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Discussion Starter · #1 ·
I have a question about the coils on Triumph 500 (ET) but not sure where to post? Advise please.
Many thanks for your reply.
I have fitted after market coils to my 1966 Tiger . Since fitting I've had no end of trouble in getting the bike to run properly!. Even broke a Kickstarter in the process.
With nice new/clean plugs the bike would start almost first time, followed by a brief minute of reasonable running and then it's as if the choke was switched on!. On inspection the plugs were sooty black!.
Not thinking, I assumed that it was running rich and must be something to do with carb/fuel delivery. After trying new jets, needle etc etc, the bike did not run any better!.

So here's the thing, when I test my new aftermarket coil with a multimeter it shows Secondary to be 11.4K!.
I cannot find what the correct rating for my bike should be and my old coils(original) don't give me any reading at all on my meter.
Logic is telling me that if the resistance is more in a coil, then the plug spark will be weaker on an et bike like mine.

If the plug is not burning all the fuel then it will behave like the choke is on??????,..........or am I barking up the wrong tree?.
Simply put, does my new coil have too much resistance causing the plug to have less spark and eventually sooting up?.
I have a question about the coils on Triumph 500 (ET) but not sure where to post? Advise please.
 

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Hi,
fitted after market coils
Since fitting I've had no end of trouble in getting the bike to run properly!
Mmmm ... several things in your post make me suspicious:-

With nice new/clean plugs the bike would start almost first time, followed by a brief minute of reasonable running and then it's as if the choke was switched on!
What carburettor? If it's an Amal, are you actually using the 'choke'? Reason I ask is if you aren't familiar with Amals, the 'choke' works the opposite way to most (all?) other carbs., particularly if it's cable operated - Amal, slack wire is 'choke on', tight wire is 'choke off'. If the bike has an air cleaner fitted, remove it and check the 'choke' (more correctly "air slide") is actually rising when any choke cable's tightened or lever's operated.

when I test my new aftermarket coil with a multimeter it shows Secondary to be 11.4K!.
If your T100 has ET ignition, it cannot use one coil (singular, with two HT leads?). Like any alternator, the special ET one generates AC (Alternating Current); however unlike other alternators, the AC is not rectified, so the coils (2) must be both separate for each cylinder and special AC ones.

Aside, if you have a single DC coil with two HT leads and you are measuring between HT and LT, yes it will appear high-resistance; unlike ignition coils with a single HT lead, there isn't any physical connection between HT and LT.

cannot find what the correct rating for my bike should be and my old coils(original) don't give me any reading at all on my meter.
If you bike's ignition really is ET (alternator stator has five wires), some modern dirt bikes use AC coils; ET confirmed, I'll look up the sources I know for suitable modern coils.

"Picture's worth a thousand words" etc., could you take and post photos. of your bike, the original coils and the coil(s) you're trying to use now?

Just as a matter of interest, is/are your bike's engine and frame number/s between H40528 and H40868?

Regards,
 

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Discussion Starter · #3 ·
Hi,

Mmmm ... several things in your post make me suspicious:-


What carburettor? If it's an Amal, are you actually using the 'choke'? Reason I ask is if you aren't familiar with Amals, the 'choke' works the opposite way to most (all?) other carbs., particularly if it's cable operated - Amal, slack wire is 'choke on', tight wire is 'choke off'. If the bike has an air cleaner fitted, remove it and check the 'choke' (more correctly "air slide") is actually rising when any choke cable's tightened or lever's operated.


If your T100 has ET ignition, it cannot use one coil (singular, with two HT leads?). Like any alternator, the special ET one generates AC (Alternating Current); however unlike other alternators, the AC is not rectified, so the coils (2) must be both separate for each cylinder and special AC ones.

Aside, if you have a single DC coil with two HT leads and you are measuring between HT and LT, yes it will appear high-resistance; unlike ignition coils with a single HT lead, there isn't any physical connection between HT and LT.


If you bike's ignition really is ET (alternator stator has five wires), some modern dirt bikes use AC coils; ET confirmed, I'll look up the sources I know for suitable modern coils.

"Picture's worth a thousand words" etc., could you take and post photos. of your bike, the original coils and the coil(s) you're trying to use now?

Just as a matter of interest, is/are your bike's engine and frame number/s between H40528 and H40868?

Regards,
Yes Stuart, the bike has 5 wires, 2 coils and frame number T100SCH40749.
I will try and attach photos.
By the way, found out the primary resistance should be 2-3 ohms,.......my new coil shows 1.3ohms!.
I still think 11.4K (each coil), seems excessive.
Funny thing is the supplier assures me that plenty of people have had these coils with no problems!.
He suggests I check my stator and magnets. It does make sense but I'd like to suss this coil situation first.
I appreciate your help.
Tire Fuel tank Land vehicle Wheel Vehicle
 

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Yes Stuart, the bike has 5 wires, 2 coils and frame number T100SCH40749.
Hi Furbrain,

I can say fairly confidently that your bike looks like a 1966 T100SC ex South African Army bike. I worked on them during my national service in South Africa, in the Technical Services Corp (equivalent of REME in UK). They indeed had ET ignition and I remember those open ET ignition coils with their translucent encapsulation clearly.

