B50 rotor nut.

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midgie
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B50 rotor nut.

Post by midgie »

Be sure that the thread on the crank is 5/8" x 18 TPI as it says in the parts book, as some I have found are 5/8" x 20 cycle thread, just a heads up before you try to wind on the wrong nut!
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kommando
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Re: B50 rotor nut.

Post by kommando »

The 20 TPI is the pre OIF rotor nut, so either dropped into the wrong box or a supplier assuming they were the same.
midgie
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Re: B50 rotor nut.

Post by midgie »

kommando wrote: Wed Jan 22, 2020 5:25 pm The 20 TPI is the pre OIF rotor nut, so either dropped into the wrong box or a supplier assuming they were the same.
No the thread on the crank is 20tpi.
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chobbler
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Re: B50 rotor nut.

Post by chobbler »

Midgie's right. I've got one of these 20 tpi cycle thread cranks on my B50. The nut is larger, flat with no shoulder. I can't make the standard lockwasher work without a shoulder nut, but the shoulder nuts only come in 18tpi.
Somebody on here said the Norton lockwasher works. I note the Norton uses 20tpi and nut has the shoulder. I wonder if I can use the Norton bits?
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Re: B50 rotor nut.

Post by Jeff K »

I have used a Norton rotor Nut on a B40 Crank. It was a NOS later B40 Crank the I got from Peter Quick. I tossed the 1961 6v rotor and stator and upgraded to a 1970 B25 12v rotor and stator. The later stator was thicker and the B40 nut seemed too short. The Norton nut was a little long so I turned it down to fit. Threads were correct to fit.
I thought all B50 were OIF? So shouldn't all of the cranks be the same?
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Re: B50 rotor nut.

Post by midgie »

I have b50 cranks here that are 5/8 x 20 tpi and 5/8 x 18 tpi . The parts book list's the nut as 5/8 unf but not all are!
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chobbler
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Re: B50 rotor nut.

Post by chobbler »

I came to the conclusion that they weren't all made in-house.
I would like to know who made what parts for BSA, especially in the last few years to collapse.
Has anybody documented it anywhere?
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Re: B50 rotor nut.

Post by Jeff K »

I wonder when the two threads where made? one early and one late? With the BSA factory shut down and the last few B50 being rebadged and sold as Triumph's, I could see them running out of parts and having some "out sourced"
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Re: B50 rotor nut.

Post by chobbler »

I just changed my rotor today because the old one seems to have lost its magnetism with age :uhu

Is there a way to torque it back up without having to take the clutch cover off and lock it? My clutch is just right at the moment so I don't really want to disturb it.
I used an impact gun to get nut off, and have put it back with a very quick "thrap" of the same, with the back brake locked up. With thread lock and new tab washer bent in will that do, or is it strictly 60 ft pounds or she'll let go?

I wasn't happy wedging a stick between the primary chain wheels and not sure I want to try the nylon cord down the plug hole trick. >44
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Re: B50 rotor nut.

Post by kommando »

Stick it in 4th and put a heavy boot on a heavy persons foot on the rear brake lever, some blue/green loctite but not red is good insurance.
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