Airfan
Registered user
Is there any benefit in replacing the later BMW unit with one of these?
Thanks
Rob
Thanks
Rob
Dyna coil
- Thread starter Airfan
- Start date
If you mean one of these . . Then be aware that they are effectively 6v coils as they only have an internal resistance of 1.5 ohms. On a 12v system, one would draw 8 amps which is rather a lot for the ingition system (plus the coil will probably overheat).
They are usually mounted in pairs in a 'twin plugging' installation where they are wired in series like this . . giving a resistance of 3 Ohms and a current draw of 4 amps - which is the same as the standard coil.
I have fitted pairs of Dyna Coils to two 'twin-plugged' airheads and they work fine.
I am not aware of other Dyna coils intended for single use on 12v systems but they may well exist in which case I can't offer any further advice.
Happy New Year.
Bob.
Airfan
Registered user
Hi Bob, thanks for the comprehensive heads up. The reason I was asking is a guy on ADV rider fitted one to his ST. Apparently it's a kit supplies by Mottorad Electrik. He mentioned better starting, and it looked like a bolt in part.
http://www.motoelekt.com/ignition.htm
Cheers
Rob
http://www.motoelekt.com/ignition.htm
Cheers
Rob
D6
Registered user
used these a lot on jap bikes,unless highly tuned ,i noticed little difference,however, they recon your plugs run cleaner????.
Rob,
That's interesting, they are saying that a single 1.5 ohm coil can be fitted to the later Boxers. If I had seen the green and brown coils in a catalogue, I'd have gone for the green one at 3 ohms. Just shows how wrong one can be.
I have certainly had a standard BMW coil split and fail and if I recall correctly, the new replacement was around £80. One of these might be cheaper.
I also found that I got better starting after converting my 1988 R80RT and 1989 R100GS to twin plugs - but I put that down to having twin sparks and two new coils. Maybe just replacing the coil will also give an improvement.
Depending on your bike, a single brown coil might be worth a try.
Let us know how you get on with it.
Bob.
Airfan
Registered user
Thanks.
Interesting; but I am still slightly uneasy about fitting a 1.5 ohm coil.
Something in the electronic ignition triggering circuit may be providing sufficient resistance to reduce the current through the coil (which is intermittent, admittedly).
However. 1.5 ohms in a 12v circuit = 96 watts.
You have a 240 watt alternator (unless you have a 400 watt conversion ?).
Headlamp + rear light + sidelight + instrument light = around 75 watts.
Indicators & brake light = 63 watts.
Heated grips ?
Plus it would be nice if the battery got charged as well.
Its a bit of a balancing act if you brake & indicate a lot.
I would be interested to know what the ignition circuit current is when its running as it may not actually be a problem in reality.
I'll be interested to hear how you get on.
Best of luck.
Bob.
96 Watts
Bob, dont forget that the current is not flowing through the coils all the time so the power needed is nothing like 96 Watts.
I am sure that someone here will be able to give you a good estimate of the average power used by an ignition system using 1.5 Ohm coils
Nick
Bob, dont forget that the current is not flowing through the coils all the time so the power needed is nothing like 96 Watts.
I am sure that someone here will be able to give you a good estimate of the average power used by an ignition system using 1.5 Ohm coils
Nick
slightly off topic / but maybe useful info 
on my Guzzi (Cali3) i've replaced the ignition unit twice (dont ask!
).
after the oe "Motoplat" unit i had a "Rita".
not bad, no improvements on starting, running or performance.
now i have a DYNA unit fitted. but not the Dyna coils.
starts easier, more powerful spark, cleaner plugs and seems to have a little more power - though maybe thats imagined
by optimistic owner!
as soon as finances allow i want to put the Dyna coils on too - it runs with spurious car coils at the moment which work fine / but i'd like to match the unit with suitable coils, so i imagine
its worth the money.
damn thing STILL eats plugs on the right hand pot though. they just die after approx 2500miles. replace with a new one at it runs grand again..... i've never managed to figure out why
on my Guzzi (Cali3) i've replaced the ignition unit twice (dont ask!
).after the oe "Motoplat" unit i had a "Rita".
not bad, no improvements on starting, running or performance.
now i have a DYNA unit fitted. but not the Dyna coils.
starts easier, more powerful spark, cleaner plugs and seems to have a little more power - though maybe thats imagined
by optimistic owner!as soon as finances allow i want to put the Dyna coils on too - it runs with spurious car coils at the moment which work fine / but i'd like to match the unit with suitable coils, so i imagine
its worth the money.damn thing STILL eats plugs on the right hand pot though. they just die after approx 2500miles. replace with a new one at it runs grand again..... i've never managed to figure out why
Airfan
Registered user
I contacted Rick at Motorrad Electrik, and he kindly replied, and allowed me to post his reply here.
Hi Robin,
The questions about the RIGHT coil(s) for BMW twins come up often, accompanied by much incorrect information. Use this posting as you see fit :
There really is no such thing as a 6 volt or 12 volt coil , they are really just marked that way for convenience. The coil is just that, a couple of spools of wire that carry current. Coils are , however, engineered to have characteristics ( primary and secondary winding resistances ) that are best suited for a particular type of ignition system. Note that even different types of electronic ignitions have different coil requirements, just like points vs. electronics, etc. When the original resistance requirements are significantly changed, problems will likely result.
