as two 6 volt coils or slightly more than that.

And now for the question that reveals my ignorance. I have boyer ignition, and two six volt coils currently - wired together. Should I be getting a 12 volt output twin coil or a six volt output twin coil?

Click to expand...

I have been using the RGM dual output coil connected to a Pazon Altair EI for a few months now. Starting is as good as it was with the old twin coil setup, idling is reliable, and I've no issues with misfiring or other ignition probs.

Peter

Chris,
I don't know if you can get these over there but the Dynatec DC7-1 is a super solid 5ohm coil that works with all of these EI ignitions. Before the mag, I ran this for years with the Surefire. It is a Sherman Tank of a coil. I am sure the RGM is fine, but I know that this DC7 is awesome.


If you want to keep your original coil bracket with the reflectors you can do it like this. This way requires a little trimming of the bracket.


Or it works very well by just bolting it up without the bracket. The holes line right up.

pete.v said:

Chris,
I don't know if you can get these over there but the Dynatec DC7-1 is a super solid 5ohm coil that works with all of these EI ignitions. Before the mag, I ran this for years with the Surefire. It is a Sherman Tank of a coil. I am sure the RGM is fine, but I know that this DC7 is awesome.

Click to expand...

I am sure that works fine, but as you said, it is a Sherman Tank of a coil, in the UK its twice the price of the RGM coil, but you really do seem to get twice as much coil

Which is exactly my problem with it....

SteveA said:

pete.v said:

Chris,
I don't know if you can get these over there but the Dynatec DC7-1 is a super solid 5ohm coil that works with all of these EI ignitions. Before the mag, I ran this for years with the Surefire. It is a Sherman Tank of a coil. I am sure the RGM is fine, but I know that this DC7 is awesome.

Click to expand...

I am sure that works fine, but as you said, it is a Sherman Tank of a coil, in the UK its twice the price of the RGM coil, but you really do seem to get twice as much coil

Which is exactly my problem with it....

Click to expand...

When I replaced a Boyer / Lucas coils set up with a TriSpark / Dyna coils on a highly tuned 988cc BSA triple I got an instant 5 BHP increase.

It helped to convince me that it is well worth investing in a whatever it takes to give you the biggest fastest spark you can get !

I too was scared off by the price of the RGM twin output coil, thinking it must be some cheap Chinese special. i bit the bullet and ordered one and when it came it was the exact same thing as the coils on my Bandit, (however not sure if these are the oem parts still.) I've had it fitted to the bike since Easter and it hasn't missed a beat, my biggest gain with it is that I can now remove my petrol tank front nuts in seconds, not having the twin coils bang in the way of them, the twin coil is under the middle of the coil bracket on a decent heatsink. Along with replacing the rear tank strap with a rubber ring I can do pit stop like tank removals, I'm almost ready for next years T.T. .
It was money well spent but you could get a secondhand Jap one from a breakers like a Bandit 600 to try out if it's the right price.