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1Back to top Go down    1984-85 K100 ignition coils on Thu 13 Jun 2013 - 11:53

brickrider

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Recently a BMW mechanic of many years told me the earlier K100 bikes had issues with the ignition coils. He said the earliest examples failed frequently (something to do with the part no. being stamped on the coil body) and even the second generation being low quality. He further recommended I fit coils from the K1100 series motors. Has anyone else heard of this? As I was about to begin a long tour, I asked the mechanic if he thought this would pose a reliability problem (I was to ride though some very desolate country). He replied I'd probably be ok, but my mpg would not be very good due to weak spark.
Well, I'm home again without any roadside repairs needed on my bike, but the mpg was not what I'd hoped for. My buddy's R1100RS (oilhead) was consistently less thirsty than my 1985 K100RS.

    

2Back to top Go down    Re: 1984-85 K100 ignition coils on Thu 13 Jun 2013 - 12:21

RicK G

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Firstly the fuel consumption of a twin of similar capacity will always be better, a multi cylinder is not as efficient in that regard as a twin.
There are two types of coil for the K100 and can be distinguished by the lead mounts. The early types that were not of low quality but didn't stand the test of time were all black where the later model coils had a red/orange mount where the spark plug leads plug into them.
You could use the K1100 coils but they are not any better than the later K100 coils and you will need to modify the wiring harness where the wires plug into the coil and put new plug leads as they aren't the same and the plugs you use are also different (D7EA for K100 and DR7EA for K1100)
There is no reason at all to use the K1100 coils over the later K100 coils.
If you have the early all black coils then replacing them is a good idea as they do frequently give trouble.
If your bike has been active all its life then there is a good chance it has the later coils already.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

3Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 3:41

brickrider

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If I understand you correctly, the old coils need non-resistor plugs, the newer (K1100) require plugs with resistors? The mechanic who advised me to change the coils never mentioned that.
Isn't it possible to use a resistor, if required, anywhere in the system? For example, it could be in the spark plug itself, or in the "cap" that fits over the plug.

    

4Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 5:28

charlie99

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just for clarificaition on the older coils
if you have copper cables you could benefit from resistor type plugs . or resistive plug tops, but never both should be used

most cables these days have some resistance inherant to them ...such as silicon types and the newer versions and variations of the same andstock oem bmw leads (about 8-10 k per metre)

the idea is to limit the resistance values from high voltage post of the coil to tip of spark plug electrode to about 5 k total on each leg
this use of resistance is to comply with emi (rf noise ) regulations ...and is generated by the ignition pulseof rf into the air which affects any radio receiver nearby . by limiting the spark current the rf is significantly reduced .

many of us remember the older 60s era vws that you could hear comming past on your radio receiver, which was verry common

further to that
if you happened to fit resistive plugs and resistive leads you could well damage the coil .
when the coil fires you are actually firinga pulse to each of the spark plugs that share the coil
thatpulse is limited in its amplitude by the loading (resistance ) of the ignition lead to spark gap and earth .
so if you have higher resitance in the leads you will have less spark energy available at the plug .

if you happen to have more resistance than say 10k in each leg of the ignition coils ,the terminal voltage produced bythe coil is excessive , as lighter loading (or higher resistance ) to let the pulse disapate willcause a higher terminal voltage across the coil.
this could cause cross firingof the coil secondary between layers internally, eventually causing failure of the coil pack (see pic below).
likewise if you have poorly connecting plugtops and orcoil connections, this effect could likely cause a failure long term .

in each case above you will have lower available spark energy available at the spark gap ...causing lower power to the motor (or the effective ignition spark and air- fuel charge burn )

note if you have just one lead connection issue it will reduce the effectiveness of spark to both cylinders connected to the same coil
for some this might not be immediatly noticeable , especially on frequent short trips . but the results are self evident .

here are a couple of coils imported from uk ,,,still operational but no measureable resistance from one high volt tower to the other


could this explain why these coils are in a "sell off" (part out) of a k ....that performed poorly ?

in any case it seems to me that these coils we remooved from a poorly maintained system , and possibly corrosion affected by the wet road conditions experienced over there .

i believe the red top coils measure differently to the all black

the red top coils about 12.6 k whilst the black about 10.2k on the secondarys


secondary primary



from the circuit above you can see that if you add any resistance to either of the leads it will affect the whole circuit involved as there is no other earth reference.... in differenceto a high number of conventional car type systems where the secondary of the coil is effectivly earthed and each lead (through distributor) is treated as individual .



hope that helps



Last edited by charlie99 on Sat 15 Jun 2013 - 5:40; edited 3 times in total


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

5Back to top Go down    Agreed with rick on Sat 15 Jun 2013 - 5:32

ibjman

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I agree, The upgraded coil with the orange towers fixed a myriad of issues on my 85.
Also something that may not have been mentioned earlier unless I missed it is: even if you did elect to change all the wiring ends needed to connect the 1100coils to the early machine, they are the incorrect primary resistance for the design of the early ignition control unit.
Various opinions have been ventured as to what would occur by using them.......some say the excess draw of the lower resistance primaries would overload the circuit in the module that is not designed for it.

