New Type BTH Magneto

[BigEd]

I think you may find that in the true sense of the word this is not a magneto but a system that has some kind of internal generator that powers an electronic spark system and if I recall it fires a lost spark so if one plug is disconnected it will still fire the lost spark to the other plug. Coincidentally, I did exactly that today on a new BT-H mag and with no ill effect!! It has external coils.

Dear Robert,
You are a brave "guinea pig" if you ran you magneto without the H.T. leads earthed. I personally would not run the magneto or any ignition system without the leads earthed for many of the reasons stated in previous posts in this thread.
The new BT-H doesn't have a wasted spark as there is only one "trigger" magnet on the rotor arm.

Re: Magneto Two quotes from the internet.
science.howstuffworks.com/magneto-info.htm says: An alternating-current generator that contains a permanent magnet. A magneto, unlike a generator that contains an electromagnet, requires no source of direct current for its operation.

Wikipedia Says: A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current.

 

[vibrac]

I do know that the new BT-H man changed the coils he offered and was selling the old ones cheap at last years Stafford show (1 year ago) so he has been thinking about it (he did tell me why he changed but my mind is blank) I bought a couple of the old ones my reasoning was if I have raced on the originals for years then taking a few spares around should cover me .In fact my new head on the Comet racer is single plugged at the moment (the old head was twin plugs) so I just left the second coil attached alongside and disconnected the wires (a ready to go installed spare)

 

[Albervin]

I think the new coils are a screw on rather than a push on so less likely for the lead to fall off.

 

[greg brillus]

Thanks Alyn, Yes it was one of those moments that gives you a real sinking feeling, but I was more than happy to help out and return you and your trusty Steed back on the road. To me it is one of the great things to help others in need, and what makes the people and the activities of the Vincent owners club the world over, so great. Once again thanks for the kind words, and happy Easter........Greg.

 

[vibrac]

Going back to the spark plug on the head theme I dont know how many times I wished I had a tool clip like this fixed to the engine but I just precariously balance the plug ,it falls off a few times I swear then finaly test the plug sort the problem and move on. One day I may remember when I have an engine on the bench...

 

[Robert Watson]

I was talking with Peter this AM about a unit for the A twin. It is NOT a magneto, just made to look like one. It is a Capacitor Discharge ignition (CDI) and in fact the unit he makes to replace an MD2 type runs on only one lead coming from the unit with the CDI box and coils mounted externally. He even goes so far as to put a dummy wire in and a dummy connection for the spark advance/retard cable. He says the base to shaft height is 45mm, and has been questioned by a customer whose is 35mm, so I am off to crawl under there and see if I can measure it! Or someone with an MD on the shelf could measure it for me!

 

[BigEd]

Dear Robert,
My posting about the definition of a magneto was not put there to be argumentative but to be informative. The new BT-H units are advertised and sold magnetos. They do, as the definitions say, have an alternating-current generator and requires no source of direct current for its operation. The product of the generator is indeed processed by a CDI unit.

 

[Robert Watson]

I was only pointing out t hat they were not truly a magneto as in Lucas or old BTH and so the rules of voltage at the plugs and other magneto truths really don't apply. Anyway. I have ordered a suitable one from BT-H Components so my search for a spare is over.

 

[Chris Launders]

M/D armature height is 45mm robert (mine are anyway)
Chris.

 

[BigEd]

I was only pointing out t hat they were not truly a magneto as in Lucas or old BTH and so the rules of voltage at the plugs and other magneto truths really don't apply. Anyway. I have ordered a suitable one from BT-H Components so my search for a spare is over.

Glad that Peter is going to build you a unit for your "A" twin. There are a few of these units out there on "A" twins. Arthur Farrow has one on his "A" twin and that seems to be performing very well when he attended Bob Stafford's funeral.