The original ET ignition coils are specifically for a higher voltage AC ignition system and are not the same as the usual 6 Volt coils. If you can't get the correct coils, taking into account the 2-3 Ohms that you say the primary windings on the original coils read, it may be more appropriate to try 12 Volt coils.

With regard to the alternators used on these bikes, what I specifically remember is how many of the 5 wire alternator stators used on those bikes, burnt out their lighting windings. The problem seemed to be that for daytime running, the lighting coils ran unloaded and with the combined effects of vibration on the open (non encapsulated) windings on those earlier stators and high open-circuit voltages, the coil insulation broke down, the windings short circuited and failed. In fact, most of the work I did on those bikes was replacing failed stators.

Even when working correctly, the 6 volt lighting system doesn't have a lot going for it either and can only power a fairly low wattage (6V 25/25W ?) headlight bulb. The original headlight on those bikes was 5" in diameter and took a BPF bulb. I can't be sure looking at the photo, but it looks likes yours may have been changed to a 7" unit.

If you still have an original (un-encapsulated) original 5-wire alternator, the best suggestion I can think of, is to bite the bullet, cut your losses and change the electrics to 12 Volts, by fitting a standard RM21 alternator stator and rotor. You will need a regulator rectifier, but if you don't want to fit a battery, you should be able to use a large capacitor (4700 micro Farad 25 Volts) instead of a battery, if you still have the points and condensers. You will of course need 12 Volts ignition coils and light bulbs.

As a side-note, I seem to remember that the Auto Advance Unit on those bikes had a quite limited advance (5 camshaft degrees seems to spring to mind) compared to the regular 12 Volt bikes with their 12 degrees. That should still be okay if its working - I remember them sticking and failing to advance quite often, unless the shaft inside the points cams was regularly oiled.

The choke on the monobloc carb was a spring return arrangement directly on the carb top, that was pulled down to put the choke "on". I don't remember it ever being needed. Tickling the carb was normally all that was needed to get it going.

Terry
 

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Yes Stuart, the bike has 5 wires, 2 coils and frame number T100SCH40749.
Here's a pic' I found on-line of what they looked like when they were supplied to the military out there:

763805


There were some changes between the earlier and later ones supplied. The seat was smooth topped on the earlier ones, while the later ones had the pleated dual seat as this one in the pic' shows. I seem to remember that the tank badges varied between the "Eyebrow" type and the "Garden Gate" type as you seem to have. All had a parcel carrier mounted on top of the petrol tank. In original trim, they were fitted with crash-bars as was a legal requirement for any motorcycle over 250cc back then in SA and they came with pannier mounting frames, supplied by Triumph. The one in the pic seems to be one of the later ones, because it has two cables coming out of the carb' top for the handlebar mounted air lever. They had no ignition switch, but were fitted with a cut-out button, which I see you have mounted on the left handlebar.

Until I was called up to the army, I had only worked on Japanese bikes (Including a period in a Bike shop), but these were the first British bikes that I worked on. I liked them a lot and was rebuked by our Sergeant-Major (workshop foreman, in effect) for spending as much time test riding them as I spent working on them. :)

I was very keen to buy one when the army disposed of them by auction, but they were sold in lots and snapped up by dealers, who then put a big mark-up on them. So I missed out.
 

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Hi,
is/are your bike's engine and frame number/s between H40528 and H40868?
frame number T100SCH40749.
As Terry's posted, one of the batch supplied to the SA army.

There were some changes between the earlier and later ones supplied. The seat was smooth topped on the earlier ones, while the later ones had the pleated dual seat as this one in the pic' shows. I seem to remember that the tank badges varied between the "Eyebrow" type and the "Garden Gate" type
They were built at the beginning of the '66 model year, which was the first year of the 'eyebrow' tank badges and 'pleated' (ribbed) seat covers; I'll guess the "earlier" ones had nominally-'65 tank badges and seat covers, "later" ones had the new-for-'66 bits?

no ignition switch, but were fitted with a cut-out button,
Lucas/Triumph never supplied an ignition switch with ET electrics. ET works like a magneto, which didn't have an ignition switch plus I suspect the army hardly wanted ignition keys to keep track of and would immobilise a bike possibly miles from anywhere if lost by a careless squaddie.

bike has 5 wires, 2 coils
photos.
(y) ET alternator and AC coils.

primary resistance should be 2-3 ohms,.......my new coil shows 1.3ohms!
Mmmm ...

