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#241976 - 03/09/09 4:51 pm testing Lucas coils?  
Joined: Aug 2007
Posts: 1,038
snowbeard Offline
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snowbeard  Offline
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US citizen in Lisbon, Portugal
so can anyone tell me what readings I should get to know if the coils are good? I'd need to be told which connection to which and what the resistance should be?

also, just so you know how little I know, what is the rubber covered box between the two that is connected to both? blush

the bike is a mess, wires cut at the headlight and what is left on the frame have been spliced and are the wrong colors, as well as mostly disconnected.

I just want to see if I can get the engine to fire up, I don't plan to do the whole thing until I see that.

thank you all once again!!


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
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#242007 - 03/09/09 6:41 pm Re: testing Lucas coils? [Re: snowbeard]  
Joined: Sep 2008
Posts: 722
jaycee Online content
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jaycee  Online Content
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Posts: 722
angeles city, rp
why not just hot wire it.( disconnect every thing else) clean points and seeif you have fire?givenyour stated goal i recommend this. refer to any coil ignition schematic,but since you asked if bike is positive ground ,battery hot, negative,goes to neg coil terminals.positive goes to the points. ballast resistor can go in series to each coil either on hot side or points side it makes no difference.if no ballast resistor is present dont worry about it now given your stated goal it doesnt matter,rubber covered box sounds like ignition capacitors,these will be wired to POINTS SIDE OF COIL.this will yield a working system,if you follow these directions it should fire.make sure points are clean,let me know if you get into trouble,regards,john from the soviet socialistic republic of hawaii.

#242056 - 03/09/09 9:56 pm Re: testing Lucas coils? [Re: jaycee]  
Joined: Aug 2007
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snowbeard Offline
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snowbeard  Offline
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US citizen in Lisbon, Portugal
Hey John, I saw a couple of your posts about similiar things in my searches. looks like we're on the same wavelength.

this bike is in such disrepair that I can't even start with a hot wire... so I'm trying to find all the broken parts early so I can source them and have what should be mostly working before I go too far. so far I've cleaned out the frame oil filter, replaced an oil line, checked on the points, and now tested the coils.

I checked resistance on the + to -, as well as the lead to + and lead to - (which I now realize are the same) I have a triumph T150V frame with three coils on it as well, so I checked all five for reference.

on both the A65 coils I got
+to- 3.7 Ohms
lead to +/- 4.82K Ohms

on teh triple I got
+to- on one 5.1 Ohms
other two 3.6 Ohms
lead to +/- 5.0-5.1K Ohms on all three


so I figure all five haven't fried themselves the same way and I can assume that they are all mostly alright?

I still have to get oil, check the rest of the wires, and clean the plugs. I may even be able to try it out this evening if I play my cards right... probably not tho.

thanks so far!!

Last edited by snowbeard; 03/09/09 10:00 pm.

=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#242061 - 03/09/09 10:11 pm Re: testing Lucas coils? [Re: snowbeard]  
Joined: Jun 2002
Posts: 9,297
Stuart Online content
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Stuart  Online Content
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Scotland
Hi,

Originally Posted By: snowbeard
readings I should get to know if the coils are good?

Lucas 12V coils (17M12) - 4 to 4.5 Ohms between the low-tension terminals.

Lucas 6V coils (17M6) - 1.5 to 2.2 Ohms between the low-tension terminals.

Either coil type - 4 KOhms between either l-t terminal and the h-t terminal, infinte Ohms between any terminal and the case.

If you want to know values for 4V coils or PVL coils, shout.

Originally Posted By: snowbeard
rubber covered box between the two that is connected to both?

Two male tab (or three on a triple) terminals sticking through the side opposite the mounting? If so, sounds like the condensors.

Hth.

Regards,

#242072 - 03/09/09 11:06 pm Re: testing Lucas coils? [Re: Stuart]  
Joined: Aug 2007
Posts: 1,038
snowbeard Offline
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snowbeard  Offline
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US citizen in Lisbon, Portugal
thanks Stuart, so do you think my measurements show the coils to be "bad" or are they close enough?

oh yes, those would be the condensors. thanks! (I'm a chemist, not a mechanic, I do appreciate the help!)

Last edited by snowbeard; 03/09/09 11:07 pm. Reason: stupidity

=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#242075 - 03/09/09 11:25 pm Re: testing Lucas coils? [Re: snowbeard]  
Joined: Oct 2008
Posts: 4,860
DavidP Offline
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Gnashville
You can test the coils on the bike.
Connect a battery or charger, negative lead to coil, positive lead to engine and coil. Place the plug on the head. Remove the positive connection at the coil, you should see spark at the plug.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#242318 - 03/11/09 10:29 am Re: testing Lucas coils? [Re: snowbeard]  
Joined: Jun 2002
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Stuart Online content
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Stuart  Online Content
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Joined: Jun 2002
Posts: 9,297
Scotland
Hi,

Originally Posted By: snowbeard
so do you think my measurements show the coils to be "bad" or are they close enough?

Firstly, in all cases, I assume we're talking about 12V coils fired by points, not something like a Rita or Boyer-Bransden e.i.?

If so, hmmm ... good question. The ranges I quoted are a combination of those I obtained from Mistral Engineering (Rita suppliers to the gentry) and Bransden Electronics; i.e. each gave me smaller, but slightly different, ranges that they'd consider 'good'. Thus, imho, while yours aren't 'bad', you could probably do 'better' - I wouldn't chuck 'em but I'd bear it in mind and carry a small meter to any swap meet I went to.

Hth.

