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post #11 of 14 (permalink) Old 11-14-2012, 03:32 PM
Supersport 400
Main Motorcycle: Triton 650
Join Date: Nov 2012
Location: Isle of Wight, UK
Posts: 99
Put a Lucas 3-phase kit on my pre-unit 650 in 1981, to ensure it could cope with a Lucas-Rita magneto conversion. Ran for ~4 years with a big electrolytic capacitor instead of battery, just had to turn headlights off at tickover.
The alternator still works fine, but the twin zeners and rectifier went a couple of years ago. Logically the zeners went 1st, so voltage control was lost, leading to burnout of the rita, which is a shame, 'cos it performed so well and is hard to replace.
Since, gone with 3-phase Boyer Powerbox and Boyer Mk4 ignition, which works well.
The lower power 3-phase alternator was only created because of the limitations of zener heat dissipation, go with the 180W and a modern reg/rect, eg boyer.
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post #12 of 14 (permalink) Old 11-15-2012, 06:41 AM
Main Motorcycle: T140 E
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Join Date: Jun 2009
Location: Reading Berks UK
Posts: 8,308
Other Motorcycle: 56 Plunger Tatty Cub
Extra Motorcycle: CZ winter bike
what the heck is a RITA magneto conversion?
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post #13 of 14 (permalink) Old 11-15-2012, 09:05 AM Thread Starter
Main Motorcycle: '74 T140V Chop
Senior Member
Join Date: Jul 2012
Location: Woodbridge, UK
Posts: 388
Out of interest, does anyone know what a boyer 3 phase power box will supply? I have a tri spark and having no battery might be nice.

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post #14 of 14 (permalink) Old 11-16-2012, 07:34 AM
Supersport 400
Main Motorcycle: Triton 650
Join Date: Nov 2012
Location: Isle of Wight, UK
Posts: 99
2 replies in one:
Back then in the early 80's, as far as I know, the only generally available after-market electronic ignitions were Lucas Rita and Boyer.
Lucas Rita had been fitted as standard to the T140 since about 1979, I think.
Both these systems were intended for replacing points in timing cover (ie unit construction) bikes.
As mine is a pre-unit T120 with magneto, I couldn't use them in that way.
Fortunately, an engineering firm called Mistral Engineering started making a housing which fitted in place of the magneto (holding the magnetic pickup), supplied as a complete kit with amplifier box, coils etc, for much less than the cost of having my duff magneto reconned.
It was a great setup, giving great service for nearly 30 years, with only the coils needing replacement once, and only met it's maker due to overvoltage when my zeners went open circuit, toasting the amplifier box.
Lucas stopped selling the amp ~10 years ago, they can be reconned (at a price) or bought used, but I didn't want to be reliant on these solutions.
So I bought a magneto replacement from Norvil (also available from Goff, Pazon etc) which is able to take to take any of the side points replacement electronic ignitions, and stuck a Boyer MK4 in it. It has worked fine for a year or so, though the mag replacement body is not as well-engineered as the Mistral/Rita unit was. I am hanging on to that old unit, as eventually Mistral will be supplying their high quality Moira amplifier, which will run off the original Rita pickup/mag body.

To loxx101's query, the 3-phase Boyer powerbox doesn't "supply" as such, it just regulates the alternator output. It is rated at 280W, which gives a generous safety margin for the Lucas higher 180W max output alternator (there is a lower ~135W Lucas 3-phase alternator also available, confusingly often listed with the same P/N).
My experience with the higher power alternator was that it produced enough power at low revs to enable a fair tickover, with no power being drawn (lights etc) other than for the electronic ignition (somewhere in the 35W ballpark), but you would need a capacitor in place of the battery to smooth the charging pulses. I believe the Lucas 2MC is the job, and is listed by Norvil.
While this got me by for some years (it's a T120 in a triton, and I didn't have anywhere to put a battery at the time) I did find night riding tedious, either having to turn the lights off at junctions, or hold the throttle at a fast idle to keep lights on.
Ultimately I glassed a battery pocket onto the front of the oiltank, and run a battery ever since.
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