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aftyer market alternator
#442623 07/01/12 12:09 am
Joined: Mar 2006
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58a10 Offline OP
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got the proverbial "good deal" on an aftermarket high output alternator. 75 bucks, new in the box.
im just going to install it, but i noticed straightaway that the rotor is 3/8" wider than the stock Lucas unit.
i apologize for getting ahead of myself, but remembering that the spacer between the motor sprocket is about the same width,
maybe eliminating the spacer and butting the rotor up against the sprocket?.......
the o.d. of the rotor is the same, and would fit neatly inside the sprocket concavity
here is a link to the unit

12V Lucas ALTERNATOR TRIUMPH NORTON BSA MAGNETO SPARX

it is manufactured by sparks i believe. i usually prefer name parts, but the 100 dollars off price got the better of my judgement. (shame on you, Newcastle breweries)
(link didnt work. type into eBay, 12V Lucas ALTERNATOR TRIUMPH NORTON BSA MAGNETO SPARX
)

Last edited by 58a10; 07/01/12 12:30 am.

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Re: aftyer market alternator
58a10 #442641 07/01/12 3:49 am
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My $0.02

You may want to use shim(s) to make up any centering difference. I'm taking for granted here that a rotor sits in the center (equal distance on each side) of the magneto.

I did a check on eBay for this and found it's only compatible with just a couple of Triumphs (1975 Bonny's). I hope yours is one of them. BTW - nothing mentioned about "high-output". Looks like a standard replacement.

eBay: Item #251064709892

Last edited by Ken Holby; 07/01/12 3:50 am.

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Re: aftyer market alternator
58a10 #442667 07/01/12 9:33 am
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Hi,

I hope I'm not raining on the parade here ...

. Entering "12V Lucas ALTERNATOR TRIUMPH NORTON BSA MAGNETO SPARX" into the eBay search box got me to this one.

. That is not a "high output" alternator by the definition usually used on this forum's Boards - 14.5A @ 5,000 rpm (aka '180 Watts'), Lucas RM23 (single-phase) or RM24 (3-phase) or patterns.

. Neither is it a replica of a Lucas RM21 - that was a two-wire single-phase alternator that produced only 10.5A @ 5,000 rpm (aka '120 Watts').

. More importantly, the RM21 and all subsequent Lucas stators, and the patterns, embed the coils in a greeny-coloured resin, to protect the thin coil wires from vibration. So it will not be a "replacement for the unreliable "Prince of Darkness" items"; that "replacement" is likely to be far more unreliable than the perfectly-reliable Lucas RM21 and later stators.

. It would appear to be a pattern of a Lucas RM19 or RM20 alternator; as with those, you connect two of the three wires together to give 12V, otherwise it only produces 6V and needs the specific wiring and rotary light switch to switch the stator coils.

. Lucas supplied the RM19 and RM20 from the early to late 1960's. If it's a copy of the RM20, it does indeed have a 'higher' output than the more-common RM19 but still no more than the 10.5A @ 5,000 rpm (aka '120 Watts') of the standard encapsulated two-wire single-phase RM21 that superseded it. If it's a copy of the RM19, it'll have a much lower output. frown

Originally Posted by 58a10
got the proverbial "good deal"

Alternatively, "if it's too good to be true, it probably is"?

Hth.

Regards,

Re: aftyer market alternator
Stuart #442684 07/01/12 12:14 pm
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Originally Posted by Stuart
Alternatively, "if it's too good to be true, it probably is"?


Looks like a pattern Royal Enfield India Bullet alternator, probably the same type as this one.

http://www.eBay.co.uk/itm/ROYAL-ENF...Motorcycle_Parts&hash=item3cb2882ca8

Re: aftyer market alternator
58a10 #442706 07/01/12 3:11 pm
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thanks for the input folks.
i said high output, when i meant 3 phase.
this will be going on a little little chopper thing im building. it will be running without a battery, with a dual coil, a tympanium and capacitor. the only extra loads will be lights and tail light. the out put has to be higher than the one i replaced, as it would barely light a lightbulb used as a makeshift tester. ill post again after i install it later today.
electrics have never been my strong suit, but i have learned to " not let the smoke out of the wires"


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Re: aftyer market alternator
58a10 #442712 07/01/12 4:27 pm
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That alternator if its the one you bought is not 3 phase, a 3 phase alternator has 9 coils not 6.

Re: aftyer market alternator
58a10 #442716 07/01/12 5:08 pm
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Originally Posted by 58a10
i said high output, when i meant 3 phase.

the out put has to be higher than the one i replaced, as it would barely light a lightbulb used as a makeshift tester.


That wouldn't be surprising if you had a three-wire alternator connected to run as as a 12V three-phase unit?

Three wires doesn't necessarily mean it's three-phase, and that stator will require two wires to be joined together before it would operate at 12V. It even says so in the seller's description:

"THIS ALTERNATOR WILL REPLACE ALL LUCAS 2 WIRE ALTERNATORS AS WELL. SIMPLY CONNECT THE PURPLE AND GREEN OUTPUT WIRES TOGETHER FOR BIKES WITH ZENERS OR ELECTRONIC REGULATORS. GREAT TO UPGRADE FROM 6V TO 12V.

Re: aftyer market alternator
58a10 #442735 07/01/12 6:23 pm
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Hi,

Originally Posted by 58a10
the out put has to be higher than the one i replaced,

Not necessarily. frown As you say, "electrics have never been my strong suit" so how do you know the original alternator was responsible for "barely light a lightbulb"?

Originally Posted by 58a10
it will be running without a battery, with a dual coil, a tympanium and capacitor. the only extra loads will be lights and tail light.

So? If the new alternator isn't producing much when the engine's revving, it's going to be producing five-tenths of b*gger-all at around-town revs. Why do you suppose bike makers fitted batteries? wink

Regards,

Re: aftyer market alternator
58a10 #442852 07/02/12 2:22 pm
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If you have counted the poles to see which type stator you have and it turns out to be the normal type then the new rotor will still make an improvement compared to the ancient rotor you probably have fitted. Should run fine without a battery if you have a capacitor. Make sure the capacitor is of recent manufacture. Just switch the lights off to start the bike
Dave


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