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1Back to top Go down   BMW K100 Coil Ohm Values Empty BMW K100 Coil Ohm Values Fri Jan 01, 2021 7:31 pm

cycleman

cycleman
Silver member
Silver member
Not hard to tell it is winter in this neck of the woods.

Doing some searching on this site I have found some information on the coils, but it is scattered and actually doesn't totally address the topic. I also checked the Electrical Trouble Shooting Guide to see what it has for information. I haven't been able to find any information from BMW concerning what values should be on a new coil. It is pretty clear that the coil should have a certain primary ohm value to work properly with the ignition system and not cause harm to the computer/ignition electronics.

What I have found so far ( based on the troubleshooting guide on this forum ) is that on a K100 2 valve the primary ohms value was quoted as 2.6 ohms. The secondary was 12.6 K Ohms. This doesn't say if it is off the black coil, the grey coil or the newest coil with the red tips, new or used coil. So what I'm asking is for anybody that is interested to please provide readings that you might have. In your reply give the year of bike, build date if you have it, 2 V or 4 V, colour of coil, secondary readings if you have them and new or used coil. I realize the coils/ignitions are totally different between the 2 & 4 valve versions, but it might help somebody dealing with an ignition issue on one of these bikes.

My example. 1986 K100RT Feb/86 build date, grey coils, primary 2.3 ohms on both coils. No secondary reading as I didn't remove the coils. Bike runs fine, no ignition issues, plugs fairly new, original plug wires, original coils, bike has approximately 19,000 miles/31000 kms.

Thanks for your input.

    

2Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Fri Jan 01, 2021 7:55 pm

Two Wheels Better

Two Wheels Better
Moderator
Moderator
90,000 mile/145,000 km black Bosch coils with brown tips, 1987 K100RS, the resistance measures (between the 2 high voltage terminals) 12.61KΩ and the primary coil measures 2.6 Ω.


__________________________________________________

1970 R60/5, OZ '77 R75/7-R100, '85 K100'87 K75C, OZ '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R'04 R1150RT, '05 K1200S, '06 K1200R, '07 K1200R, '09 K1300GT & 2013 R1200RT-Polizei  - Beemers owned still or sold.

~We all believe what we want to believe in - Rob Dickinson
    

3Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Sat Jan 02, 2021 12:15 am

RicK G

RicK G
admin
admin
All the coils for 2 valve K100 should be the same and when measuring check that there is no electrical connection between the HT and primary coil and also either winding and the centre core. Even a few meg ohms means there is a break down of the insulation and failure is not far off.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

4Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Sun Jan 03, 2021 6:31 pm

cycleman

cycleman
Silver member
Silver member
Ignition Off. OK I went out to the garage today and measured the coils again. I unhooked the primary wires and found the same reading 2.3 ohms for both coils primaries. I hooked the primary wires back up and then unplugged the plug wires for each coil and measured the secondaries. Coil # 1 first coil in the pair - measured 10.14 K ohms, Coil # 2 measured 10.02 K ohms. Also it would be nice to see some readings from the older coils black or grey as maybe they where all like that and that is why they changed them out on the later K100 2V.

Both primaries and secondaries are a bit low from the 2.6 and 12.6 Ohms ( from troubleshooting guide ). So is that the gold standard for these coils and what the readings must be or is there a tolerance range. I see the coils shown with these readings is a 4v coil ( used in the troubleshooting guide on this forum ). I know the 2V & 4 V coils are not interchangeable. So is there a different primary & secondary resistance value with the 2 V coil.

As a general comment on coils, anything I've read generally says that the primaries should be between .5 - 3 ohms and secondaries  6-12,500 ohms. This depends on the ignition system of course, points/electronic etc.

I would think that a 3 ohm aftermarket coil would work fine. Any of the others from Dynatek have too low of ohm value. Any thoughts.

    

5Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Mon Jan 04, 2021 12:55 pm

cycleman

cycleman
Silver member
Silver member
This was from a 2014 post. Bike was a 1989 K100 not sure if a 2 v or 4 v, but it looks like a 2 valve model.

" Thanks for that Rick
Just to confirm, I have the black coils with the brown towers. I think they are the original coils??

Leads (1) 5.32kΩ  (2) 5.06kΩ  (3) 5.17kΩ  (4) 5.36kΩ

Coil 1/4 - Prim: 2.2Ω  Sec: 11.92kΩ   (No earth leakage)

Coil 2/3 - Prim: 2.3Ω  Sec: 11.83kΩ   (No earth leakage) "

That's just about the same as my 86 coils. So it would seem there is a bit of a ohm resistance range for these coils to operate in.

    

6Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Mon Jan 04, 2021 11:28 pm

Laitch

Laitch
Life time member
Life time member
@cycleman wrote:Bike was a 1989 K100 not sure if a 2 v or 4 v, but it looks like a 2 valve model.

". . . Just to confirm, I have the black coils with the brown towers. I think they are the original coils??
Coil 1/4 - Prim: 2.2Ω  Sec: 11.92kΩ . . .  
Coil 2/3 - Prim: 2.3Ω  Sec: 11.83kΩ . . ."
 
That's just about the same as my 86 coils.
The '89 coils had values 94% of the benchmark values in the troubleshooting guide. Your '86 coils had values 80% of those benchmark values. Those wouldn't seem "just about the same." Nevertheless, the values in this extract from the arcane but ever-popular BMW Diagnose—Testing Instructions for K Models seem to suggest more possibilities. Smile  

BMW K100 Coil Ohm Values Scree120

You'll be revered for your pioneering work with Dynatek coils. cheers Exactly which model were you considering?


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1995 K75 81,000 miles
BMW K100 Coil Ohm Values Usa-lo10
    

7Back to top Go down   BMW K100 Coil Ohm Values Empty Re: BMW K100 Coil Ohm Values Tue Jan 05, 2021 10:10 am

cycleman

cycleman
Silver member
Silver member
Thanks for that and that should be in the resources folder for these bikes. That is an interesting chart and shows that my coil values both primary & secondary are spot on. The plug wires are also in the range of 4.8 K - 5.3 K so I think I'll spend my money elsewhere. I'm pretty sure the coil shown in the trouble shooting guide is for a 4v as the primary connectors are different than on my 2 v units, and that could explain the slight difference in resistance.

As to Dynatek coils. I was going to go with the 3 ohm version, green in colour, Model DC1-1. They make two versions with slightly different angles on where the plugs wires connect and this one likely would be the easier to adapt. The other version DC6-1 would be harder to adapt. The first version would be easier to use the existing stock mounting bracket, just drill out the old coil mounting rivets. The BMW coils are rubber mounted, so to use the Dynatek you would have to add a ground to the mounting bracket.

BMW couldn't have found a hotter place to mount the coils, I'm not sure what they were thinking.

    

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