The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: tunnelrider on July 06, 2017, 01:44:41 AM
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Hi everyone, in my southern mid winter madness of intending to just replace the timing chain I'm getting further and further away from completing the task.. While splashing the more exposed than normal bike frame with some paint, the latest tangent involves a Dyna Coil, a severely corroded HT plug and a cracked-right-through coil bracket.
The coil was still held up by one half of the bracket. The rear HT lead socket in the coil is shiny and perfect, the front one has the corrosion and is also the side of the bracket that was cracked and not held to ground properly. Would anyone be able to inform me if the corrosion would be from the cracked bracket or maybe water finding it's way into the front socket? Both HT leads have been well sealed by rubber boots, however, perhaps it is possible the '94 Dynacoil has been letting in rain etc around the centre shaft and making it's way to the front socket? Looking at the HT plug it's amazing it still was firing OK!
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I very much doubt the bracket has anything to do with corrosion in the HT connection.
Other than as a temporary measure don't be temped to mount the coil with tie wraps. Any coil that that has the laminated core exposed at either end is designed to have both ends connected to a metal mounting bracket in order to complete the magnetic circuit of the core. It's not that it won't work if you don't, but it will be less efficient because leaving the core ends open circuit changes the inductance value of the coil.
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Hi Barry, thanks for your reply. Unfortunately my first picture has some green masking tape covering the front end of the bracket that was attached to the front end of the laminated core. This would have had no ground with the cracked bracket but the other end of the coil was still grounded ok. Anyway, unlikely to have caused the corrosion. Yes this will be repaired and coil grounded properly before using the bike again, still got a number of jobs left to do. Other than looking at the quality of the spark, does anyone know of a test that may indicate the health of a coil?
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Testing coils under the voltage stress of operation is not easily done other than as you say by observing the colour and strength of spark.
You can measure the primary resistance which for a green Dyna coil (if that's what it is) should be a nominal 3 ohms. Not sure what the secondary winding resistance should be but it will be in the order of 10k -15k ohm. Maybe the Dyna web site will give a specific figure.
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It appears that the metal that was used to fabricate the adapter plate for the coil, was too thin .
It cracked right at the edge of the plate on the frame that the adapter plate mounts .
My best guess, is that the rubber boot over the ignition lead at the coil, didn't seal very well and water got trapped in there .
Not a bad idea, to coat the boots and lead with dielectric grease before installing them on the coil .
You also reside in a salt water coastal city, ' salt air ' is not kind to motor vehicles .
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After 23 years you were due for a new coil and wires
Definitely nothing here prematurely failed ;D
I have seen this many times
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Definitely nothing here prematurely failed ;D
Thanks for your thoughts all, the bracket was aluminium so it gave a good service 20+ years with the coil you're right, with all the vibration it must've been through. Think I'll replace it with a stainless steel piece I've got lying around. Any tips on refreshing a dull corrosion coil socket or is the coil probably past it now? After 23 years you were due for a new coil and wires
ha ha Mrclub bike you've seen it before thanks for your tips, new coil you reckon. I've read before you can get cheap coils that will do the job from auto wreckers. Test the spark from this one first, got a few things to put back together.
Cheers Barry for the rough resistance guides and Bob, yeah had decided on adding the silicon grease too.
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A small round metal brush will work .
A firearm cleaning brush would do the job, but I doubt you have any gunshops available to you in AU .
A small diameter wood dowl split a little bit at one end, then put a small piece of scotch brite type material in the split .
Put the dowl in a drill motor and see how it works .
Found this chart online .
The green coil, is DC3-1 .
http://www.dynatekuk.com/sport_bikes_ignition_coils.html
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To clean the coil tower fill it with muriatic acid, leave for 10 minutes and rinse. Jenolite for a kiwi.
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Good tips thanks Bob and Motu. I can get analytical grade HCl acid at work so will use that then try cleaning the result with something like you described Bob. We do actually have gun shops here in NZ, hunting and duck shooting are popular with outdoor hardy types, plenty of forest and hills to climb here.
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Very glad to hear that your politicians haven't disarmed you yet!
On Bob's suggestion - you can also use a strip of sandpaper (320 grit maybe) in the slotted dowel.
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Very glad to hear that your politicians haven't disarmed you yet!
Ha no not yet Justin but the nanny state is always bubbling under the surface ready to change things for 'the better of the people'. We do have fairly tight gun laws which means there aren't a huge number of guns floating around to become a toy, which I'm happy about.
Jenolite seems to be phosphoric acid based rather than hydrochloric (muriatic) acid. Most rust stoppers are also phosphoric acid based, while hydrochloric acid is used for pickling steel, which means it is probably stronger. Commercially it's probably cheaper to use phosphoric acid rather than hydrochloric. Might try phosphoric acid first.
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If you're not pressed for time to get this done, vinegar will work, but takes a few days to a week .
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Jenolite seems to be phosphoric acid based rather than hydrochloric (muriatic) acid.
I'm actually using mag wheel cleaner at the moment, I don't know what it is, but it behaves just like Jenolite, so use it as such. Any sort of light acid will do the trick, if it's stronger then shorter pickle time. I wouldn't put any twirlly thing in there, you don't want to remove any metal, or worse. If pickling won't get the gunge out, it's so bad I'd toss it.
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I'm actually using mag wheel cleaner at the moment, I don't know what it is, but it behaves just like Jenolite, so use it as such.
Ha ha you're not wrong Motu, +1 for the mag wheel cleaner suggestion, whakawhetai koe.
I had some in the garage from when I tried using it to clean up the cylinder cooling fins (pretty tiresome job and relatively ineffective). I'd also suspected the coil sockets are aluminium. I pickled the coil socket in 18% HCl acid overnight first and now, after a number of cotton buds buffing the alum cleaner, the socket seems to have a sheen worthy of a decent spark. Still not in a position yet to try it out with a sparking test though, will be another week perhaps.
