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ET Ignition - Exlplained #418553
02/14/12 5:24 am
02/14/12 5:24 am
Joined: Mar 2007
Posts: 215
Southern California
Geoff Patrick Offline OP
Life member
Geoff Patrick  Offline OP
Life member

Joined: Mar 2007
Posts: 215
Southern California
I have two ET Ignition Cubs and I am working on a Cub Scrambler that I also want to equip with ET ignition. I recently saw on eBay, someone selling a "TRIUMPH TIGER CUB 12 VOLT CONVERSION KIT". There was a a detailed explanation of the benefits and how this kit, which consisted of a Wassell rotor/stator, was a "STRAIGHT BOLT ON CONVERSION REQUIRING NO SPECIAL ADAPTATION OR MACHINING". I asked the seller specifically if this kit worked in an ET system and he confirmed the fit. I thought that with the scarcity of genuine Lucas ET alternators, this would be a great solution for the scrambler Cub I am building with side-points and ET ignition coil, no lighting.

I bought and have recieved the Wassell alternator and it now leaves me with several questions to fill in my understanding of the ET system;

The Wassell stator has only two wires. Is it possible that this 12v alternator stamped "10A" would be made to power the ET ignition & lighting circuits through one output wire of the stator assuming one wire is ground?

The keyway position in Wassell WW10105P rotor hub does not correspond to the keyway position of a Lucas 54212006 rotor hub with repect to the nearest magnet. Is it possible that this rotor could still work with an ET ignition?

What is unique about the ET ignition coil?

What should I consider before using a 12v alternator with the 6v ET ignition coil?

Does this alternator seem like a direct 12v replacement for a Lucas 47197B or 47173B alternator in an ET Cub?

Thanks!

gp

Attached Files Wassell_Alt.jpg

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Re: ET Ignition - Exlplained [Re: Geoff Patrick] #418560
02/14/12 6:24 am
02/14/12 6:24 am
Joined: Nov 2011
Posts: 4,735
U.S.
Magnetoman Online content

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Magnetoman  Online Content

BritBike Forum member

Joined: Nov 2011
Posts: 4,735
U.S.
Originally Posted By: Geoff Patrick
The Wassell stator has only two wires. Is it possible that this 12v alternator stamped "10A" would be made to power the ET ignition & lighting circuits through one output wire of the stator assuming one wire is ground?

The keyway position in Wassell WW10105P rotor hub does not correspond to the keyway position of a Lucas 54212006 rotor hub with repect to the nearest magnet. Is it possible that this rotor could still work with an ET ignition?

What is unique about the ET ignition coil?

Does this alternator seem like a direct 12v replacement for a Lucas 47197B or 47173B alternator in an ET Cub?

Unfortunately, the short answer is 'no', this stator and rotor won't work on an ET system.

I'm sure you will get replies saying you should convert your ET system to a conventional one, but the ET has several advantages to recommend it. Not least of which is, you don't need a battery. However, it requires careful setup to work, and much of its reputation is due to people not understanding what needs to be done.

Briefly, a proper ET rotor is needed, because in order for the ignition system to work the rotor has to be keyed to the crankshaft so that its magnets are passing by the ET stator coils at just the moment the points open. Such timing of the rotor to the points isn't needed with a conventional system. The magnets in both types of rotors are the same, but the orientation of the keyways differ, and the difference is critical.

Next, a proper ET stator is needed, which uses a different number of windings (and hence a different voltage) for the ignition coils than for the lighting coils.

Finally, a proper ET high tension coil is needed. Here, there's a problem, because it seems Lucas must not have completely cleaned the solder flux from the tiny wires, and as a result many of these coils are dead. However, you can easily determine with an ohmmeter whether yours is still OK. And, even if it's not, Honda coils from certain bikes made in the 1970s are direct substitutes.

But, I'm getting ahead of the story. You'll need to get the correct rotor and stator for your bike before any of the rest of this matters.

Re: ET Ignition - Exlplained [Re: Magnetoman] #418562
02/14/12 6:35 am
02/14/12 6:35 am
Joined: Jul 2007
Posts: 451
redondo beach, ca
Bob G Offline
BritBike Forum member
Bob G  Offline
BritBike Forum member

Joined: Jul 2007
Posts: 451
redondo beach, ca
The ET system is an AC "magneto" with the components spread over the bike, (and with lighting coils) instead of in a single package. Same setup the Japanese used on a lot of singles in the 70s and 80s.
I would prefer the DC setup with the capacitor if I wanted to run without a battery. I had my fill of the ET system with a round barrel Victor.


Bob Gregor
Re: ET Ignition - Exlplained [Re: Geoff Patrick] #418651
02/14/12 5:32 pm
02/14/12 5:32 pm
Joined: Mar 2007
Posts: 215
Southern California
Geoff Patrick Offline OP
Life member
Geoff Patrick  Offline OP
Life member

Joined: Mar 2007
Posts: 215
Southern California
I am a Lucas ET Ignition Fan. Both of my road-going Mountain Cubs have original Lucas ET systems and they work great. I love having a full lighting system and no battery. I have had very little touble with exception to finding replacement Lucas ET alternators. Fortunately, I was able to successfully repair an un-encapsulated stator with fresh wires.

I really should have known better than to believe that there was a "silver bullet" alternator that would single-handedly convert the system to 12v for only $150! I will build my scrambler with a genuine Lucas ET system.

Thanks for the info everyone!

gp

Attached Files Stator74988a.jpg

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Re: ET Ignition - Exlplained [Re: Geoff Patrick] #418662
02/14/12 6:50 pm
02/14/12 6:50 pm
Joined: Nov 2011
Posts: 4,735
U.S.
Magnetoman Online content

BritBike Forum member
Magnetoman  Online Content

BritBike Forum member

Joined: Nov 2011
Posts: 4,735
U.S.
Originally Posted By: Geoff Patrick
I am a Lucas ET Ignition Fan.

I, too, have long been a fan of this system. I have it on two of my bikes, one that I've had for over 40 years, and the other 15 years. In all that time I've had two failures, one that is specific to the ET system. As I mentioned in my previous post, unfortunately there seems to be a defect in the high voltage side of the coils, that I speculate is caused by residual acid flux slowly eating through the very fine wire. The resistance of the primary should be 0.6 Ohms, and that of the problematic high tension side 5.2-5.6 kOhms. With a standard ohmmeter it's hard to distinguish 0.6 Ohms from a dead short, but my experience is that such a short is unlikely. If your secondary is ~5 kOhms you should be fine (for now).

Luckily, this is easily solved by replacing the Lucas coil with one of several coils used on Hondas and Yamahas. The same model number was used on several bikes, with and without ET-type coils, but to give one specific example, those coils were used on a 1974 Honda XL125. The part no. is 30500-355-003, superceded by 30500-950-405. This coil comes with a condenser riveted to the laminated housing. Leave the condenser in place, cut the wire, and attach your own replaceable external condenser between the wire and ground instead. Don't be tempted to drill the old condenser out -- the laminations need to be left intact.

The other failure I had was with an unencapsulated stator. However, this is a problem equally likely to happen to a non-ET stator. The good thing about unencapsulated stators is that it is usually easy to repair them. The bad thing is, they are more susceptible to failure. A BSA service bulletin from the early '60s recommended that racers encapsulate the wiring by dipping their stators in glyptol. What most people may not appreciate is that the oscillating magnetic field due to the motion of the rotor subjects the coils to rather large oscillating forces. If any of the coils in the stator is free to move at all, this eventually causes a wire or solder joint to break.


Moderated by  John Healy 


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