The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: ukzknos on February 17, 2010, 04:55:10 PM
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I recall once reading, but can't now find the thread, about replacement coils for the Bosch 6V 1.2 Ohm.
Can someone tell me what they are?
Thanks
Steve
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Early aircooled Volkswagens used 6V coils. Not sure if they are 1.2 Ohms though. Eurocarparts or GSF should stock them in the UK.
Heres another source. Again the primary impeadance is not specified.
http://www.autoelectricsupplies.co.uk/product/749
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I am using a dual output second hand BMW K100 coil on my 1979 R65 - it runs with a points ignition. This was supplied and suggested by Motorworks - BMW parts suppliers. Works a treat.
This was after the 'bosch blues' kept breaking the frame mounts. They are too heavy really.
Steve Hawkins
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Do you want to keep with (2) 6V coils in series, or are you interested in going to (smaller) dual output coil? I believe that VW 6V coils could work as direct replacement. If you want to go to a smaller, more compact design with dual output, in the USofA, the Dyna "Green" coil is the one you'd get for running with points and the Dyna "Brown" (Really it is orange) is the one you'd get for running with hall effect/electronic ICU.
The Dyna coils have a good track record for reliability and many of us in the states get them from Rick at Motorrad-elektrik:
http://www.motoelekt.com/ignition.htm
He also sells Bosch coils too at the link above.
There are probably sources for these items closer to you if you prefer not to have them shipped from US.
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Barry
http://www.autoelectricsupplies.co.uk/product/749
These are a good price. Do you think they are a 'drop in' replacement or do I need to ensure that the resistance is the same as the standard R65 coils?
Thanks
Steve
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I'm not sure if they are the same or not - I did a quick google search and found this cross reference info based on the coil number I could see on that image:
http://www.currentcare.co.uk/index.php?showprod=7320715
Check the Bosch numbers from your coil(s) against this cross list..
You would need to have a pretty good ohm meter to accurately measure the primary resistance to be 100% sure without any published info on that coil, but the odds are it would probably work with the usual 6V series wiring application.
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Interesting, and even more so the place you found 'current care' is only 3 mile from my home! :)
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I just took a spin around the block. It killed as I pulled into the driveway. took my helmet off and a sizzle and a puff of smoke came from under the tank, still had the key on. so I turned it off and the smoke quit. took off the tank and the coil seems to be the only thing it could have been. definitely no spark now. I was looking forward for this little break after doing taxes all morning. :'(
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Do you think they are a 'drop in' replacement or do I need to ensure that the resistance is the same as the standard R65 coils?
The general rule for points ignitions is that any coil with similar or higher resistance than the standard is ok. Standard coils are 1.2 to 1.5 ohms depending who you believe. Lower than standard resistance will work but the higher current will burn the points quicker and may overheat if you leave the ignition switched on without starting the bike. Electronic ignitions are able to switch higher currents and guard against overheating by turning off the coil after 5 secs if the engine isn't running.
From what I can tell one of the Bosch numbers is the standard black coil and the other is the more powerful blue coil so you should be ok. The only other issue is will the diameter fit your mounting brackets.
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Check out http://www.omegaignitions.com/faq.html for compatable coils. Basically if you have the ignition module (newer - electronic ignition) you can run coils with a lower primary resistance ~ 1.2 ohms total. With the older points only ignition you need the higher ohm coils ~ 2.4 ohms (or two 6v 1.2 ohm coils in series)
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If you want to go to a smaller, more compact design with dual output, in the USofA, the Dyna "Green" coil is the one you'd get for running with points
Does anyone have a wiring diagram for upgrading to the Dyna coil?
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I don't, but it should be fairly simple - just a (2) wires to connect the primary side and (2) connections for the spark plug leads. If you email or call Rick @ Motorrad elektric website link I provided he can give you any help/info you need on how to connect it to your points wires and suggestion on how to mount it.
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To fit a dual output coil just connect the green/blue wire to one terminal and the two blacks to the other. The black/yellow link wire can be discarded. If your new coil has any +ve and -ve polarity markings the green/blue wire should go to +ve terminal.(http://)
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Thats what I did with my cheap K100 dual output coil.
Nobody, it seems, is as cheap as I am!
Steve H
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Steve
How much lighter was the dual output coil compared to the heavy originals ?
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Thats what I did with my cheap K100 dual output coil.
Nobody, it seems, is as cheap as I am!
Steve
If you were really cheap you would have gone for the coil off a China cloned CB250 not a K100! ;D
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It was close to the weight of one of the bosch blue coils. You cannot use the original mounts, but mine had broken anyway, both on the frame and I had already replaced the clamps more than once.
A little bit of cutting and bashing on the coil had the new coil mounted underneath the 'relay tray' underneath the front of the tank on the right hande side. Near where your front coil is currently mounted.
Half an hour with a hacksaw and a drill. Been there for a few years now. 1979 R65 with point ignition.
I get the impression people don't believe me....Or would prefer to spend lots of $/£ unnecessarily. Contentious, I know.
Steve H
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Fitted a Dyna coil DC1-1 (green 3 Ohm) today and I have to say the engine started really easily when compared with what it was like previously.
Also when I turned the engine over with a plug earthed to the side of the cylinder the spark was noticeably stronger.
Hopefully this will be a good investment to replace the original 30 year old coils!
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+1 on the Dyna Coil. JUst replace the two Bosch with the one Dyna.
15 wire to one side and the 1 wire to the other with no connecter wire between. Simple.
I like Rick at Motoelectric because he has a monting bracket to go with the new coil. I mounted on the back coil bracket on my 1980 as the front one is broken.
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I mounted on the back coil bracket on my 1980 as the front one is broken.
I mounted mine on the back coil mount too as the front one broke when I was de-mounting the coil! (also 1980) spooky!!
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Its a weak spot! Many of the 79 - 80 bikes have this problem. When it first broke, I chopped off a CocaCola plastic bottle pushed it over the front coil to keep the thing fron grounding out my wriing connectors, and tye wrapped it to the relay tray. I did my 2006 50 hours coast to coast with this set up. 7500 miles in three weeks in Sept 2006 with no problems.
Crazy!
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My front coil was mounted to the main frame tube with zip-ties for decades.
I just switched to over-side hose clamps a few years ago.
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My front coil was mounted to the main frame tube with zip-ties for decades.
I just switched to over-side hose clamps a few years ago.
Way ghetto, Rob. I love it. Monte