Is there a way to bench test a suspect Lucas coil?
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Just been through this too. I switched plug wire ends at the coils & the miss went to the other side. I borrowed a used set of coils (thanks Jerry) and it ran fine. I thought it was a bad lead to my ancient Boyer trigger contacts but they are ok. As for testing a coil from what I have learned ( but could be wrong, no expert here) you can use a basic Ohm meter & check to see if it's "leaking" or shorting by going from the body to any & all leads & the center where the plug wire goes. If you get any reading at any point the coil is shorting. I have decided it's time to move on from my duel 6 volt coils wired in series and go to a single duel output one from CNW, this led me to decide to order a Tri Spark EI because for ease of mounting the coil the Boyer brain box had to move. And after looking at the timing plate again I realized the trigger coils themselves were falling apart!! The Boyer served flawlessly for a very long time but it's getting to old and crispy. Hope the word "crispy" doesn't describe what the Tri-Spark's parts mounted in the timing cover become but I'm willing to give them a try. PS, don't need to rekindle that debate.
o0norton0o
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I've also switched from the original 12 volt coils to two 6 volt coils in series, and then to a single harley dual lead coil
As I recall, when I was having ignition issues (which turned out to be a spark plug that wouldn't fire under compression in the engine, but would fire when held against the head) I wrapped my coils in clear plastic tape and remounted them in the bracket to try and eliminate a crushed coil as the cause of my ignition miss.
Because my ignition miss was a bad spark plug, I have no way of knowing if insulating the case of the coils from grounding out to the frame by using tape as an insulator will allow a crushed coil to function properly. It seems logical that it should, so you could tape your coils and remount them and see if that eliminates the miss.
*The spark plug that sparked ok outside of compression, but did not fire in the bike took numerous days to find since I thought it tested as "good". Needless to say, intermittent problems are the hardest to track down because you never know if the bad part is just temporarliy working again, or if you've finally replaced the intermittently bad part...
As I recall, when I was having ignition issues (which turned out to be a spark plug that wouldn't fire under compression in the engine, but would fire when held against the head) I wrapped my coils in clear plastic tape and remounted them in the bracket to try and eliminate a crushed coil as the cause of my ignition miss.
Because my ignition miss was a bad spark plug, I have no way of knowing if insulating the case of the coils from grounding out to the frame by using tape as an insulator will allow a crushed coil to function properly. It seems logical that it should, so you could tape your coils and remount them and see if that eliminates the miss.
*The spark plug that sparked ok outside of compression, but did not fire in the bike took numerous days to find since I thought it tested as "good". Needless to say, intermittent problems are the hardest to track down because you never know if the bad part is just temporarliy working again, or if you've finally replaced the intermittently bad part...
jimbo said:
This http://www.ebay.com/itm/Lisle-Coil-On-P ... 1443743024 looks interesting and simple enough. Watch out for shipping costs! There must be more products that work like that one, I'm sure a little search on e-Bay or the interweb will find it.
Jean
Wrapping a damaged coil in tape to stop it from grounding to the frame will do nothing to fix it. If the internal coils are touching the body they will no longer function properly or at all. Again, use a ohm meter. Put one lead to the body and touch the other lead to the + , the - or the center hole. One at a time. If you get a reading then you have a coil that is damaged. This MAY only show up when it's clamped & even then it could be intermittent. With 6 volt coils using the ohm meter put the leads on both the + & - and it should read around 1.9 ohms.
An ohm or multimeter can tell you if you have a short or an open circuit, but if it is that easy you would probably know anyway.
Shops used to have a big lump of kit for testing magnetos and distributors/coils. They had an adjustable spark gap so you could put the item under pressure.
I have an inkling there was a version which had a spark plug firing in to a pressure chamber with a window, for a slightly more realistic test.
Maybe an old thymey place near you has one?
The first type could be approximated using an old distributor in a lathe or milling machine. An even cruder version could use a points baseplate and an electric drill to open the points.
Shops used to have a big lump of kit for testing magnetos and distributors/coils. They had an adjustable spark gap so you could put the item under pressure.
I have an inkling there was a version which had a spark plug firing in to a pressure chamber with a window, for a slightly more realistic test.
Maybe an old thymey place near you has one?
The first type could be approximated using an old distributor in a lathe or milling machine. An even cruder version could use a points baseplate and an electric drill to open the points.
A
Anonymous
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From Chilton's 1973 manual.
Ta.
Ta.
Short answer, No. Not unless you have an old style speed shop nearby.
When the coil gets hot it shorts out. Until it gets hot, it is fine. I have found that coils that are breaking down have different resistances than shown in Needing's post and one will be different than the other.
If you are feeling adventurous, securely tape a spare coil to the frame down tube. Ride the bike until the 'bad' coil acts up. Switch the leads to the 'good' spare coil and see if the problem is solved.
If the coil has been squashed by the clamp, it is suspect, but I have had them go for quite a ways.
Greg
When the coil gets hot it shorts out. Until it gets hot, it is fine. I have found that coils that are breaking down have different resistances than shown in Needing's post and one will be different than the other.
If you are feeling adventurous, securely tape a spare coil to the frame down tube. Ride the bike until the 'bad' coil acts up. Switch the leads to the 'good' spare coil and see if the problem is solved.
If the coil has been squashed by the clamp, it is suspect, but I have had them go for quite a ways.
Greg
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NOTE: I have twice had factory type coil short to case whiule away from home and got back home fine after hair pulling diagnosis then using clear packing tape from a business to insulate and to hold to frame outside of normal crushing mount. I put small washers between the clamp to avoid crushing when tight enough to stay put.
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The Factory Workshop Manuel for a Norton Commando explains how you can bench test a spark coil. Here is a picture of the page that describes this:
This is a picture of the same basic setup as described in a BSA Service Manual. This diagram gives you a better idea of how to make the "ionizing electrode". You would adjust the gap to 8 mm for a 6 volt coil and 9 mm for a 12 volt coil:
I hope this is of some help,
Peter Joe
This is a picture of the same basic setup as described in a BSA Service Manual. This diagram gives you a better idea of how to make the "ionizing electrode". You would adjust the gap to 8 mm for a 6 volt coil and 9 mm for a 12 volt coil:
I hope this is of some help,
Peter Joe
jimbo
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