Powerdynamo Mag-Dyno

A Nut

Well Known and Active Forum User
VOC Member
You can adapt a Lucas MO1 to fit an A single. There is one fitted to the club bike "Nigel" I cut the gearcase from the end and milled 10mm off the base to bring the spindle height down to 35mm. The dynamo drive consists of a pair of pulleys and a 100XL toothed belt. It is a very tight fit and needs a split cover fabricated to fit the points. If you can get hold of a prewar Lucas magdyno with ring cam (nearly as rare as a Miller or BTH) they are shorter and are an easier fit. I have this conversion on my A Comet. The late Bob Stafford described how to fit a Lucas MO1 magdyno without altering the drive but it meant cutting a slot in the platform to allow the Lucas fibre pinion to sit down through it. Forty Years On page263 article 45. The advantage of modifying the Lucas magdyno to belt drive is that you don't have to modify anything on the engine.
Brian
 

Chris Launders

Well Known and Active Forum User
VOC Member
If you have a decent dynamo you could do what I have done until I could afford a mag rebuild for my JAP V-twin.
Using a magdyno fitted with the early cam ring type end and a 50 degree cam ring I took the windings off a the armature, fitted a single slip ring, modified a pickup with an electric drill brush set up and ran a wire from the slip ring to the points.
I had a twin plug coil and condensor mounted up under the tank and for the wire from the coil to the mag pickup I used copper HT lead and obviously a switched feed to the coil.
This gave me coil ignition with a manual adv/ret and with the "live" wire and a dummy one from the unused pickup was indistinguishable from an actual working magdyno with the added bonus of a good spark at any revs.
To do a single would be much easier.
 

billirwinnz

Well Known and Active Forum User
VOC Member
I concur about the Power dynamo not producing a strong enough spark at kicking speed on an A. I had the same problem with the modern BTH unit. The Marelli magneto is a rotating magnet one and produces a much stronger spark than either a BTH or Lucas. I discovered this when testing a plug with an inbuilt resistor. The Marelli would fire it with a strong spark but the other two wouldn't. All have new coils.

I had a problem with a mag on an early Ariel four. The timing wasn't even (which gets exaggerated on the Ariel as the mag runs at engine speed) and the spark was poor. Rather than an expensive rewind I opted for a Thorspark coil conversion which works very well. It involves fitting a coil and replacing the points with a pickup and small rotor. Not difficult. Timing becomes spot on and the existing manual or ATD advance is retained. Available as 6 or 12v and draws only a claimed 1/4 amp so will run for hours even without battery charging. I hid the coil under the seat. https://www.sussexmotorcycles.com/t...les-22-to-80-degrees-Vincent-JAP-BSA-etc.html

Bill
 

Vincent Brake

Well Known and Active Forum User
VOC Member
i've looked at Thorspark as well, maybe the better route for me, as i don't want to know about all the magnetos and how they work.
Vape: there is one on an A twin, and was difficult to start, but now with carbie choke cables bit changed, it seems to work well for the last twenty starts.
 

MarBl

Well Known and Active Forum User
VOC Member
I opted for a Thorspark coil conversion which works very well.
Thanks for mentioning that alternative. I never heard of them before.

My Velocette Venom ran very well until its K1f armature failed. I tried the new BTH which worked fine for 1ml, started misfiring after about 2mls and failed after 5mls. After repairs it never ran reliably, making starting a pain and giving erratic ignition at low revs.
I was considering a Pazon as a replacement. I have a smartfire on my Rapide that starts and runs just fine.
Since I dont see any real advantage of all this expensive and fancy electronics, I now ordered a Thorspark right away. I like that simplistic approach. Hopefully the Venom will be back on the road until summer.
 

billirwinnz

Well Known and Active Forum User
VOC Member
The only drawback with the Thorspark that I encountered was timing it because unlike points you can't determine the exact point of firing statically. Starting from a roughly correct position they recommend using a timing disk and a strobe to get the exact timing but I had nowhere I could drive one from on the Ariel. I had to do it by trial and error. However it was very quick and easy to move the rotor until the timing was right. Much easier to find the right setting on a road test with manual advance and retard.
 

delboy

Well Known and Active Forum User
VOC Member
As this is the Series "A" category,- can this "Thorspark" be fitted to any "A" ignition units?
Delboy.
 

Vincent Brake

Well Known and Active Forum User
VOC Member
I am trying hard, to fit it in, (digitally now) will let you know.
I am in the process of identifying whats on by bike now...
 

billirwinnz

Well Known and Active Forum User
VOC Member
As this is the Series "A" category,- can this "Thorspark" be fitted to any "A" ignition units?
Delboy.
Yes for an A single. They can easily make rotors for any angle vtwin as it’s just a matter of where on the rotor the slots for the small magnets are machined. I don’t know how it’s set up for two cylinders but probably firing two coils simultaneously with a wasted spark. They advertise units to fit Vincents so I suggest you ask them.

The Ariel uses a 180 twin cylinder magneto with a distributor so a bit different.

Bill
 

vibrac

Well Known and Active Forum User
VOC Member
I guess that the Electronic BTH manufacturer can produce a 'Friday' unit, but in years of racing and road use of twin and single unitsI have never had one let me down. The latest racer has had the BTH replaced this year (after a successful season) with a Tri-spark unit mainly because with a rolling road we can program the ignition point and the advance curve to produce the most effective power at all revs for our Engine but thats a level of sophistication you would not notice going down to the chip shop.
 
Top