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#827233 10/20/20 4:34 pm
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TriVin Offline OP
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I'm looking to upgrade the alternator on my 66 Tiger 100SS. What are the best options? RM21-23-24? The bike has been converted to 12V many years ago and a Boyer fitted by previous owners. I can ride with just a LED pilot light but full beam headlight is a no no.

Last edited by TriVin; 10/20/20 4:35 pm.

Dave
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Vincent Comet 1952
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I'm looking to upgrade the alternator on my 66 Tiger 100SS. What are the best options? RM21-23-24? The bike has been converted to 12V many years ago and a Boyer fitted by previous owners. I can ride with just a LED pilot light but full beam headlight is a no no.


Well your present charging system evidently isn’t up to scratch. There could be various reasons for this, knackered rotor primarily (lost magnetism), partially knackered stator, rectifier or zener diode, or just old wiring.

The RM24 with a 3-phase reg/rec is the best option if you ride the bike anytime day or night, or with lights on. This won’t solve any failings in the old wiring though, so that still needs to be checked.

RM21 isn't an upgrade, its the same as your RM19 with 2 wires joined for 12V. The high output RM23 single phase stator with an appropriate regulator would probably satisfy your needs, but why would you?

Luckily, Stuart’s back, so he will take you through all the monotonous business.

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BSA guy but I'll bite: I recently refreshed my alternator with a brand new rotor and an NOS single-phase Lucas stator. Wiring is all new and I'm running a Tympanium rectifier/regulator. Taillight/stop light is standard, and headlight is a sealed-beam automotive bulb (45-55W, I believe), with no pilot light. Headlight on is required at all times in NYS.

I also installed a digital voltmeter, and I've noticed that, with the headlight on, I must turn somewhere in excess of 2K rpm to bring the voltage up to 13V. Static voltage of battery is 12.7. At idle with headlight off, voltage is right around 13. At idle with headlight on, voltage is 11.7-11.9. With headlight on, voltage climbs to 14.5 somewhere around 3500 rpm.

I live in a rural area, so this setup is satisfactory to me. It also helps to have an 11 AH battery (Motobatt AGM, great battery IMO), as it can tolerate a moderate discharge for a longer period of time. Overall, the battery stays charged.

If you live in an area where you have to do a lot of idling, you may require one of the higher-output stators.


Mark Z

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all later stators (74mm) can use the same rotor .
an old stator can often benefit from a new rotor .

the RM 21 is just the older RM 19 with the
3rd wire , "12volt conversion" done inside the encapsulation .
( so 12 volt and 2 wires ) ... single phase 10.5 amps .
fine if you are running all LEDs ... or a decent battery ...
or everything is not 40 years old .

RM23 ... 12volt , single phase ... 14.5 amps ( higher output , but slower to build to full output )
... got to keep the revs up to see the benefits .


RM24 ... 14.5 amps ... higher-earlier output curve
the 3 phase output needs 3 phase rectification ...
best Lucas pattern ,
a practical solution for stop and go traffic and bikes using sprocket ratios that lower rpms .
the phasing can also have some unexpected benefits , like even starting a bike
with no battery or capacitor ... as the overlapping phasing mimics some properties of a capacitor .
( can usually run a 60 watt bulb )

the amp rating is the amp turns in the stator ... once the rotor spins ... the amps fill ...and then the volts rise .
the output wattage is determined by the amp turns ... and then , how fast the rotor is spun .
so amp ratings are independent of wattage because wattage can only be applied to an RPM .
this can cause some confusion when comparing advertised ratings . ( what you can get and when you can get it )

the 3 phase stator is-like 3 smaller stators packed inside the same volume stator .
the 3 phases are 120 degs. out and over-lap ... as opposed to 180 degrees out with no overlap .
the shorter amp phases fill more quickly allowing the voltage to also build quicker .
( wire gauge is also at play here )

there is also a lower amp , 10.5 amp RM24 pattern out there and available .
it should make its full power alittle bit lower than the 14.5 amp version .
for anyone who likes/understands the benefits of three phase ... but does not need extra power ,
( maybe running an all LED bike with no battery ? )

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On a higher revving T100 a RM23 might be ok, or even a new RM21 and rotor, but why waste money when you can get 180W from a RM24 for similar cost?
The new rotor may be the major factor.

