Author Topic: 1984 K100 coil options  (Read 1283 times)

Offline GaryFrank

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1984 K100 coil options
« on: July 08, 2019, 06:42:31 PM »
Hi all

I'm wondering what my options are regarding ignition coils.
P.O suspected a faulty coil and tried to fit a Ford Focus coil pack (hence the burnt wires)

I've read on another forum that it does work and am asking if anyone here has tried anything similar.
I know that OEM would be the best option but am working with Monopoly money (15:1)

Thanks
  • Cape Town
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Offline Scott_

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Re: 1984 K100 coil options
« Reply #1 on: July 08, 2019, 10:13:56 PM »
Unlike the K75 that uses 1 coil per cylinder, the 4 cylinder bikes utilize coils that have 2 HV outputs on each coil that both fire at the same time(wasted spark design)..... Can't say as I have heard of any auto application ignition coil that is the same configuration.....
Personally I wouldn't waste my time or limited money on something that would be a "maybe" resolution, and rather spend it on the correct OEM solution and not wonder how long it might last..... Try and find yourself a good used one, if your sure that is the issue. Depending on your problem, it could be the ignition amp that is causing issues and not a coil.... Check and make sure the heat sink paste is fresh and not dried up on the backside of the amplifier module, not uncommon as the bikes age and some owners don't think about it.
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Offline The Mighty Gryphon

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Re: 1984 K100 coil options
« Reply #2 on: July 09, 2019, 09:59:08 AM »
I agree with Scott that getting the correct coil is the way to go.  The early coils had issues that were corrected in later units.  If you can find used K100 coils from an '87 or later you should be in good shape. 

In the years I have been hanging around these forums I've seen a fair number of riders change out those old coils for the newer design with excellent results.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
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'91 K100RS "Moby Brick Too
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Offline JPaganel

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Re: 1984 K100 coil options
« Reply #3 on: July 10, 2019, 12:53:43 AM »
Unlike the K75 that uses 1 coil per cylinder, the 4 cylinder bikes utilize coils that have 2 HV outputs on each coil that both fire at the same time(wasted spark design)..... Can't say as I have heard of any auto application ignition coil that is the same configuration.....

Lots of automotive 4-cylinders do it. GM for sure. But the coils are usually in an inconvenient large plastic box.
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #4 on: July 25, 2019, 03:11:37 PM »
Okay, so Iíve replaced all the burnt wire and fired her up.
Missing on number 3 plug. Switched 2 & 3 plug wires On the coil and the miss moves to plug 2.
Coil is definitely toast but the replacement cost is stupid.

This leads me to an alternative- Ford Focus also fires 1 & 4 (wasted spark)
The only possible problem I can see is that the Ford unit has a low impedance - 1,2 ohms.
Will this eventually kill my ignition unit ?
Are there any options as in firing an in-line amplifier ( or summat to that effect)???
  • Cape Town
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #5 on: July 25, 2019, 03:17:15 PM »
Said Ford coil....
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Online daveson

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Re: 1984 K100 coil options
« Reply #6 on: July 25, 2019, 03:50:49 PM »
The problem followed the wire,  hopefully the coil is good and it's only a bad wire.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #7 on: July 25, 2019, 03:52:12 PM »
Nah, not so lucky..... itís definitely the coil
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #8 on: July 25, 2019, 04:12:28 PM »
From our friends at Summit Racing:


ďSo, less resistance is better, right? No. Not always.

If the resistance is too low, the added current could damage the distributor points or the electronic ignition module. When shopping for a coil, make sure the primary resistance is compatible with your other ignition components.Ē

Has anyone come up with a solution.....in-line amp of sorts
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Offline Laitch

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Re: 1984 K100 coil options
« Reply #9 on: July 25, 2019, 04:24:27 PM »
Missing on number 3 plug. Switched 2 & 3 plug wires On the coil and the miss moves to plug 2.
Did you inspect the faulty terminal coils terminal for corrosion?
I've read on another forum that it does work and am asking if anyone here has tried anything similar.
What was used for a successful coil substitute in the post on other forum?
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #10 on: July 25, 2019, 04:39:37 PM »
I did inspect the coil in every direction ( this was the original problem which led to the POís diy wiring burn-out)

Other site mentioned a Ford Mondeo coil pack and stated that it works, but makes no mention of leaks no term effects. I have also spoken to a local (South Africa) who has run on the Ford coil but changed back to original...