As to spark plug/Ignition wire resistance: The early bike has a 5000~ resister built into the metal cap end at the spark plug. It has non resistor wire and non resistor plugs.
I have no knowledge of what the 1100 comes with but it's not prudent for your use anyhow.

I'm not sure what you currently have or have not installed at this time.

Suggest you return to te stock configuration as mentioned above before attempting to address any thing else.
Regards, Ibj...

    

6Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 6:06

charlie99

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Lower impedance primary coils on the early series ignition systems would also have a greater back emf voltage spike that might just tip the ecu over and short it out .

there was a big moove on second gen systems (industry wide) that mooved to lower resistance primary coils ....for what reason still amazes me ...but might have something to do with economising on coil production and size ...the inherant higher currents meant that many took the switching devices offboard the ecu ...and meant there was an "ignition amplifier module" added to the system


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

7Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 10:20

brickrider

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"I'm not sure what you currently have or have not installed at this time."

My motorcycle's coils are entirely black, so they no doubt are the suspect items. Shocked

    

8Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 10:40

RicK G

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I would certainly be planning at least to put the newer type on in the very near future.
To change to the K1100 type is not something I would not even consider as there is no advantage to be gained over the newer type K100 coils.
The only reason that I can see BMW changed the coils from the K100 is so that they could not be easily used in place of the K1100 coils because of the different ICU and damage that could occur.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

9Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 10:57

charlie99

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as long as the leads and connections are maintained well ...I don't see any issues other than environmental ..or locality differences that might affect build up of crud and thus some corrosion . well perhaps including rough treatment

could be a good idea to do the tests every season before starting off ?

for us lot down here I suspect we have a slight advantage of no salt on the roads during the winter - cold months ...but its good to know the differences of what might be available no ?


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

10Back to top Go down    There are 2 kinds of early K100 operators on Sat 15 Jun 2013 - 14:54

ibjman

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There are 2 kinds of early K100 operators:

Those who have the original black tower coils.......and are destined to spend countless hours tearing their hair out trying to find the elusive problem with drive ability caused by their weak/failing Original coils........

And there are those who have already installed the better orange topped ones and are blissfully motoring trouble free down the road of life!

    

11Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 20:47

K75cster

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Charlie, how is the damage caused with an unmatched set of leads is it in the secondaries that the issue arrises? being that we all should ensure as close a match as possible impeadence value to each plug.


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Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

12Back to top Go down    Re: 1984-85 K100 ignition coils on Sat 15 Jun 2013 - 23:02

charlie99

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yes indeed keith

the energy produced from the transfer of the pulse from the primaryto the secondary (read change in state from no current to high current and visa versa )
the high voltage has to dissipate somehow ....if we restrict the current going from the output terminals to a different and now reasonably low rate (towards the earth )a high potential still exists across the secondary coil for a slightly longer time . that high energy spikemay jump the coil layers if this builds up too much without being released ...in the long term causing an arc-carbon track to appear along that path .
now because that path is setup strange things occur .
multiplevoltage spikes are producedwhile the coil is still ok but increasingly the effectivelyshorted turns starts to be counter productive to the energy output production
this has more to do with the dielectric between the windings on the coil former (and insulation of the wire )
there have been a number of ways to counteract this ...namely to install a better insulatorbetween each layer of coil winding at time of manufacture ...but for the most case "we have what we have" to deal with .
the later series of coils may have been designed better ...especially after feedback of the failures noticed on earlier released product .
as with all electrickery as one end of the output pulses high the other end pulses low in relation ... draw a sine wave
and invert it for the opposite end of the coil
if we had a mismatch between resistance to earth (for want of a better description ) between one end and the other the amount of pulse energy release is still restricted by the total resistance of the circuit ...but in a weird way
since we are now dealing with ac circuits (waveform changing from positive to negative as the spark field is created , (resonance of the coils, ringing of the coil ,dwell etc etc ) the product of the current release becomes a different version of power factor in this case power output becomes "I" squared x ""R" so for every little difference of resistance the current disproportionally decreases to the higher resistance end of the output so you end up with a high going spike out one end matched by a restricted low negative going spark at the other end until the polarity changes in a half a millisecond or so...I better stop, its doing my brain in .....giggles

all too far complex to do anything about, but keep design specs and good working conditions in place for as long as you can, to ensure good reliability . which is remarkably easy to do ..if we take the time to lookand fix anything that is abnormal . its called maintenance and is far too easy to ignore .
we change our oil every five to tenthousand ks ...but has anyone pulled the plugs and leads to check in the last year ?