Regards,

#242386 - 03/11/09 5:50 pm Re: testing Lucas coils? [Re: Stuart]  
Joined: Aug 2007
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snowbeard Offline
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snowbeard  Offline
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US citizen in Lisbon, Portugal
thanks Stuart. so I guess I should back up and give some info.

I have an old A65 thunderbolt, 1971 by the numbers. It is the original points and coils by what I can tell, so I assumed they were 6V, but I know less than nothing about the A65's, I've so far only learned my magneto...

I hope to win a haynes for this in the very near future, but until then I rely on the helpfulness of the forum. Can anyone tell me what OEM voltage the coils were?


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#242581 - 03/12/09 9:04 pm Re: testing Lucas coils? [Re: snowbeard]  
Joined: Oct 2008
Posts: 4,860
DavidP Offline
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DavidP  Offline

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Posts: 4,860
Gnashville
OEM coils were 12V in 1971.
I'm using a Sparx ignition with 6V coils.
I just checked my original coils, 4.1 and 3.9 Ohms across the primary, 5K and 5.1K primary to secondary.

BTW: The seller triumph_norton_bsa on eBay sells repros of the factory manuals and parts books for less than you'll pay for the Haynes book. They come nicely bound with a PDF copy on CD for backup.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#242742 - 03/13/09 4:04 pm Re: testing Lucas coils? [Re: DavidP]  
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snowbeard Offline
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snowbeard  Offline
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Thanks David, I'll have to hook my suzi battery then and see what I can do!!

I think I need the parts book most, I just got a pre-unit haynes with a project I picked up (that post will be up soon!) but I had already bid on both unit and preunit haynes on eBay, so I may end up with tons of manuals all at once!!


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#243425 - 03/16/09 11:22 pm Re: testing Lucas coils? [Re: snowbeard]  
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snowbeard Offline
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snowbeard  Offline
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Posts: 1,038
US citizen in Lisbon, Portugal
well I spent the whole of the weekend under the thunderbolt, she's got a working oil system now, cleaned out a pile of sludge, man someone must have hated this bike! flushed it with PBBlaster thru the oil feed for a couple hundred mL's, then added some older oil to clean that out and I'll change it proper once I think it run thru just a little bit.

thank you very much for the helpful suggestions, especially the step by step there John!! once I sat down and drew that out I was able to hook it all up and get spark on both plugs!!

new wires going on tonite since the spark is kind of weak. I got one good backfire for all my efforts, which was pretty exciting/depressing. I finally won a haynes for it so I'll try to check the timing next, but we'll see what kind of difference the wires make first...

thanks again!!


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#243497 - 03/17/09 9:08 am Re: testing Lucas coils? [Re: snowbeard]  
Joined: Jun 2002
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Stuart Online content
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Stuart  Online Content
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Joined: Jun 2002
Posts: 9,297
Scotland
Hi,

Originally Posted By: snowbeard
I got one good backfire

Can be a symptom of timing on the exhaust stroke. Haven't managed to do it on a twin but easy to do on a triple. whistle

Hth.

Regards,

#243557 - 03/17/09 5:27 pm Re: testing Lucas coils? [Re: Stuart]  
Joined: Aug 2007
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snowbeard Offline
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snowbeard  Offline
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Posts: 1,038
US citizen in Lisbon, Portugal
I suspected the valves not entirely closing or opening, as it seems to cough back out the carb as I kick it thru (covered the intake with a piece of cloth to try to "choke" it a little).

but it has some compression (100+ on one side, ~90 on the other) and holds what it has for at least the minute or so I watched each. I put some rags over the tailpipes as well so I could get a visual on whether there was exhaust pressure. it's sucking down the gasoline as I kick it thru, so I have some hope that things are actually sucking, compressing and exhausting...

well, it's exhausting me at least... ;-) haynes manual en route, so at least I got that going for me.


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid
#243653 - 03/18/09 1:54 am Re: testing Lucas coils? [Re: snowbeard]  
Joined: Dec 2005
Posts: 81
stevehi1 Offline
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stevehi1  Offline
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Dartmouth NOva Scotia
Switch the plug wires at the spark plugs. put the right side on the left and the left side on the right.


1969 A65L
1969 A65TC
2005 FLHTI
2007 Vespa LXV 150
#243701 - 03/18/09 3:16 pm Re: testing Lucas coils? [Re: stevehi1]  
Joined: Nov 2005
Posts: 7,218
JubeePrince Online content
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JubeePrince  Online Content

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Posts: 7,218
Back on the mainland!
You can find some coil values here (for purposes of Boyer):

http://www.tioc.org/boyercoildata.htm

HTH,

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
#244579 - 03/23/09 6:00 pm Re: testing Lucas coils? [Re: JubeePrince]  
Joined: Aug 2007
Posts: 1,038
snowbeard Offline
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snowbeard  Offline
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Joined: Aug 2007
Posts: 1,038
US citizen in Lisbon, Portugal
thanks for the helpful suggestions, tried swapping the plugs too, good thought tho!

I checked again with a new plug wire, the old one was one of those silicon or teflon inner things? black fibers instead of wire, so with a copper core wire I have decent spark on both sides!

still waiting for my manual, but I just won a 928 body and slide on eBay, so I'll get some bits for that and try it with the correctly set up carb instead of some random monoblock.

thanks!!

fingers crossed!!


=================
/1957 BSA A10 Spitfire Scrambler (in a friend's shed)
/1960 BSA Super Rocket Basket Case (in the attic!)
/1987 BMW K100LT nekkid

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