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Ignition coils for Grosset set up

minivin

Well Known and Active Website User
VOC Member
Quick question which may bring some wise solutions.

I have a twin spark F. Grosset ignition system on the Comet and unluckily I fitted Dyna coils before it become known they poss a problem. It would seem that they are now dying and I need to fit some 3.0 to 5.0 Ohm coils in their place.

What coils have other people used (single output is my requirement as I have a two-coil set up), and where did you purchase them?

Down to only a horrid Honda Benley to keep me on the road at present :( however it's more reliable than the BMW, Land Rover or Vinny:D
 

wparr2

Active Website User
VOC Member
Re:ignition coils for Grosset ignition

I've had problems with Dyna coils too!

So I fitted a Suzuki coil (Suzuki part no. 33420-48B00, this is actually a Denso coil 129700-1480), this had a resistance of 3.8 ohms.

And all is well for over 3 years.
 

Comet Rider

Well Known and Active Website User
VOC Member
Coils

Hi Minivin,

Both dad and I run 5 Ohm Dyna coils, mine with single output, and my dad's with twin output.
Mines been fitted for 4 years, and dad's for over 5 years, both without problems. Dyna do do a range of different primary resistances to suit all applications. I used to use Dyna gear on my drag racer, which ran fine for nearly 10 years without any problems. The only comment I will make is that the Dyna kit can be sensitive to voltage fluctuations.

Neil
 
D

Deleted member 1616

Guest
Boyer Branson's working for me too. Replaced a green one yugh.!. I can always cannibalize my Dyna in emergencies.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Coils

I used generic Japanese coils (Kawasaki I think) at 3.5 ohms. I had a lot of trouble with coils dying because, I thought, they had overheated if I left the ignition on. This happened when I stopped for fuel, changing the coil got me going again. (My coil is beneath the magneto cowl.) But when I took four coils to my local dealer to find out which one was the only one that worked, they all did. This made me think that perhaps I had another problem - but have no idea what it could have been. I was told that a modern ignition system would have a sensor that cut off the coil if no signal came through, but find it difficult to believe that coils could overheat in a few minutes.
 
D

Deleted member 1616

Guest
I had advice, can't remember where, not to mount under the cowl as it can interfere with the electronic unit and suffer heat problems. The instructions (see Forum article Which Electronic Ignition?) says 3-5 Ohm, plus mount to metal frame, I guess as a heat sink. Mine is mounted to the front cylinder head on an aluminum bracket.

I must admit, I'd like to know where else it could be mounted. The green Dyna one was mounted to the Alternator and look really ugly.

Martyn
 

Tom Gaynor

Well Known and Active Website User
VOC Member
cOIL MOUNTING

I mounted mine directly to the cowl (to use the cowl as a heat sink) and made a heat-shield to fit between coil and crankcase to help when there was no airflow. I remain unconvinced that coils designed to be fitted to Japanese fully-faired megabikes are so frail. Doesn't get me any nearer finding out what my problem was, though.

I had advice, can't remember where, not to mount under the cowl as it can interfere with the electronic unit and suffer heat problems. The instructions (see Forum article Which Electronic Ignition?) says 3-5 Ohm, plus mount to metal frame, I guess as a heat sink. Mine is mounted to the front cylinder head on an aluminum bracket.

I must admit, I'd like to know where else it could be mounted. The green Dyna one was mounted to the Alternator and look really ugly.

Martyn
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Grosset coil

Bruce: could I ask you to check that again with Glen? I was told by "a usually reliable source" that it didn't, but should have.
(If you were to think I was grasping at straws here, then you get 10 points. I am. I know people who have what on the surface is exactly the same set-up as mine, and when asked about coils say "Coils? What coils?")

Glenn Shriver has told me that his Grosset ignition has that feature.
 

bmetcalf

Well Known and Active Website User
VOC Member
Ask him yerself, he is in the UK, went to the Severn Rally. In fact, he's probably looking for you. Seriously, he has said it several times to me. Trevor of Hayling might know; also, there may have been more than one iteration by Francois.
 

roy the mechanic

Well Known and Active Website User
VOC Member
coils

Most electronic ignition systems instructions will tell you not to mount the coils near to either the trigger unit or the "black box". The reason is that the magnetic flux of the coil will "talk" to the electronicals and cause all manner of apparent faults. Some units will shut down when they "see" these spurious signals.
 
Last edited:

Chrish

Well Known and Active Website User
VOC Member
I have the coils where the MAGGI normaly sits, when the weather here is warm, and we do get warm, I can't tell the difference, this could be luck!!!

Chris
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Grosset spruiter

Don't be ridiculous Roy. The distributor (spruiter in Glaswegian - marvellous name) is French, the coils Japanese. How on earth can they talk to one another?
(Meantime: thinks.....)

Most electronic ignition systems instructions will tell you not to mount the coils near to either the trigger unit or the "black box". The reason is that the magnetic flux of the coil will "talk" to the electronicals and cause all manner of apparent faults. Some units will shut down when they "see" these spurious signals.
 

bmetcalf

Well Known and Active Website User
VOC Member
I asked Glenn about this auto-turn off feature and it appears it was a fantasy of mine. So, unlike the mighty magneto, it does have to be turned off. He pointed out that Francois has an advert in the May MPH and I could get the answer from la bouche de cheval, if I wanted.

Apologies for any inconvenience I may have caused. What other fantasies of mine are you going to expose?

Bruce: could I ask you to check that again with Glen? I was told by "a usually reliable source" that it didn't, but should have.
 

macvette

Well Known and Active Website User
Non-VOC Member
This isn't strictly on subject but it's related. I'm rebuilding an open series D which has coil ignition. I would like to mount a coil (or coils ) out of site under the distributor cowl. The bike has been fitted with a series C cowl at some time. I am retaining the 6 volt system. Anyone know which coil(s) would be suitable?
 

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