For air-cooled BMW motorcycles here are the coil requirements for primary winding resistance :
1970 - 80 models with points ignitions use two 1.5 ohm coils wired IN SERIES, to achieve a total primary resistance of 3 ohms. Yes, they're marked 6 volt and are used on a 12v system.
1981 - 92 models with factory Hall - effect design electronic ignition can have either two 0.72 ohm coils in series, or a single-unit coil with 1.5 ohms resistance.
1993-95 models with updated coil and ignition module have a single-unit coil with 0.7 ohms primary resistance. The new coil has a yellow-cadmium plated steel mounting bracket, reddish-brown plug wire towers, and the control module has light blue lettering on it.
This change was likely to have been as much a matter of convenience to use an off-the-shelf part already used on other models, as it was to address the very high failure rate of the original one-piece coils .
BMW says the new coil _must_ be used only with the new module, but I have seen many cases of an improper mix with no failures. The new module retrofits all bikes back to 1981 with a 1.5 ohm coil . This is the only coil / control unit now sold by BMW.
The Dyna 1.5 ohm single coil with 2 outlets is the correct one for all 81-95 models . I have sold many hundreds of them through the years, and they will work very reliably as a replacement part option .
Cheers, Rick
Hi Robin,
The questions about the RIGHT coil(s) for BMW twins come up often, accompanied by much incorrect information. Use this posting as you see fit :
There really is no such thing as a 6 volt or 12 volt coil , they are really just marked that way for convenience. The coil is just that, a couple of spools of wire that carry current. Coils are , however, engineered to have characteristics ( primary and secondary winding resistances ) that are best suited for a particular type of ignition system. Note that even different types of electronic ignitions have different coil requirements, just like points vs. electronics, etc. When the original resistance requirements are significantly changed, problems will likely result.
For air-cooled BMW motorcycles here are the coil requirements for primary winding resistance :
1970 - 80 models with points ignitions use two 1.5 ohm coils wired IN SERIES, to achieve a total primary resistance of 3 ohms. Yes, they're marked 6 volt and are used on a 12v system.
1981 - 92 models with factory Hall - effect design electronic ignition can have either two 0.72 ohm coils in series, or a single-unit coil with 1.5 ohms resistance.
1993-95 models with updated coil and ignition module have a single-unit coil with 0.7 ohms primary resistance. The new coil has a yellow-cadmium plated steel mounting bracket, reddish-brown plug wire towers, and the control module has light blue lettering on it.
This change was likely to have been as much a matter of convenience to use an off-the-shelf part already used on other models, as it was to address the very high failure rate of the original one-piece coils .
BMW says the new coil _must_ be used only with the new module, but I have seen many cases of an improper mix with no failures. The new module retrofits all bikes back to 1981 with a 1.5 ohm coil . This is the only coil / control unit now sold by BMW.
The Dyna 1.5 ohm single coil with 2 outlets is the correct one for all 81-95 models . I have sold many hundreds of them through the years, and they will work very reliably as a replacement part option .
Cheers, Rick
That's interesting, thanks for clearing up my confusion.
It does raise another question, though.
I am using a pair of 1.5 ohm Dyna Coils on a 100GS - wired in series. Should I put these in parallel as the electronics seem to handle the load ?
Some background:
When I twin-plugged my R80RT, I used a pair of coils supplied by Motobins.
I made up a mounting bracket and wired them in parallel.
The bike ran, but not well.
I contacted Motobins who advised that they should be wired in series. I changed the wiring and immediately had problems. Investigation showed that one coil was 'open circuit'.
I didn't like the coils or their fittings and as I suspected that I had fried them by running them at 12v I bought a pair of Dyna Coils from MotorWorks, wired them in parallel and have had no trouble since.
That is why I have been a bit wary about adding non-OE coils.
The Motobins coils looked like this:
I'll keep my pair of Dyna coils wired in series unless someone can advise otherwise.
Thanks again.
Bob.
It does raise another question, though.
I am using a pair of 1.5 ohm Dyna Coils on a 100GS - wired in series. Should I put these in parallel as the electronics seem to handle the load ?
Some background:
When I twin-plugged my R80RT, I used a pair of coils supplied by Motobins.
I made up a mounting bracket and wired them in parallel.
The bike ran, but not well.
I contacted Motobins who advised that they should be wired in series. I changed the wiring and immediately had problems. Investigation showed that one coil was 'open circuit'.
I didn't like the coils or their fittings and as I suspected that I had fried them by running them at 12v I bought a pair of Dyna Coils from MotorWorks, wired them in parallel and have had no trouble since.
That is why I have been a bit wary about adding non-OE coils.
The Motobins coils looked like this:
I'll keep my pair of Dyna coils wired in series unless someone can advise otherwise.
Thanks again.
Bob.
daytonatwin
Registered user
Some jap bikes, such as the honda CBR 600 have dual output coils. They are, totally reliable. I have one fitted to my 1973 Triumph 500 Dayona.
I bought it from the local breakers yard (Blacks of Burscough) for far less than you would if you bought new. So it might be worth looking into. Also they are so compact, you can fit them anywhere.
I bought it from the local breakers yard (Blacks of Burscough) for far less than you would if you bought new. So it might be worth looking into. Also they are so compact, you can fit them anywhere.
alimey4u2
Registered user
Dyna S recommend that you increase the plug gaps by 25-50%. I have been running this setup (Green ones, dual output with Dyna S pulser) on my Honda for over 20 years & the system has been flawless.... One helluva spark by the way....
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