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

13Back to top Go down    Re: 1984-85 K100 ignition coils on Sun 16 Jun 2013 - 1:55

brickrider

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Well Charlie, that certainly clears things up !What a Face My "take away" from your very complete explanation is that, if I don't replace those coils, I'm apt to find myself standing on the side of a desolate Nevada highway yet again! (I've been trying to ride to New Mexico for two years running. Both attempts ended in failure in the middle of nowhere!)
Those coils are none too cheap, but Euromotorelectrics seems to have the least painful prices for them. However, I'm certainly open to other suggestions.
Anyone?

    

14Back to top Go down    Re: 1984-85 K100 ignition coils on Sun 16 Jun 2013 - 2:01

charlie99

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why so brick ?
does your leads and coils not measure correctly ?

you could go the cheep way and buy the standard accessory leads from any car store ....but look at realm engineering they have great leads as a set for really good prices


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

15Back to top Go down    Re: 1984-85 K100 ignition coils on Sun 16 Jun 2013 - 3:38

japuentes

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brickrider wrote:Well Charlie, that certainly clears things up !What a Face My "take away" from your very complete explanation is that, if I don't replace those coils, I'm apt to find myself standing on the side of a desolate Nevada highway yet again! (I've been trying to ride to New Mexico for two years running. Both attempts ended in failure in the middle of nowhere!)
Those coils are none too cheap, but Euromotorelectrics seems to have the least painful prices for them. However, I'm certainly open to other suggestions.
Anyone?

Hi there, I got mine from rockauto.com.
They dont sell it as a motorcycle spare, but searching by part number (0221500202) their catalog shows them.
Hope this helps
Best regards
JAP


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1988 K100RS SE/ABS
    

16Back to top Go down    Re: 1984-85 K100 ignition coils on Sun 16 Jun 2013 - 8:18

rosskko

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I had a failure in one of my coils, but it was the casing that failed.
The spark was coming out the side and arcing on the metal band that runs top to bottom on the coils.
Replaced with the orange top model and not a problem since.

rosscorossco


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1986 K100RT VIN 0093801K100RT with summer fairing for a northern visitor

Basic/2 6308802K100CJ05/1988

K1100RS 0194321
    

17Back to top Go down    Re: 1984-85 K100 ignition coils on Tue 18 Jun 2013 - 12:25

K75cster

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Thanks Charlie, will check all of mine the 3 and the 4 cylinder bikes, i receintly replaced a coil pack on my hyundai Lantra 1998ish because it was sparking from the post to the retaining bolt, perhaps it was a resistence issue causing it to take another somewhat shorter path, because i hadn't done enough maintanence on it, wonder if the coils would work on a K100. they're both wasted spark systems. So from what you write its really a good idea to get the pathway from the coil post to the centre electrode of the spark plug as equal as possible for the 1,4 and 2,3 sets and as conductive as possible a connection of the sparke plug to the engine to ensure a long life of the coils or at least cull any easy way for the coil to take a break from its duties.


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

18Back to top Go down    Re: 1984-85 K100 ignition coils on Tue 18 Jun 2013 - 18:07

charlie99

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good idea keith
the spark from the coils is truly a brutal thing .....what im mostly concerned about and try hopefully to remind folks that, firstly ...to have a look ......if they see a marked difference ...do something about It ....4k on one and 5k on the other is not a significant a difference when you consider that there is 10 to 20 something thousand volts trying ...as you say ...to look for the shortest route to earth .
I saw in here recently someone with 8 k on one and 4 k on the other ....of the pair which is certainly is an alarm bell for me .
and others with resistive leads in addition to the resistive plug tops or resistive plugs .....at least one noticed some significant change after doing a bit of a change ...
just a heads up again for some ol mate ....sparks jumping is not a good sign .