As Terry's posted, the electrics are basically '6V' (as opposed to '12V') - reason I stress "basically" is actual Volts at any given time depend on engine/rotor speed and electrical load.

Being ET/AC, I'm not as familiar with the system as DC; '6V' DC coils would have a primary resistance between 1.5 Ohms and 2 Ohms ('12V' DC coils would have a primary resistance between 3 Ohms and 4 Ohms). AC coils similar, "1.3ohms" seems not unreasonable; "2-3 ohms" seems less likely?

still think 11.4K (each coil), seems excessive.
Mmmm ... certainly would be questionable for a DC coil, which normally have a secondary resistance around 5-7 KOhms.

the supplier
assures me that plenty of people have had these coils with no problems!
Mmmm ... aka "MRDA" = Mandy Rice Davies Applies = "He would say that, wouldn't he?". :D

[the supplier] suggests I check my stator and magnets. It does make sense but I'd like to suss this coil situation first.
Nevertheless, he might be right. Problem is you're dealing with components that're well over half-a-century old, and weren't great when new. :( Rotor magnetism in particular attenuates with age, never mind as Terry's pointed out Lucas encapsulated stators to isolate the thin coil wires from vibration and knocks ...

One thing I notice in your photos., are the plug caps resistor type (usually 5 KOhm)? If so, ditch 'em for non-resistor caps.

it may be more appropriate to try 12 Volt coils.
Mmmm ... source of '12V' AC coils?

Even when working correctly, the 6 volt lighting system doesn't have a lot going for it
Amen.

change the electrics to 12 Volts,
There's a wee bit more to it than Terry suggests ... DC wiring is entirely different; if the bike's existing wiring is contemporary with the ET alternator, modifying it to attach new alternator, reg./rec., blah is likely to be a waste of time for the few pennies saved on new wire.

standard RM21 alternator stator and rotor.
The RM21 wasn't "standard" on '66 DC bikes. Pattern parts are still available but are equally useless for road conditions in the third decade of the 21st century. RM21 was superseded as far back as 1978 by the 3-phase RM24. New alternator prices are much of a muchness irrespective of power output, 'high output' version of the RM24 would fit in place of your bike's ET alternator and provide much more power even at low rpm.

you still have the points and condensers.
the Auto Advance Unit on those bikes had a quite limited advance (5 camshaft degrees
... one of ET's problems. If you change the electrics to DC but hang on to points-'n'-condensers, replace the ET AAU with a DC one?

Hth.

Regards,
 

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Hi,
'6V' DC coils would have a primary resistance between 1.5 Ohms and 2 Ohms ('12V' DC coils would have a primary resistance between 3 Ohms and 4 Ohms). AC coils similar, "1.3ohms" seems not unreasonable; "2-3 ohms" seems less likely?
The Lucas Motor Cycle Electrical Equipment Service Manual, manual page 12, .pdf page 13, has a description of ET. From that:-

The alternator [stator] designed for A.C. ignition has the ignition generating coils connected in series with each other and with the primary winding of a special ignition coil, model 3ET.

This special ignition coil employs a closed iron circuit and has a primary winding whose impedance is closely matched to that of the ignition generating coils of the alternator [stator].
found out the primary resistance should be 2-3 ohms,.......my new coil shows 1.3ohms
Where did you "find out" the primary resistance should be 2-3 ohms? According to the LMCEESM, either that, or the 1.3 Ohms primary resistance of your new coils, is only correct if it is "closely matched to" the Ohms between the end of your bike's stator Brown wire and the end of the Black/White or Black/Yellow wire (Triumph C-range workshop manual, ET wiring diagram .pdf page 239, manual page H25)?

Hth.

Regards,
 

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Discussion Starter · #9 ·
Hi Furbrain,

I can say fairly confidently that your bike looks like a 1966 T100SC ex South African Army bike. I worked on them during my national service in South Africa, in the Technical Services Corp (equivalent of REME in UK). They indeed had ET ignition and I remember those open ET ignition coils with their translucent encapsulation clearly.

The original ET ignition coils are specifically for a higher voltage AC ignition system and are not the same as the usual 6 Volt coils. If you can't get the correct coils, taking into account the 2-3 Ohms that you say the primary windings on the original coils read, it may be more appropriate to try 12 Volt coils.

With regard to the alternators used on these bikes, what I specifically remember is how many of the 5 wire alternator stators used on those bikes, burnt out their lighting windings. The problem seemed to be that for daytime running, the lighting coils ran unloaded and with the combined effects of vibration on the open (non encapsulated) windings on those earlier stators and high open-circuit voltages, the coil insulation broke down, the windings short circuited and failed. In fact, most of the work I did on those bikes was replacing failed stators.

Even when working correctly, the 6 volt lighting system doesn't have a lot going for it either and can only power a fairly low wattage (6V 25/25W ?) headlight bulb. The original headlight on those bikes was 5" in diameter and took a BPF bulb. I can't be sure looking at the photo, but it looks likes yours may have been changed to a 7" unit.

