Early Parts in a MK3?

Morning Chaps,

I'm just sorting/checking the collection of primary chaincase parts before re-installing them in my MK3, and I've noticed the Stator and Rotor do not have the part numbers listed in the factory manual and on the Andover site?

According to the manual the Stator should be part no. 47239 (RM23). I have part no. 47205A (RM21).

The rotor should be part number 54202299. I have 54215824.

Both these parts appear to be from earlier models, so I'm wondering if they would work on the electric start MK3, or do they need to be replaced. (Both expensive parts)!

the bike will have a Crane coil and a Tri-Spark ignition, a 4-brush starter and heavy battery cables.

The stator is lower output

LU47205 Lucas RM21
Single Phase Stator
2 lead 10 amp
LU47239 Lucas RM23
Single Phase Stator
2 lead
(High Output) 16 amp

The rotor will not need changing unless its showing signs of coming apart but the MK3 voltage regulation needs to be in place to cope with the higher output stator. So you should have 2 Zener diodes in place and connected.

Bilko said:

The rotor should be part number 54202299. I have 54215824.

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54202298/9 is the latest "welded" (it isn't actually welded) rotor neither is it an "RM20" rotor as Lucas (Wassell) insists on describing it as it's the RM21 and later (RM23, etc.) rotor. The actual RM20 rotor was wider but the RM21 rotor replaces it.

The rotor used during Mk3 production is more likely to have been 54201143 and is the rotor my Mk3 has.

The RM21stator only needs one Zener diode. (Or none if it has a modern reg/rec.)

Bilko said:

Both these parts appear to be from earlier models, so I'm wondering if they would work on the electric start MK3, or do they need to be replaced. (Both expensive parts)!

Click to expand...

They don't exactly "need" to be replaced but as kommando says, the RM21 is lower output.
"54215824" could be an ET (Energy Transfer) rotor. Are there three dowel holes on the inside face by any chance?

L.A.B. said:

54202298/9 is the latest "welded" (it isn't actually welded) rotor neither is it an "RM20" rotor as Lucas (Wassell) insists on describing it as it's the RM21 and later (RM23, etc.) rotor. The actual RM20 rotor was wider but the RM21 rotor replaces it.

The rotor used during Mk3 production is more likely to have been 54201143 and is the rotor my Mk3 has.

Lucas RM23 Alternator | Norton Owners Club

www.nortonownersclub.org

The RM21stator only needs one Zener diode. (Or none if it has a modern reg/rec.)


They don't exactly "need" to be replaced but as kommando says, the RM21 is lower output.
"54215824" could be an ET (Energy Transfer) rotor. Are there three dowel holes on the inside face by any chance?

Click to expand...

Thanks for the help guys,Yes it does, marked 'S' 'M' and 'R'

YukoNorton said:

another question about early parts on a Commando...

On my '74 850, the non-standard rear wheel has no cush drive (not changing it) , so,
can I fit an earlier Dominator or Manx clutch hub center with the cush drive with the original Commando clutch basket?
If not, what would it take to have a cush drive in the clutch hub?

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Might be a good idea to start a new thread with your question, otherwise it's gonna get confusing...

Bilko said:

Thanks for the help guys,Yes it does, marked 'S' 'M' and 'R'

Click to expand...

Assuming that the magnets are good and the center is not loose, that rotor will work fine in your bike. It is for and Energy Transfer ignition. The holes are to time the rotor to the crank as ET ignitions are not DC (no battery, Zener, or regulator) and must fire when the AC voltage is high from the stator. Otherwise, it is just a standard rotor. It most likely came from a Triumph T100c or T120C prior to 1967 or possibly a BSA B50MX other such generally off-road/dual-purpose bikes. The really early ET rotors did not have the timing marks on the front - a degree wheel was required for timing.