Alternator Nut

[courtney]

Hello,

Having a few issues with an alternator nut for a 1965 BSA C15F. I ordered a replacement nut as the one I removed was butchered. I assumed the part number I needed was 29-2023 and I ordered a replacement nut. I not able to get this nut to fit and have read in passing that the threads changed on later models. I was only able to get it on a bit, but the old nut screwed on with ease.

Is this the case and, if so, what part do I need? I was unable to find a parts fiche or a list of parts with the correct information on it. As I understand it, the C15F motor has a few changes to the earlier ones.

If anybody is able to advise I would be extremely grateful, and if you know the part number that I need  then that would also be greatly appreciated. It's driving me nuts!

A thousand thanks!

[courtney]

The fiche on the unit singles website shows it to be the part number and part that I have been delivered. Is this right?

https://www.bsaunitsingles.com/Archives/Spares/BSA%2000-5119%201965%20C15F%20Road%20x.pdf

[chaz]

interestingly, Drags have 29-2023 listed twice, no stock and no dimensions, they also have 40-0454 which is 5/8" x 20tpi.
Baxter have as 11/16 x 20.  https://www.baxtercycle.com/product/40-0454/
also 29-2023 is 9/16 x 20  https://www.baxtercycle.com/?post_type=product&s=29-2023&asp_active=1&p_asid=1&p_asp_data=1&current_page_id=31606&woo_currency=USD&qtranslate_lang=0&filters_changed=0&filters_initial=1&asp_gen%5B%5D=content&asp_gen%5B%5D=title&asp_gen%5B%5D=excerpt&customset%5B%5D=product&customset%5B%5D=avada_portfolio

think you will have to measure the diameter and tpi to double check, its not impossible they have a batch made wrong.

my lists say 29-2023 is 9/16 x 20 and 40-0454 is 11/16 x 20 all threads being BSC/CEI

chances are, that the old one fits because it has been on and off a few times!! butchered you say...forced may be another word.

[Bess]

Hi,
     Seems right, your bike having a 9/16" CEI thin nut, the other C15 option is 29-2053 5/8" CEI shouldered nut.

I can't be 100% sure as suppliers are offering unified thread nuts which are also 20 tpi, but a different thread form. The root of the UN nut is shallower, the crest higher than the CEI form, so if I am right and it's a CEI thread there will be a clash making the nut tight.

Worth having a look inside the nut to compare the crank and nut thread root.

If you are not happy try a CEI nut or run a CEI tap through.

Best wishes...

[courtney]

Hello,

Thanks both for the replies. They're both equally helpful and slightly confusing being that I've only really been used to metric in the past.

I forgot to mention in the first post that the one I ordered was listed as a 5/8 20 tpi. Feked has this listed as a unified thread. From what you both say this doesn't seem right, even though it's listed with the same part number.

I wasn't sure if the thread was cut right so I'll have a look at it properly when I get home. The engine is sitting on my kitchen work top at the moment, and even though I'm not married I'm keen to get it done.

Many thanks for your replies.

[chaz]

As mentioned on a previous thread, some suppliers are getting fasteners in "in the parish" , they say 26tpi is same for BSF and BSC, 20 tip UNF same as BSC, M5 same as 2BA.
Definately not UNF

[courtney]

Hi Chaz,

Thanks for replying.

Searching online I noticed that some alternator nuts for other bikes shared the same part number as the rear wheel nuts. I had a go with the rear wheel nut from the C15 and it threaded straight on, so I know this is the same thread, whatever that is. The wheel nut has got a shoulder, which is no good for the alternator but at least I can work out what size/type I need.

Does anybody know what size/type thread the rear wheel nut is? I've had a look online but could not find anything myself.

Thanks for your help.

[chaz]

which nut, the long or short?

29-6238   9/16 x 20   https://www.baxtercycle.com/?post_type=product&s=29-6238&asp_active=1&p_asid=1&p_asp_data=1&current_page_id=31865&woo_currency=USD&qtranslate_lang=0&filters_changed=0&filters_initial=1&asp_gen%5B%5D=content&asp_gen%5B%5D=title&asp_gen%5B%5D=excerpt&customset%5B%5D=product&customset%5B%5D=avada_portfolio

or 40-6021 https://www.baxtercycle.com/product/40-6021/  5/8x20

[courtney]

The long one. When I checked last night, 9/16 was't close to be the right size. I've confirmed with someone else that it is 5/8, as well as the link you just sent, so the nut that I got is just a duff one. The more I look at the threads on the replacement that I got at first the worse the threads look.

I've ordered a replacement from a different source, so hopefully I'll get that soon and I can compare the quality and fit.

Many thanks again for the answers, it's been very helpful.

[Bess]

Hi,
     An apology, on further investigation my fixing master list was wrong, part number 29-2023 is 5/8" 20 tpi CEI. You need this size.

If you bought your replacement from the link below, they are offering a 5/8" Unified thread, namely 20UN which is 20 tpi but wrong thread form.

https://www.feked.com/crankshaft-alternator-nut-bsa-29-2023-29-2053-21-2066.html

I guess there has been a batch pushed out to all suppliers, a number of people on this forum have had issues with being sent wrong items lately.

NOTE:

CEI is usually 26 tpi, but on larger diameters there are also 20 tpi options.
There is also a possibility the supplier has given you a CEI 26 tpi nut.
BSCy superseded CEI and dropped the BSCy 5/8" 20 tpi option so you wont get a 5/8" 20 tpi BSCy thread form (there is a subtle difference, negligible so interchangeable), so there is also a possibility you have been given a 5/8" 26 tpi BSCy.

You might find them difficult to source so running a tap through what you have will be fine. Its worth buying a tap as this will crop up again, I've had the issue a few times.

A bit muddled and hard to write down, so I hope this understandable, if not ask questions and I have another go

Best wishes...

[courtney]

Hi Bess,

That makes sense, thank you. I didn't get it from Feked but a different seller who didn't seem to want to acknowledge that there was anything wrong. I've found an alternative supplier of new nuts that seem more savvy and they have reassured me that what they supply is correct. I'll post up when I get it if it's right.

Thanks.

[Ian C]

5/8" UNF is 18 TPI with a 60 degree thread angle and this may be what is being supplied these days? In cases where I cannot easily obtain special types of nut, I make my own from hexagon stock and tap them out myself.. I buy taps and dies from a tool supplier in Mytholmroyd nr Hebden Bridge, and I've always been happy with their service. Obviously if you don't have access to a lathe then this route may prove to be difficult. It has been known in the past though, that although threads are correct TPI etc.. the plating has been thick enough to prevent the nuts screwing on to their respective shafts. In this case a tap of the correct dimension would be good to 'clean' out the plating.