If you still have an original (un-encapsulated) original 5-wire alternator, the best suggestion I can think of, is to bite the bullet, cut your losses and change the electrics to 12 Volts, by fitting a standard RM21 alternator stator and rotor. You will need a regulator rectifier, but if you don't want to fit a battery, you should be able to use a large capacitor (4700 micro Farad 25 Volts) instead of a battery, if you still have the points and condensers. You will of course need 12 Volts ignition coils and light bulbs.

As a side-note, I seem to remember that the Auto Advance Unit on those bikes had a quite limited advance (5 camshaft degrees seems to spring to mind) compared to the regular 12 Volt bikes with their 12 degrees. That should still be okay if its working - I remember them sticking and failing to advance quite often, unless the shaft inside the points cams was regularly oiled.

The choke on the monobloc carb was a spring return arrangement directly on the carb top, that was pulled down to put the choke "on". I don't remember it ever being needed. Tickling the carb was normally all that was needed to get it going.

Terry
Hi Terry,
Thank you very much for your obvious expertise and knowledge of my bike. Fascinating to find out where it had originally come from. I did wonder about the petrol tank because it didn't look standard?.
I bought the bike from Johannesburg. It hadn't run for 7 years and was just standing in a garage for this time. Apparently it had full restoration before this!.Some things had gone a bit rusty. I replaced all connectors and checked wiring for any breaks.
Will point out now that my knowledge of tech stuff is limited. Changing things to 12v?????....... stators, windings, .........to be honest this could be more than I understand and have extremely limited knowledge of electrics.
I am however very practical and, at least at this point, will not give up.
Step by step!.
I know I'm close!. With a brand new set of plugs it will start first kick!. (NGK b6es).
On the odd occasion I've blipped the throttle and it sounds strong!. After that it starts running lumpy . Check the plugs and they are sooty black!.
It seems as if the spark produced is not enough to burn all the fuel!. This is why I'm wondering if the coils are compatible? (Supplier says he has had no other people that have had problems with these aftermarket coils).
I'm still not convinced!.
Each coil reads 11.4K Secondary and 1.4ohms Primary. My Triumph manual recommends Primary to be 2-3 ohms!. I cannot find what the recommended Secondary value should be!.
Before getting into other things that could be the problem I would like to understand the coil and how different resistance could affect the strength of the spark.

I've seen quotes on internet that recommended Secondary value should be around 5/6K and we know Primary is 2-3ohms.
If my new coils are reading(multimeter) almost double the resistance on Secondary, my logic is telling me that power to plug is seriously compromised?¿??????...........…. or do I have this idea wrong??????.
It's a shame (for me) you don't live in the Western Cape.

Thanks for your time and patience.
Hi,


As Terry's posted, one of the batch supplied to the SA army.


They were built at the beginning of the '66 model year, which was the first year of the 'eyebrow' tank badges and 'pleated' (ribbed) seat covers; I'll guess the "earlier" ones had nominally-'65 tank badges and seat covers, "later" ones had the new-for-'66 bits?


Lucas/Triumph never supplied an ignition switch with ET electrics. ET works like a magneto, which didn't have an ignition switch plus I suspect the army hardly wanted ignition keys to keep track of and would immobilise a bike possibly miles from anywhere if lost by a careless squaddie.


(y) ET alternator and AC coils.


Mmmm ...

As Terry's posted, the electrics are basically '6V' (as opposed to '12V') - reason I stress "basically" is actual Volts at any given time depend on engine/rotor speed and electrical load.

Being ET/AC, I'm not as familiar with the system as DC; '6V' DC coils would have a primary resistance between 1.5 Ohms and 2 Ohms ('12V' DC coils would have a primary resistance between 3 Ohms and 4 Ohms). So your "1.3ohms" seems not unreasonable; "2-3 ohms" seems unlikely.


Mmmm ... certainly would be questionable for a DC coil, which normally have a secondary resistance around 5-7 KOhms.


Mmmm ... aka "MRDA" = Mandy Rice Davies Applies = "He would say that, wouldn't he?". :D


Nevertheless, he might be right. Problem is you're dealing with components that're well over half-a-century old, and weren't great when new. :( Rotor magnetism in particular attenuates with age, never mind as Terry's pointed out Lucas encapsulated stators to isolate the thin coil wires from vibration and knocks ...

One thing I notice in your photos., are the plug caps resistor type (usually 5 KOhm)? If so, ditch 'em for non-resistor caps.


Mmmm ... source of '12V' AC coils?


Amen.


There's a wee bit more to it than Terry suggests ... DC wiring is entirely different; if the bike's existing wiring is contemporary with the ET alternator, modifying it to attach new alternator, reg./rec., blah is likely to be a waste of time for the few pennies saved on new wire.