I will wire up the Ford coil tomorrow just to run her on all 4, but will keep on digging till I find a cheaper solution.
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Online daveson

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Re: 1984 K100 coil options
« Reply #11 on: July 25, 2019, 04:47:59 PM »
How did you decide it's not the wire?  Are all four wires the same brand and type?
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #12 on: July 25, 2019, 04:53:10 PM »
Sorry, I didnít mention that I had partially rewired the bike.
All the coil wires, right handlebar switch, ignition switch, front brake switch.....
Iím still looking for a right handlebar switch - have ďhotwiredĒ everything needed to get her running
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #13 on: July 25, 2019, 04:54:57 PM »
Plug leads are brand new
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Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #14 on: July 25, 2019, 04:58:32 PM »
I did inspect the coil in every direction ( this was the original problem which led to the POís diy wiring burn-out)

Other site mentioned a Ford Mondeo coil pack and stated that it works, but makes no mention of LONG term effects. I have also spoken to a local (South Africa) who has run on the Ford coil but changed back to original...

I will wire up the Ford coil tomorrow just to run her on all 4, but will keep on digging till I find a cheaper solution.
  • Cape Town
  • K100 RS

Online daveson

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Re: 1984 K100 coil options
« Reply #15 on: July 25, 2019, 05:04:25 PM »
It's rare, but sometimes new stuff is faulty,  which mondeo engine and year have you used.?

Let us know the results if you end up running with the mondeo coils.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #16 on: July 25, 2019, 05:14:51 PM »
Will play some more tomorrow.
I have no doubts about the Ford coil pack working, Iím just concerned about the long term effect (1,2 ohm coil resistance)
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Offline The Mighty Gryphon

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Re: 1984 K100 coil options
« Reply #17 on: July 25, 2019, 10:03:16 PM »
I wonder what the availability of used later model K100 coils is like in S.A.  That is  the route I would go.  Early coils had problems, later model coils are a lot more reliable.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline johnny

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Re: 1984 K100 coil options
« Reply #18 on: July 25, 2019, 10:15:43 PM »
greetings...

there is a bike breaker in south africa that has brick parts...

there was a motobricker here a few years ago from south africa and chronicled his drama scoring parts...

i will have to think about it later because im exhausted from unwhacking tommyts whack...

j o
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Offline Laitch

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Re: 1984 K100 coil options
« Reply #19 on: July 25, 2019, 10:25:28 PM »
Will play some more tomorrow.
I have no doubts about the Ford coil pack working, Iím just concerned about the long term effect (1,2 ohm coil resistance)
It could overheat the electronic control unit resulting in its failure but there might be used control units available, maybe at the bike breaker j o has indicated.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #20 on: July 26, 2019, 04:03:54 AM »
I found a pair of orange tops on eBay for GBP30. Number 2 son is getting them for me 👏👏👏

Still gonna connect the Ford unit just to fire her up and check everything, then Iíll strip her down and make pretty. 
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Online daveson

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Re: 1984 K100 coil options
« Reply #21 on: July 26, 2019, 04:38:06 AM »
Do you want to use Focus coils like the PO did?
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline GaryFrank

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Re: 1984 K100 coil options
« Reply #22 on: July 26, 2019, 04:39:50 AM »
I donít think he knew what he was doing - electrickery isnít for everyone
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Online daveson

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Re: 1984 K100 coil options
« Reply #23 on: July 26, 2019, 04:40:55 AM »
"P.O suspected a faulty coil and tried to fit a Ford Focus coil pack (hence the burnt wires)"

In reply #4 you say you want to put Focus coils in.

Huh ...hang on...  wait...  what?

Am I missing something?
  • Victoria, Australia
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Online daveson

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Re: 1984 K100 coil options
« Reply #24 on: July 26, 2019, 04:45:06 AM »
Oh, OK.

I'm wondering why the other bloke who tried them went back to the originals.

Somehow I can't attach quotes properly anymore,  it just turned into multiple posts.

Anyway let us know the results please.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

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