Author Topic: Barrel Threads  (Read 557 times)

Online Nourish

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Barrel Threads
« on: 20.02. 2026 21:30 »
Are the long stroke barrel threads definitely a standard 3/8"x 26 BSCY? I ask because I'm trying to clean out the threads and having to push down very hard with a tap to get started and it feels like I'm cutting a fresh thread!
Long stroke A7

Online berger

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Re: Barrel Threads
« Reply #1 on: 20.02. 2026 22:29 »
most probably 3/8th bsf like other barrels ,

Offline fffcycles

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Re: Barrel Threads
« Reply #2 on: 21.02. 2026 04:23 »
I used 3/8’s BSF when I did my ‘48.
Frank P Kamloops BC
1948 A7 Long Stroke, a collection of BSA D1/B44/B50/A65 from the 50's thru 70's, Ariels/Nortons/Triumphs and a smattering of Japanese

Online Swarfcut

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Re: Barrel Threads
« Reply #3 on: 21.02. 2026 08:56 »
No....Not what you expect. This is one of the exceptions to the usual BSCy/CEI thread. The four rocker box bolts on the later short stroke engine can also be a conundrum, this is how these threads into the head get cracked off.

 Use the part number and thread size chart in the Forum Literature Section to identify the thread on any unknown application and in any case proceed with caution.

 Swarfy.

Online Nourish

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Re: Barrel Threads
« Reply #4 on: 21.02. 2026 18:09 »
Thank you chaps
Long stroke A7