The RM21 wasn't "standard" on '66 DC bikes. Pattern parts are still available but are equally useless for road conditions in the third decade of the 21st century. RM21 was superseded as far back as 1978 by the 3-phase RM24. New alternator prices are much of a muchness irrespective of power output, 'high output' version of the RM24 would fit in place of your bike's ET alternator and provide much more power even at low rpm.


... one of ET's problems. If you change the electrics to DC but hang on to points-'n'-condensers, replace the ET AAU with a DC one?

Hth.

Regards,
Many thanks for the input. Unfortunately for me it all sounds a bit daunting. I still need to be sure that it isn't just something like a short in the whole circuit. I am not so confident with wiring/testing etc.

The whole post so far has been very informative and interesting however I was hoping someone could answer one of my original questions;
If a coil has substantially more resistance than required ................ will there be a weaker spark at the plug?.
Hi,

Mmmm ... several things in your post make me suspicious:-


What carburettor? If it's an Amal, are you actually using the 'choke'? Reason I ask is if you aren't familiar with Amals, the 'choke' works the opposite way to most (all?) other carbs., particularly if it's cable operated - Amal, slack wire is 'choke on', tight wire is 'choke off'. If the bike has an air cleaner fitted, remove it and check the 'choke' (more correctly "air slide") is actually rising when any choke cable's tightened or lever's operated.


If your T100 has ET ignition, it cannot use one coil (singular, with two HT leads?). Like any alternator, the special ET one generates AC (Alternating Current); however unlike other alternators, the AC is not rectified, so the coils (2) must be both separate for each cylinder and special AC ones.

Aside, if you have a single DC coil with two HT leads and you are measuring between HT and LT, yes it will appear high-resistance; unlike ignition coils with a single HT lead, there isn't any physical connection between HT and LT.


If you bike's ignition really is ET (alternator stator has five wires), some modern dirt bikes use AC coils; ET confirmed, I'll look up the sources I know for suitable modern coils.

"Picture's worth a thousand words" etc., could you take and post photos. of your bike, the original coils and the coil(s) you're trying to use now?

Just as a matter of interest, is/are your bike's engine and frame number/s between H40528 and H40868?

Regards,
Hi Stuart,
Would you be able to source the right coils now we know it's definitely a phone home bike. Can't see any reason for going any further into the depths of the engine before trying the proper coils. Appreciate your help.
Hi,

The Lucas Motor Cycle Electrical Equipment Service Manual, manual page 12, .pdf page 13, has a description of ET. From that:-



Where did you "find out" the primary resistance should be 2-3 ohms? According to the LMCEESM, either that, or the 1.3 Ohms primary resistance of you new coils, is only correct if it is "closely matched to" the Ohms between the end of your bike's stator Brown wire and the end of the Black/White or Black/Yellow wire (Triumph C-range workshop manual, ET wiring diagram .pdf page 239, manual page H25)?

Hth.

Regards,
Good morning. Please hold the bus!!!!!!!.
Turns out I've been measuring the coil with 5K suppressed plug cap on,...........Duh.
Will try the bike again with normal plug Caps!. (Good call Terry!).
Will let you know the outcome.
Thanks for your patience.
Attached shows where I got Primary values from the handbook.
 

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If it “starts right up” with one kick then the spark is good.
Seems to me it’s running extremely rich. You don’t have the choke on do you? On these old Amal carbs the choke is actually on when the cable is slack and off when the cable is tight.
 

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Hi Furbrain, where are you based? I've got an ex SA military T110 close to JHB. Parts are not easy to get in SA. The local guy essentially has a Wassel Catalogue and that's it.... not a great amount of detailed knowledge. With the problems at the South African Post office, I brought most stuff over in suitcase when I visit my folks.
 

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Hi,
Turns out I've been measuring the coil with 5K suppressed plug cap
Will try the bike again with normal plug Caps!. (Good call Terry!).
are the plug caps resistor type (usually 5 KOhm)? If so, ditch 'em for non-resistor caps.
You're welcome ...

seen quotes on internet that recommended Secondary value should be around 5/6K
... if you subtract the plug caps' 5 KOhm from the "11.4" KOhm you've been seeing ... ;)

My Triumph manual recommends Primary to be 2-3 ohms!
Attached shows where I got Primary values from the handbook.
Actually, that's the Triumph Workshop Manual ...:-

. unfortunately, the Section title is poorly-worded - "SECTION H2 COIL IGNITION SYSTEM" is DC - "MA6" and "MA12" in your screenshot are respectively '6V' and '12V' DC coils - but note the illustration on the left of your screenshot shows completely different coils from the ones on your bike (also, the Ohms values are misprinted :oops:);

. the Manual Section you require is "H6 A.C. IGNITION (E.T.) AND A.C. LIGHTING SYSTEMS".

brand new set of plugs it will start first kick!. (NGK b6es).
B6 is too 'hot', B7 is the equivalent of the Champion N4 detailed in Triumph Workshop Manual. If you can acquire them with thin centre electrodes - B7EV, B7EVX, B7EG or B7EIX - so much the better; avoid any designated BR7xxx, they have an internal resistor.