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Aluminium?
I have never owned a Dyna coil, but for some reason I thought that they would be of a higher standard, with copper in there.
I am disappointed.
I am very anal when it comes to electrical connectors. I love copper, and dielectric (or any kind) of grease.
But, I suppose aluminium must be O.K., considering the path the ground takes from the battery to the starter. :o
I can't say for sure, but I think my Bosch Blues had copper sleeves. Definitely use the copper, solder-on type of butt connector for your plug wires. I have no idea where to buy them. Maybe buy some OEM wires and take them off them?
You are, after all, going to use NGK plug caps if you want to ride in the rain.
I reused my butt connectors many times. They are so much better than then clamp-on butts with the little pointy thing that goes down and hopefully makes contact with the wire.
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You cans till get the solder on style ends
part #12 12 8 536 120
I have a brand new pair but have not installed them yet
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You cans till get the solder on style ends
part #12 12 8 536 120
I have a brand new pair but have not installed them yet
:D
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Hi all, I'm still investigating this oft brought up, probably boring for most topic of coils, since it's off the bike and while reading a lot of info on Snowbum's site (boy he's an electronic whiz), I came across this about green Dyna coil;
"Dyna sells many different coils. Do not use the Green dual-tower 6 volt coil with the Bosch electronic ignitions that came on the BMW Airheads from 1981. Those Dyna coils are 3 ohms, and are marginal in that application."
As my (1994 Dyna) coil is green, 3ohms, how can you tell if it's 6V? Or is 6V because of two towers off one coil? I thought Dyna wouldn't sell 6V coils these days but may be wrong.
Anyhow it has obviously propelled her along for a good amount of time but thinking I might get a more even spark from a new one with lower primary resistance, more matched for the electronic ignition (if the black box can handle it!)
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Tunnelrider,
Go to a car junk yard and find a dual output coil from a petrol car. Choose if possible a Fiat one (as they use Marelli parts with similar specs as the Bosch on our bikes). But of course other makes will do just fine.
Check the primary resistance just to be sure and use it. It will cost you dimes and will work "of the box"... as these are also devised for powerful electronic ignition.
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....."Dyna sells many different coils. Do not use the Green dual-tower 6 volt coil with the Bosch electronic ignitions that came on the BMW Airheads from 1981. Those Dyna coils are 3 ohms, and are marginal in that application."
As my (1994 Dyna) coil is green, 3ohms, how can you tell if it's 6V? Or is 6V because of two towers off one coil? I thought Dyna wouldn't sell 6V coils these days but may be wrong.
Snowbums reference to a Dyna green being 6 V sounds like a mistake to me so I wouldn't worry about running it on 12 V.
By marginal I guess he means with a 3 ohm coil you just have the spark energy of points ignitions instead of the greater energy provided by a 1.5 ohm coil normally used with electronic ignition. That's the theory but if the 3 ohm coil works well when everything is cleaned up you may not see any practical improvement with the correct coil.
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Voltage isn't important it all works on the resistance of the primary winding. 3ohms would work well on a 6V system.
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I agree that ignition coils don't really have a measurable parameter called voltage but the applied voltage together with the primary resistance determines what current will flow. To that extent a coil intended for 6 voltage operation would work great on 12 volts as the primary current would nominally be doubled and spark energy being proportional to the square of the primary current would increase 4 fold. All provided the coil didn't overheat from more current than it was designed for.
Conversely if you used a 3 ohm coil intended for 12 volt operation on a 6 volt system the spark energy would be reduced 4 fold.
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Yes, but bear in mind that the ICU has a limit on the current it can supply.
If the resistance of the coil is too low, the output circuitry of the ICU could fry.... So it is important not to deviate from the value of the OEM coil.
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Thanks to all of you who've replied, I will probably go to the wreckers and find a suitable coil as a comparison. The ICU on my bike seems to be an aftermarket one with the only discernible info "M055" and "P5028" so I'll assume that's good for transistorised ignition and find a coil of approx 1.5ohms, as the OEM was for '81 on.
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Like everyone has mentioned stay with 1.5 ohms and higher and you should be OK
I have used all 3 different Dyna coils 3 1.5 and 0.7 and currently using the green 3 Ohm and it runs just as good as the others
I am using the geeen because the delco ignition module doesn't shut off if the engine is not running with the key still on
so it doesn't over heat
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To that extent a coil intended for 6 voltage operation would work great on 12 volts as the primary current would nominally be doubled
I tried a lower resistance coil on my '71 240Z years back thinking the same thing and got about 30 miles and it died. Some side-of-the-road troubleshooting made me suspect the points breaker arm got so hot it bent and the gap closed up. I eye-ball gapped the points, got to where I was going, and had to do the same drill on the way home - very irritating! I put the original coil back in and all was right with the world...
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I have used an ignition coil from a Mitsubishi Lancer. Just take a look at any wasted spark coils on cars, pick which ever configuration suits. And check the ohms to see if it will work.
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Thanks to all for your really helpful replies and Mrclubike on having used the different primary resistance Dyna coils and have found the green to be no different as far as how well it works. Considering this info, and Barry also said it's unlikely to make much difference, if the spark test works out ok for my cleaned up green Dyna I'll probably stick with it.
It's gonna take me another couple of weeks to get to the stage of being able to do a spark test but at least now the front cover's back on after the timing chain job, I've repainted a number of parts, put a donor engine's cylinders and pistons on (with new rings of course) and got a loose valve guide fixed. Other tasks await finishing like bending a coil bracket, headlight rebuild, new front brake hose, clutch cable, neutral switch and gear shift seal. Who would've thought a snapped timing chain would lead to all of this? ;D