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I prefer a 47205/16 stator with a Podtronics unit rated at 200W

That will make a strong (and reliable) system


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"I prefer a 47205/16 stator with a Podtronics unit rated at 200W

That will make a strong (and reliable) system"

Can you give reasons for your preference, otherwise your preference doesn't mean anything.

Wouldn't the 3-phase stator with an appropriate (maybe Podtronics) reg/rec also make a strong and reliable system?

There are undoubted long-term benefits with the 3-phase, at small additional cost.

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Originally Posted by C.B.S
I prefer a 47205/16 stator with a Podtronics unit rated at 200W

That will make a strong (and reliable) system

Mhm, not really CBS. Had it n my A65 and my observations are close to what Mark Z wrote. You need revs to get more juice from this stator and in average riding condition in town, with my lights constantly on, with lots of traffic and intersection with lights a few times I had to turn off my lights to get home. With the same revs it doesn't give any more power than RM21.
I use 3 phase copy of RM24 in my Trident now and still with lights on, stop light on and blinkers working its discharging battery on idling engine, but starts charging it first moment I start from traffic lights and my revs go above 1500 rpm. I have an electronic gizmo sitting in one of my idiot lamps and can see whats going on during my rides..
so koan and quinten are right about 3 phase being the best solution and cost wise it's much closer to 1 phase than it used to be.

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Results may vary, mine certainly do.
Both my '72 T120 and '72 T150 use the stock RM21. T120 has a Tympanium, T150 is completely stock. But, I must use an LED headlight on the T120 to see over 14V charging. The T150 gets there even with an H4 lamp.
My A65 always had charging difficulty on short trips in traffic until I found an RM24 unit on eBay, early '79 Triumph. Even though it's the early 10.5A version, the voltage comes up at anything above idling speed. The peak voltage might be the same, but the average total will always be more with a 3-phase.
The RM23 is an alternative, high-output single phase. However, it was first seen on Mk3 Commandos and used twin Zeners to deal with the increased output. You must use a 200W regulator.
Given that you must replace the regulator anyway, and from what I see the 3-phase stator is no more expensive, I really see no reason to not go with the RM24.


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Hi Dave,

Originally Posted by TriVin
I'm looking to upgrade the alternator on my 66 Tiger 100SS. What are the best options? RM21-23-24? The bike has been converted to 12V
Originally Posted by koan58
RM23
RM21
why waste money when you can get 180W from a RM24 for similar cost?
+1. I've used the high-output versions of the RM24 since the early 1980's on my T160's; even when I had to plod across pre-M25 London on a Friday evening, electric-start would always work when required.

Same as @koan58, I see replacement stator costs are similar irrespective of power output, so the high-output RM24 is "the most bang for your buck". thumbsup As you're also in GB, afaik currently the cheapest is TMS, I always pay the small extra charge for the "UK MADE" - scroll down the webpage 'til you see "47244/UK" in the left-hand "Code" column.

Not mentioned so far in this thread is you'll need a reg./rec. to replace the separate rectifier and Zener diode:-

. Cheapest is https://www.eBay.co.uk/itm/NEW-5-PIN-Voltage-Regulator-RectifIer-for-HONDA-CBR600-900RR/292226480932 plus https://www.eBay.co.uk/itm/HONDA-TY...ONNECTOR-REPAIR-PLUG-SOCKET/174253997810 - btw, risking telling you something you know already, BritBike has a bug that means just clicking on those links in my post won't work, you have to "Quote" my post then copy a link from the quoted text into a new browser tab. thumbsdown In case you're wondering, despite their low cost, these are reliable, @NickL has been recommending them for about a decade without any posted problems.