If it “starts right up” with one kick then the spark is good.
Mmmm ... when the engine starts, the electrical components are cool or cold; when they're working, they heat up, the problem being experienced might be one or more components heating up and failing. :(

starts running lumpy . Check the plugs and they are sooty black!
bike
hadn't run for 7 years and was just standing in a garage for this time.
Some things had gone a bit rusty.
Consider replacing all carb. jets, corrosion could well have enlarged them, next-size or bigger jet orifices won't be visible to the naked eye. The rich running could simply be enlarged pilot and/or needle jet; all jets are brass, the needle is steel, particularly wears the needle jet, makes it larger = rich mixture.

This is why I'm wondering if the coils are compatible?
Given what's in the aforementioned Lucas manual, have you measured the stator ignition coils' resistance as I described?

The problem is the Lucas manual is not clear whether the ignition coil primary resistance should be the same as each stator coil, or the two stator coils together - they're connected 'in series', which means their individual resistances are cumulative.

If you haven't done so already, measure the resistance of the two pairs of stator ignition coils as I described, post your meter readings? Risking telling you something you know already, as these values are around 1~2 Ohms, you need a very 'good' (= expensive?) multi- or Ohm-meter to read them accurately.

Hth.

Regards,
 

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Discussion Starter · #13 ·
Hi,


You're welcome ...


... if you subtract the plug caps' 5 KOhm from the "11.4" KOhm you've been seeing ... ;)


Actually, that's the Triumph Workshop Manual ...:-

. regrettably, you've misinterpreted the Manual, "SECTION H2 COIL IGNITION SYSTEM" is DC - "MA6" and "MA12" in your photo are respectively '6V' and '12V' DC coils (nevertheless, the Ohms values are misprinted :oops:);

. the Manual Section you require is "H6 A.C. IGNITION (E.T.) AND A.C. LIGHTING SYSTEMS".


B6 is too 'hot', B7 is the equivalent of the Champion N4 detailed in Triumph Workshop Manual. If you can acquire them with thin centre electrodes - B7EV, B7EVX, B7EG or B7EIX - so much the better; avoid any designated BR7xxx, they have an internal resistor.


Mmmm ... when the engine starts, the electrical components are cool or cold; when they're working, they heat up, the problem being experienced might be one or more components heating up and failing. :(


Consider replacing all carb. jets, corrosion could well have enlarged them, next-size or bigger jet orifices won't be visible to the naked eye. The rich running could simply be enlarged pilot and/or needle jet; all jets are brass, the needle is steel, particularly wears the needle jet, makes it larger = rich mixture.


Given what's in the aforementioned Lucas manual, have you measured the stator ignition coils' resistance as I described?

The problem is the Lucas manual is not clear whether the ignition coil primary resistance should be the same as each stator coil, or the two stator coils together - they're connected 'in series', which means their individual resistances are cumulative.

If you haven't done so already, measure the resistance of the two pairs of stator ignition coils as I described, post your meter readings? Risking telling you something you know already, as these values are around 1~2 Ohms, you need a very 'good' (= expensive?) multi- or Ohm-meter to read them accurately.

Hth.

Regards,
I am impressed with your knowledge!. Many thanks for clearing these points (no pun intended).
I have renewed vigor!. Can't work on bike for a few days but will update as and when.
I have done what you suggest re carb.
New jets, main and needle, new needle which didn't make much difference!. Never give up......never surrender. Life is a learning curve!.
Have a great day and regards to all.
Re the pic......... measuring with suppreser.......Duh🤪
 

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Hi Furbrain

I have found this thread on Britbike. The whole thread is specifically about ET ignition, but it goes VERY deep into the subject and will take a lot of study, but if you can take your time reading (and re-reading it), there is a lot of information there:

Repairing an ET Ignition System

Terry
 

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Hi,


You're welcome ...


... if you subtract the plug caps' 5 KOhm from the "11.4" KOhm you've been seeing ... ;)


Actually, that's the Triumph Workshop Manual ...:-

. regrettably, you've misinterpreted the Manual, "SECTION H2 COIL IGNITION SYSTEM" is DC - "MA6" and "MA12" in your photo are respectively '6V' and '12V' DC coils (nevertheless, the Ohms values are misprinted :oops:);

. the Manual Section you require is "H6 A.C. IGNITION (E.T.) AND A.C. LIGHTING SYSTEMS".


B6 is too 'hot', B7 is the equivalent of the Champion N4 detailed in Triumph Workshop Manual. If you can acquire them with thin centre electrodes - B7EV, B7EVX, B7EG or B7EIX - so much the better; avoid any designated BR7xxx, they have an internal resistor.


