globalrider
Alps Adventurer
This isn't news since I've read about it shortly after buying my 1990 R100 GS new back then.
But I thought I'd post some info, numbers and photos in case there are any other airhead riders still riding with their original "grey" ignition coil, as I have for the past 25 years.
For some time now, I noticed a slight hesitation at idle and off idle into the lower RPM range. At higher cruise RPM, my GS seemed normal and even pulled well.
I suspected slightly dirty idle jets, so I inspected them; they were fine and still bright and shiny from the last time I had them out many years ago. By the way, I polish my brass jets and associated parts and have found that they stay clean for years.
The next possibility that crossed my mind was a faulty electrical connection and I remember my GS shutting down while on a ride. Roadside removal of the gas tank and moving the main (red, black and white) connectors on the bracket on the right side of the frame tube had me running again in minutes. When I got home, I used a long thin awl used for metal layout to expand the bullet shaped connectors for a better fit. That was over 20 year ago and the connectors were still tight and shiny today. That wasn't the issue.
By the way, also check that all the connectors in the ignition module connector housing are snapped into place. Shortly after taking delivery of my new GS, I also noted an ignition hesitation. It ended up being a connector pin not fully seated (not snapped in) into the housing...and sure enough, it was the kill switch wire. Solved that one as well.
Then, looking at the ignition coil, I spotted a thin line that could have been a mold flashing...or a crack. Unfortunately, the latter.
BMW 12-13-1-243-910 / Bosch 0 221 500 200
Original "Grey" Coil Measurements
Primary winding: 1.21 ohms (in spec for the original "grey" coil).
Secondary winding: open circuit. Later when I had the coil removed, tapping the coil gave me measurements of 8.95K ohms and open circuit.
BMW 12-13-1-244-426 / Bosch 0 221 500 203 Ignition Coil
New Coil Measurements:
Primary winding: 0.50 ohms (in spec...for the new style coil)
Secondary winding: 12.91K ohms.
I was concerned with the reduction in primary resistance between the old and new style ignition coils; roughly doubling the current that the ignition module needed to deal with.
So I ordered a new "Heavy Duty" Ignition Module Control Unit with integrated Heat Sink. I would want to see the electrical specifications for the old and new style ignition module control units before believing in any Heavy Duty claims.
The "early style" ignition module control unit was bolted to a separate heat sink, hopefully with a good coat of heat sink compound between the two parts which I would renew from time to time.
The new "Heavy Duty" Ignition Module Control Unit with integrated Heat Sink requires a bracket from BMW that bolts in the same place the old style heat sink did.
The new ignition coil and ignition module control unit installed. By the way, I used heat sink compound between the bracket and integrated heat sink.
Full line of photos here.
My GS runs well again.
But I thought I'd post some info, numbers and photos in case there are any other airhead riders still riding with their original "grey" ignition coil, as I have for the past 25 years.
For some time now, I noticed a slight hesitation at idle and off idle into the lower RPM range. At higher cruise RPM, my GS seemed normal and even pulled well.
I suspected slightly dirty idle jets, so I inspected them; they were fine and still bright and shiny from the last time I had them out many years ago. By the way, I polish my brass jets and associated parts and have found that they stay clean for years.
The next possibility that crossed my mind was a faulty electrical connection and I remember my GS shutting down while on a ride. Roadside removal of the gas tank and moving the main (red, black and white) connectors on the bracket on the right side of the frame tube had me running again in minutes. When I got home, I used a long thin awl used for metal layout to expand the bullet shaped connectors for a better fit. That was over 20 year ago and the connectors were still tight and shiny today. That wasn't the issue.
By the way, also check that all the connectors in the ignition module connector housing are snapped into place. Shortly after taking delivery of my new GS, I also noted an ignition hesitation. It ended up being a connector pin not fully seated (not snapped in) into the housing...and sure enough, it was the kill switch wire. Solved that one as well.
Then, looking at the ignition coil, I spotted a thin line that could have been a mold flashing...or a crack. Unfortunately, the latter.
BMW 12-13-1-243-910 / Bosch 0 221 500 200
Original "Grey" Coil Measurements
Primary winding: 1.21 ohms (in spec for the original "grey" coil).
Secondary winding: open circuit. Later when I had the coil removed, tapping the coil gave me measurements of 8.95K ohms and open circuit.
BMW 12-13-1-244-426 / Bosch 0 221 500 203 Ignition Coil
New Coil Measurements:
Primary winding: 0.50 ohms (in spec...for the new style coil)
Secondary winding: 12.91K ohms.
I was concerned with the reduction in primary resistance between the old and new style ignition coils; roughly doubling the current that the ignition module needed to deal with.
So I ordered a new "Heavy Duty" Ignition Module Control Unit with integrated Heat Sink. I would want to see the electrical specifications for the old and new style ignition module control units before believing in any Heavy Duty claims.
The "early style" ignition module control unit was bolted to a separate heat sink, hopefully with a good coat of heat sink compound between the two parts which I would renew from time to time.
The new "Heavy Duty" Ignition Module Control Unit with integrated Heat Sink requires a bracket from BMW that bolts in the same place the old style heat sink did.
The new ignition coil and ignition module control unit installed. By the way, I used heat sink compound between the bracket and integrated heat sink.
Full line of photos here.
My GS runs well again.
