Three phase alternator for mk3

I have a charging issue and I have traced the issue back to a stator that is not producing a charge. I am looking to change to three phase as I use the electric start daily. Is there a noticeable charging difference between the two different output RM24 alternators?

Outside of wiring, is this a bolt on or do I need to alter the bracket? Any downside to the higher output?

maaseyracer said:

I have a charging issue and I have traced the issue back to a stator that is not producing a charge. I am looking to change to three phase as I use the electric start daily. Is there a noticeable charging difference between the two different output RM24 alternators?

Outside of wiring, is this a bolt on or do I need to alter the bracket? Any downside to the higher output?

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There are two Lucas RM24 3-phase stators available. 10.5 amps and 14.5 amps. The 10.5 amp provides the same basic capability as the single-phase 10 amp, but provides it at a lower RPM. To answer the rest of your questions requires knowing about the rest of your charging system, the bike you have (MK3 or pre-MK3), and the equipment on the bike. If you have no extra or non-stock equipment on your bike, then 10-10.5 amps is plenty. If you have LED bulbs the 14.5 is not a great idea.

Assuming a worrking charging system, the battery is more important. What battery type and size do you have?

marshg246 said:

There are two Lucas RM24 3-phase stators available. 10.5 amps and 14.5 amps. The 10.5 amp provides the same basic capability as the single-phase 10 amp, but provides it at a lower RPM. To answer the rest of your questions requires knowing about the rest of your charging system, the bike you have (MK3 or pre-MK3), and the equipment on the bike. If you have no extra or non-stock equipment on your bike, then 10-10.5 amps is plenty. If you have LED bulbs the 14.5 is not a great idea.

Assuming a worrking charging system, the battery is more important. What battery type and size do you have?

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I have a 75 MK3, Dyno Dave starter, stock lights, and pazon ignition. I avoid riding at night as much as I can. Not sure I care about LED bulbs for now. though I picked one up for my Triumph to try it out. Looking into getting a Shindengen regulator/rectifier and plan on removing the assimilator and zener diodes. Battery is the largest AGM battery I could fit in the stock location, brand is Motobat.

Why id the 14.5 amp not a good idea if you run LEDs? Does it over charge? Does it run too hot if not drawn?

maaseyracer said:

I have a 75 MK3, Dyno Dave starter, stock lights, and pazon ignition. I avoid riding at night as much as I can. Not sure I care about LED bulbs for now. though I picked one up for my Triumph to try it out. Looking into getting a Shindengen regulator/rectifier and plan on removing the assimilator and zener diodes. Battery is the largest AGM battery I could fit in the stock location, brand is Motobat.

Why id the 14.5 amp not a good idea if you run LEDs? Does it over charge? Does it run too hot if not drawn?

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No to overcharge.

Possibly to running hot.

If the power is not used, it must go somewhere and a standard bike will not use 10 amps much less 10 amps when the various bulbs draw almost nothing. Also, 3-phase is not usable with a standard MK3 charging system. A three-phase regulator is required. I use the Tri-Spark MOSFET regulator and have no specific knowledge of the Shindengen devices. As long as the one you choose is designed for 3-phase and can be connected as positive ground (should be) it should be fine.

Starting a bike with a big AGM battery in good shape does draw the battery down a little, but unless you're starting every few minutes, there's no issue - the standard charging system will work fine to bring the battery up to full charge quickly. If the bike is hard to start then that needs to be fixed but otherwise no issue.

The best thing about a 3-phase system is that it will help when you are doing what you should not be doing - riding around at low RPM. They are more efficient at lower RPMs than single phase assuming that the regulator allows the efficiency.

One more thing... The MK3 uses half-wave rectification and two Zener diodes. The pre-MK3s use full-wave rectification and one Zener. IMHO, it is a good idea to replace the charging system on a MK3 but it doesn't make a lot of difference if it is replaced with a modern single- or three-phase system. Without getting too deep, half-wave is half of full-wave.

marshg246 said:

I use the Tri-Spark MOSFET regulator and have no specific knowledge of the Shindengen devices.

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The Trispark appears to be a clone of an older model Shindengen.

maaseyracer said:

The Trispark appears to be a clone of an older model Shindengen.

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What "older model Shindengen"?