Mmmm ... when the engine starts, the electrical components are cool or cold; when they're working, they heat up, the problem being experienced might be one or more components heating up and failing. :(


Consider replacing all carb. jets, corrosion could well have enlarged them, next-size or bigger jet orifices won't be visible to the naked eye. The rich running could simply be enlarged pilot and/or needle jet; all jets are brass, the needle is steel, particularly wears the needle jet, makes it larger = rich mixture.


Given what's in the aforementioned Lucas manual, have you measured the stator ignition coils' resistance as I described?

The problem is the Lucas manual is not clear whether the ignition coil primary resistance should be the same as each stator coil, or the two stator coils together - they're connected 'in series', which means their individual resistances are cumulative.

If you haven't done so already, measure the resistance of the two pairs of stator ignition coils as I described, post your meter readings? Risking telling you something you know already, as these values are around 1~2 Ohms, you need a very 'good' (= expensive?) multi- or Ohm-meter to read them accurately.

Hth.

Regards,
Hi Stuart/forum, I have another question ...(oh no I hear you groan).
Same bike.......... manual states N4 Champion plugs with .5mm gap!.
If I use equivalent NGK B7whatever.............do I 'gap' these to .5mm also?.
Out the box they are around .65mm.
.5mm sounds a bit small but maybe it's because the power generated is not great and can't jump a large ( normal gap)?????.
@Furbrain
Not sure if you saw this.
Hi Furbrain

I have found this thread on Britbike. The whole thread is specifically about ET ignition, but it goes VERY deep into the subject and will take a lot of study, but if you can take your time reading (and re-reading it), there is a lot of information there:

Repairing an ET Ignition System

Terry
Many thanks Terry. Will digest.
I appreciate the guidence.
 

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Hi Stuart/forum, I have another question ...(oh no I hear you groan).
Same bike.......... manual states N4 Champion plugs with .5mm gap!.
If I use equivalent NGK B7whatever.............do I 'gap' these to .5mm also?.
Out the box they are around .65mm.
.5mm sounds a bit small but maybe it's because the power generated is not great and can't jump a large ( normal gap)?????.


Many thanks Terry. Will digest.
I appreciate the guidence.
Hi Furbrain,
I'm using NGK B7ES plugs on my Daytona 500 gapped at the recommended 0.020" 0.5mm and its starts easily and idles well.

Terry
 

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Hi
seen quotes on internet that recommended Secondary value should be around 5/6K
From:-
. post 633721:-
Three electrical leads come from both versions of the ET coil; two wires
and one internal spike to make contact to the spark plug lead when it is pushed into the hole.
the resistance between the two wires should be ~1/2 Ohm and the resistance between either of those wires and the internal high tension connection should be approximately 5-6 kiloOhms. If your coil has approximately these values it probably is fine. However, if either value differs significantly (most likely, the high tension circuit having infinite resistance), you will need a new coil.
... so I'm a little concerned the 1.3-Ohm primary resistance of your new coils might not be a close-enough match the stator coils' resistance?

... btw, note also the suggested alternative Japanese AC coils in this post.

. post 646426:-
can i use the 6ac points plate instead of the 4ac type with the ET IGNITION
Also ,can i eliminate the condensers that are mounted on the points plate, still using only the long ones mounted on the coils
. post 646444:-
Yes, the 6ac is a direct replacement. Ideally, you will have condensers at the coils and across the points. Electrically, it might look like having them at the coils is the same as having them at the points but the inductance of the wire between the locations add reactance, i.e. somewhat reduces the effectiveness of the condenser as providing a low resistance alternative path for the current when the points open. The bike should run but the lifetime of the points will be reduced to some degree due to increased arcing.
This won't be clear to you, in part because "4ac" and "6ac" are misprints ... :rolleyes:

. Your bike at least originally had a Lucas 4CA points plate. If it still does:-

.. One disadvantage is the condensers are mounted on the points plate. As "Magnetoman" explains, brilliant for the points; in reality, engine heat buggers the condensers in short order, then not brilliant for anything ...

.. Second disadvantage is only one set of points is adjustable independently of the plate, so timing between the cylinders can need to be a compromise - both cylinders slightly out rather than one correct and one wildly-out. But neither is what you want when ET spark timing is critical ... :(

. The 6CA points plate is only a couple of years later, both sets of points are adjustable independently on the plate, the condensers are mounted in a rubber case hanging down from the front tank mounting. All standard parts from later twins. (y)

using NGK B7ES plugs on my Daytona 500 gapped at the recommended 0.020" 0.5mm
+1. When you read the Repairing an ET Ignition System thread, you'll see "Magnetoman" has posted he uses the common 0.018" (~0.45 mm.) magneto points gap.

Hth.