. If you want to pay more for GB-based backup, A Reg 3 from Al Osborn or Podtronics from TMS ("VR.10124/P" in the "Code" column at the bottom of the webpage linked above).

. Any of the above are easy to connect into your bike's electrics:-

.. Red wire to the battery +ve terminal, Black or Honda Green wire to the loom Brown/White off the rectifier (so the Ammeter continues to work as normal), Yellow wires to the stator wires.

.. Disconnect and tape up the wire connected to the Zener's 3/8"-wide spade terminal.

Originally Posted by quinten
the RM 21 is just the older RM 19 with the
3rd wire , "12volt conversion" done inside the encapsulation .
( so 12 volt and 2 wires ) ...
RM23 ... 12volt , single phase
Regrettably, neither of these statements are correct ...

Alternators produce AC and their AC Volts vary a lot with both rotor rpm and load across the stator. Otoh, "12volt" is a nominal DC system Voltage; the alternator AC Volts must be regulated to that, hence connection to a reg./rec. or Zener diode(s) ... if you so wished, nothing to stop you connecting a RM21 or RM23 to a '6volt' reg./rec.

The RM21 generates more than any RM19 version supplied for these old heaps. However, not much more and given a new one's pretty-much the same cost as a new high-output RM24 stator, which does generate much more at both high and low rpm ... thumbsup

Originally Posted by koan58
RM23 might be ok,
The "RM23" designation has been confused by Wassell:- frown

. When 'original Lucas' made them, as @quinten half-posted, they were rated for 14.5A @ 5,000 rpm, same as the high-output RM24 stator, RM23 just generated a bit less at 2,400 rpm (the other rating 'original Lucas' advertised).

. Otoh, Wassell now claim "16A" for their "RM23"; however, they've consistently failed to produce a rpm/Amps curve for this alleged enhanced output and, as @Adam M. posted, he didn't see any increased output at lower rpm ...

Originally Posted by quinten
there is also a lower amp , 10.5 amp RM24 pattern out there and available .
it should make its full power alittle bit lower than the 14.5 amp version
Otoh, in real life, 'original Lucas' quoted "10.5amp" @ 5,000 rpm, same as they did for every other stator they supplied to motorcycle makers ...

Hth.

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TMS have either run out or very close to doing so of the UK made alternator stators. Get in fast, and if they have none then you will need to trawl around a lot to find one.

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Thank you everyone. That has sorted that out.


Dave
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Vincent Comet 1952
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Originally Posted by Stuart
As you're also in GB, afaik currently the cheapest is TMS, I always pay the small extra charge for the "UK MADE" - scroll down the webpage 'til you see "47244/UK" in the left-hand "Code" column.


interesting. The one on my Lightning is British made one, although the one I’ve bought for the Thunderbolt is one of the new wassel Lucas ones (there’s me saying the other day I’d not buy anything wassel eek )

Are the wassel ones particularly bad?


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We will see, I bought one 3 phase for my bitsa too.
For now Don in different thread is complaining about a new Wassel stator melting after 600 miles of use and looking for a cause in Tympanium regulator, I'm afraid it could be stator problem. Feel worse at once about not looking for Made in England stator which I have in my Trident and working flawlessly for a long time.

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I have the RM24 and new Lucas rotor. I was riding by night (very cold one at 4AM) in high gear of course with lights (low beam -Lucas lamp-) and heated gloves switched on the battery. Long 400km riding but I needed to disengage the gloves cause I almost ran out of energy to have the lights ON and most important; keep in riding. Then after 1200km on that same trip, the battery was almost dead so I bought a new one to ride safe home. The older battery I connected it to the charger and came alive but discharged very soon; so killed the battery.

What I am trying to say is that the RM24 is not enough if you need more than couple of minimum lights and the EI
Seems that there is a powerful version but I am not sure if actually works better or is just marketing.

May be any of you have one of those?

Thanks


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