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

19Back to top Go down    Re: 1984-85 K100 ignition coils on Thu 2 Apr 2015 - 8:25

brickrider

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I took the suggestion of JAP (post #15 of this thread) and bought new coils to replace the original old style fitted to my 1985 K100RS. During a recent tour of some 2000 miles there were times when the engine seemed to be firing on two cylinders momentarily. I believe it was an electrical issue, as there was at least one gallon of fuel in the tank at those times of poor running, and the fuel pump and filter are quite new. On the tour I changed out the spark plugs for another set of NGK non-resister types, but the intermittent miss recurred. Back home, I measured the secondary ignition wires and the resistance in the coils. Nothing out of spec there. I examined the electrical connections to the pump, both inside the tank and at the under tank connector block. Nothing suspect there. I then measured the original coils and discovered that there is no measureable resistance in the secondaries however, the primary resistance is very close to spec. Those coils preformed flawlessly when they were fitted to the motorcycle. I changed them out just as a precaution against future problems, as I understood they were not the most reliable.
At this point I'm puzzled that the secondary windings' resistance could be nil, yet the coils worked well in service. Can someone offers some insights?
As to the miss, I've changed out the fuel filter as a cheap precaution and will continue to ride the bike in the off chance the poor running can be put down to fueling as opposed to ignition.

    

20Back to top Go down    Re: 1984-85 K100 ignition coils on Fri 3 Apr 2015 - 0:18

japuentes

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Hi there, I've experienced intermittent ignition failures due to a broken wire connection to the coils.
Best regards
JAP


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1988 K100RS SE/ABS
    

21Back to top Go down    Re: 1984-85 K100 ignition coils on Fri 3 Apr 2015 - 5:32

charlie99

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brickrider wrote:I took the suggestion of JAP (post #15 of this thread) and bought new coils to replace the original old style fitted to my 1985 K100RS. During a recent tour of some 2000 miles there were times when the engine seemed to be firing on two cylinders momentarily. I believe it was an electrical issue, as there was at least one gallon of fuel in the tank at those times of poor running, and the fuel pump and filter are quite new. On the tour I changed out the spark plugs for another set of NGK non-resister types, but the intermittent miss recurred. Back home, I measured the secondary ignition wires and the resistance in the coils. Nothing out of spec there. I examined the electrical connections to the pump, both inside the tank and at the under tank connector block. Nothing suspect there. I then measured the original coils and discovered that there is no measureable resistance in the secondaries however, the primary resistance is very close to spec. Those coils preformed flawlessly when they were fitted to the motorcycle. I changed them out just as a precaution against future problems, as I understood they were not the most reliable.
At this point I'm puzzled that the secondary windings' resistance could be nil, yet the coils worked well in service. Can someone offers some insights?
As to the miss, I've changed out the fuel filter as a cheap precaution and will continue to ride the bike in the off chance the poor running can be put down to fueling as opposed to ignition.

have bought coils like that also brick

and they actually work

the voltage will still jump the gap that is internal to the coil secondaries

could jap be onto it ?

a slightly high resistance connector- leadat the coil primary might be a reason ...road conditions may affect that connection periodically ?


maybe a test of the breather system to the tank could prove worthwhile also ...no need to have a high vacuum inside there as the fuel load decreases


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

22Back to top Go down    Re: 1984-85 K100 ignition coils on Fri 3 Apr 2015 - 12:17

brickrider

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Thanks for your thoughts guys.
Charlie, I understood JAP's comments to refer to the 12v. wire that feeds the coils having a short. Perhaps I've misunderstood....
You say you've also bought the same coils I am now using and they work, but seem to discount that in your following comments Exclamation
I'd thought about vacuum in the fuel tank, as that has been an issue in the past with bike with carburettors, but I guess I dismissed it because the Ks have FI. Do you think that could still be an issue? In any case, when I changed the fuel filter I had a good look at the vent hole under the cap and all looked to be in order.
I'm unable to ride the bike at this time, but I hope (ever optimistic!) that cleaning various connectors and changing the filter will have resolved the issue. Once I regain my health I shall try to prove that.

    

23Back to top Go down    Re: 1984-85 K100 ignition coils on Fri 3 Apr 2015 - 13:09

charlie99

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meant that I had bought the old black type coils ....that measured open circuit ...but actually sparked well ....currently not using them (they were for spares, but I got stung by an invisible supplier )

not just the vent that catches water around the lid ....there is usually a pipe that travels from the filter basket up to another metal tube which exits the tank at the back .= vent ( depends on year model though ? after85 )

no was meaning that if the wires that go to the coils had become frayed ...less copper conductormaking the connection or those spade terminals corroded ...would let less current get to and from the coils ....making for an intermittent - erm low spark energy out the secondarys

hope that helps


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

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