May be FH (012,014,020 MOSFET) vs SH775 (series) ?

maaseyracer said:

I have a 75 MK3, Dyno Dave starter, stock lights, and pazon ignition. I avoid riding at night as much as I can. Not sure I care about LED bulbs for now. though I picked one up for my Triumph to try it out. Looking into getting a Shindengen regulator/rectifier and plan on removing the assimilator and zener diodes. Battery is the largest AGM battery I could fit in the stock location, brand is Motobat.

Why id the 14.5 amp not a good idea if you run LEDs? Does it over charge? Does it run too hot if not drawn?

Click to expand...

I have a 76 MK 111 , Dyno Dave starter , LED lights Boyer MK 1V ignition . I avoid riding at night as much as I can . That said , I now leave all lights on all the time . A modern voltage regulator / rectifier unit . Podtronics , out in the air flow . Zener diodes are gone . Battery is Eliminator from Canadian Tire now . Batterys die or get sick eventually . Size of battery unimportant with the wonderful D. D . motor . Big cables for the Amp. draw .

As above and use and use RM23 with no issues, the BSM even indicates green at night with full beam on. The latest Wassel / Lucas stator will not fit inside a MK3 chaincase, so there's your answer.

The latest wassel/lucas stators will fit into the Mk3 chaincase but you have to reduce the OD of the boss the stator studs screw into on part No 06.4708 ( the recess in the potting compound of the new stators is smaller than the original stators)

dobba99 said:

The latest wassel/lucas stators will fit into the Mk3 chaincase but you have to reduce the OD of the boss the stator studs screw into on part No 06.4708 ( the recess in the potting compound of the new stators is smaller than the original stators)

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I am confused, how do you rectify this? Do you have to trim the recess deeper in the outrigger?

maaseyracer said:

I am confused, how do you rectify this? Do you have to trim the recess deeper in the outrigger?

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Before and after photos of the modified carrier

That's a new one on me, I only thuoght the 3 phase version would not fit. Now off to check.

dobba99 said:

Before and after photos of the modified carrier

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Thank you!

maaseyracer said:

I have a 75 MK3, Dyno Dave starter, stock lights, and pazon ignition. I avoid riding at night as much as I can. Not sure I care about LED bulbs for now. though I picked one up for my Triumph to try it out. Looking into getting a Shindengen regulator/rectifier and plan on removing the assimilator and zener diodes. Battery is the largest AGM battery I could fit in the stock location, brand is Motobat.

Why id the 14.5 amp not a good idea if you run LEDs? Does it over charge? Does it run too hot if not drawn?

Click to expand...

I would think twice about removing the assimilator if it is a Canadian model. Canada requires daytime headlight after 1974 (as the US does too now) and the Canadian assimilator feeds the lights from the alternator-only in the one of the ignition on-positions. In that position the lights couldn't run the battery down at idle because the lights aren't connected to the battery in that position.

Also, the MKIII charging does use full-wave rectification but it's not obvious from the wiring diagram. The two zener diodes are the other half of the full-wave rectifier and serve as the voltage regulator. Being mounted in the "Z" plates they have a nearly infinite heat sink. Twenty-odd years ago I installed a three-phase system that included a new rotor, stator, rectifier and new zeners. After that the battery would stay up despite my commuting in heavy traffic with the lights on. Had I understood the function of the Canadian assimilator at the time, I probably could have replaced just that and solved the problem. In any case it has worked flawlessly ever since getting the 3-phase electrics.

I had the same trouble with my R100 BMW in heavy traffic and attempted to rig something similar on the Bosch system. The parasitic load of the alternator field (about 4 amps) reduced usable output at idle to below lighting/ignition draw. I soon discovered a Saprisa alternator for Ducati/Moto Guzzi that was a bolt on and used that. Problem solved. The saprisa is a permanent-magnet setup like the Lucas with no parasitic loss to the field coils.

Late to the discussion here but a 3 phase stator bolted in my MK3 with no modification. I still have incandescent lamps including a halogen headlamp that stays on while riding. I do shut it off if at an exceptionally long traffic light. DD starter, very heavy starter cables - aircraft wire that I had on hand years ago trying to get the most out of the original starter. Largest AGM battery that fits is about 5 years old now and probably on its last legs. I notice the LED voltage indicator that I installed in the charge hole goes from green to red fairly quick now at idle.