Regards,
 

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Hi Furbrain,

Here's another link worth having a look at:

Lucas ET Ignition Unraveled

It looks like those ignition coils you have may be Emgo part number 24-71532 "Universal" coils. They are supposedly "suitable for 6 Volt, 12 Volt and CD systems", but ET systems are not mentioned. Information elsewhere specs them with a 1 Ohm primary DC resistance, which more or less ties up with what you measured.

You got 1.3 Ohms, before taking the reading, did you touch the meter leads together to take the resistance of the meter leads alone, to subtract it from the reading you got?

On a AC system like this, taking a DC resistance reading is of very limited value, what matters is Impedance (AC resistance), unfortunately your meter cannot measure that to compare the coils. However, if it becomes necessary later, there is a fairly basic method to measure it, but we can go into that later if needed.

Both the the link above and the previous one seem to indicate that the Emgo coils will work on an ET system.

Its also interesting that the ET system uses 2 condensers for each cylinder, one at the points and another at the coil in each case. It is also mentioned on the above site, that both are needed for this system to work.

If the condensers you have are original, are they still working, I wonder? Might be worth checking!

A simple test to give you some indication - the condensers will need to be disconnected for this.

Set your DVM to 200k on the resistance scale.

Connect the meter leads to the condenser - what you should see, is an initial low resistance, which increases as it charges up and then settles at a very high value or even above what the meter can read. This should be a quick rise.
If the reading stays low, the condenser is no good.

If it passes this test, change the range to 200 Ohm scale and use the meter to "charge" the condenser for a few seconds.

Remove the leads and switch the meter to the 20 Volt DC voltage range - After a few seconds, by the time you have done this, touch the leads on the condenser and see if it has retained any of the charge. What you should see, is an initial voltage that then reduces as the meter discharges the condenser.

If it passes this test, charge it again on the 200 Ohm resistance setting and try leaving it for a minute or two, before checking the voltage again as before. If it passes this test, it is in good condition.

These simple tests will not indicate the actual capacitance of each condenser, but they will show if they are still working.

Terry
 

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Hi,
looks like those ignition coils you have may be Emgo part number 24-71532 "Universal" coils. They are supposedly "suitable for 6 Volt, 12 Volt and CD systems", but ET systems are not mentioned.
Both the the link above and the previous one seem to indicate that the Emgo coils will work on an ET system.
Wrote my earlier text in a bit of a rush before I went to work. Thinking about it on a 160-mile round trip mostly with cruise control on, I realised "suitable for 6 Volt, 12 Volt and CD systems" was written by an electrical illiterate, it's impossible. Quick internet search doesn't find the a link to an actual Emgo webpage, so dunno whether the sellers are parroting bum information from Emgo or inventing it themselves.

The impossibility has to do with primary resistance. @Furbrain has already measured 1.3~1.4 Ohm, that's high for a CDI coil, marginal for a '6V' (DC) coil but wa-aa-ay to low for a '12V' coil.

The primary criterion for a DC coil switched by points (or points-replacement EI) is the primary draws 3~4 Amps when the rated Volts are applied across it. Ohm's Law (E=IR, Volts = Amps multiplied by Ohms) says a '6V' coil must have primary resistance between 2 Ohms and 1.5 Ohms respectively, a '12V' coil must have primary resistance between 4 Ohms and 3 Ohms respectively ... i.e. take a '6V' coil and apply 12V across its primary, it'll draw between 6 and 8 Amps ... it'll get very hot just before it burns out ... :oops:

Otoh, CDI coils are charged with a very short (milliseconds) burst of relatively-high Volts (400V?); because the charge duration is very short, primary resistance would be a hindrance, they don't heat up because the charge duration is so short.

In addition, in Repairing an ET Ignition System, "Magnetoman" states CDI coils have a much lower secondary resistance - ~2.5 KOhms, vs. the 5~6 Kohms of an ET coil, that's been measured and posted earlier in the thread.

Its also interesting that the ET system uses 2 condensers for each cylinder, one at the points and another at the coil in each case. It is also mentioned on the above site, that both are needed for this system to work.
Uh-uh, ET doesn't "need" four condensers to work; certainly in '66 and '67, both AC and DC systems show four condensers.

Lucas put the condensers on the 4CA points plate; as "Magnetoman" explained, that is indeed desirable for the primary reason of protecting the points when opening and closing, irrespective of whether the electrics are AC or DC. As I posted above, snag with that arrangement is Lucas failed to protect the condensers from engine heat; :oops: 4CA points-plate condensers have always been notorious for their short lives.

Fifty-plus years on, it's hard to know the real reason for four condensers (two on the points plate and two external), possibly simply to save scrapping a large number of 4CA points plates when the balls-up became apparent? Once the 4CA was superseded by the 6CA, there are only the two external condensers; as "Magnetoman" explains, not such good protection for the points but, given the external condensers' increased longevity, that the points were protected for longer was considered an acceptable compromise?

Hth.

Regards,
 
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