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Author Topic: tap sizes  (Read 934 times)

Offline Drew Back

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tap sizes
« on: 16.03. 2015 03:22 »
Can someone tell me the correct thread size for the head bolts and rocker box bolts..It seems there are so many different thread sizes and I dont know what tap sizes to purchase..Are they the same sizes as the A10 Iron head??
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Offline duTch

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Re: tap sizes
« Reply #1 on: 16.03. 2015 06:32 »

 (Fairly sure) Head bolts are 3/8" BSF (one of the few uses of bsf on a pre-unit BSA)
 Alloy head rocket cover long bolts on mine are 5/16" BSC, all other screw ins are WW so far as I know
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Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Offline wardleybob

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Re: tap sizes
« Reply #2 on: 16.03. 2015 18:44 »
As dutch says 3/8 bsf  5/16  bsf.
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Offline muskrat

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Re: tap sizes
« Reply #3 on: 16.03. 2015 18:55 »
The r/box bolts are same for iron and alloy heads, 4 of 5/16" x 3-1/2" CEI (BSC or Cycle thread) and 1 of 1-1/2". The studs differ, iron head 4 of 5/16"-18-26 x 1-5/16" BSW/CEI, alloy head 4 of 5/16"-18-26 x 1-13/16" BSW/CEI. The front studs on the plunger are 1-7/16" long.
3/8" BSF is correct for head bolts.
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'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Offline Drew Back

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Re: tap sizes
« Reply #4 on: 17.03. 2015 14:28 »
Thank you all again for the help..
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