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[Davedup]

Having got most of my primary side back together on my super meteor I thought I'd fit a new rotor I'd picked up (already 12V). Went to fit to discover that the one currently fitted is Lucas 54210937 and the replacement is 54202299. The new one is narrower, same diameter but not as deep. What's the difference? Are they both 12V or is one 6V? If I fit the new one then it doesn't come to the edge of the stator,. It looks like there are spacers behind the stator on the mounting ring. If I remove these can I use this new one?

[Spudgun]

Alternators are rated in Watts, not Volts. It's true that many vendors describe replacement alternators in Volts, probably because the buyers don't understand Ohms Law. Moving on...

Your rotor will quite cheerfully put out 12 Volts. However. It's probably not a match for the Stator. As it's narrower. It'll have a lower magnetic field. The upshot being (Pulling numbers out of the air): Your 100 Watt alternator will now be an 80 Watt alternator.

You should be OK.

[vince]

Hi, How wide is the alternator ? There were some narrower types produced. It maybe that that part is incorrect. Vince

[PeteF]

How much narrower is it? Does the securing bolt tighten down OK?
If it's not much different and goes on tight it will be fine.

[Davedup]

Sorry my use of the word "narrower" has caused confusion. The new rotor is the same outside diameter, the central hole is the same size and fits fine. The depth is different, the new one is around 35mm but the old one was 43mm. In other words if you laid them flat on the bench then the old one would stand up higher.
The stator is mounted on the adaptor ring but packed out with spacers. If I removed the spacers then the new rotor would fit exactly into the rotor as it is the same depth.

IMG_20201219_115554291.jpg (3.1 MiB) Viewed 2232 times

I need to make sure there's clearance for the stator without the spacers but I think so.

[Bullet Whisperer]

It can be seen clearly in your picture that the extra width of the old rotor has been doing nothing, looking at the wear marks from where it has touched the stator. There were some stators which were wider, with wider windings, which would have matched your old rotor, so your new rotor should be fine with your stator and if the magnetism happens to be stronger, due to it being new, it might improve the output slightly.

[vince]

Hi, I checked mine, there are no spacers fitted. Vince

[Davedup]

Thanks guys, will head back out to the garage.

Dave

[Spudgun]

I did a spot of digging on this (By looking at our Hosts spare part listings). It appears that the wider rotor is from an early Bullet with a 3 wire stator. There's no spacer either. The more narrow rotor is from the later Bullets with a 4 wire stator (and requiring the spacer).

Interesting.

[Davedup]

Thanks Spudgun, the wider part number also seems to correspond to a Rocket three or Trident!