Author Topic: BSA B33  (Read 318 times)

Offline Guy Wilson

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BSA B33
« on: 11.09. 2020 15:33 »
I have a B33 plunger (1952/3 - not 100% sure. The barrel bore is 88mm. Could anyone tell me how much oversize that is from the standard 85mm bore? Is it +60 thou to mix measures...
Feked list Bore Size: 3+3/8" (85mm) Standard, also available as +.020, +.040, +.060 oversize - please select.
thank you
Guy
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Offline RDfella

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Re: BSA B33
« Reply #1 on: 11.09. 2020 16:06 »
.060" is roughly 1.5mm so .060" oversize would take you to 86.5mm Your bore is 3mm oversize or roughly 1/8"
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Online KiwiGF

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Re: BSA B33
« Reply #2 on: 11.09. 2020 21:31 »
I have a B33 plunger (1952/3 - not 100% sure. The barrel bore is 88mm. Could anyone tell me how much oversize that is from the standard 85mm bore? Is it +60 thou to mix measures...
Feked list Bore Size: 3+3/8" (85mm) Standard, also available as +.020, +.040, +.060 oversize - please select.
thank you
Guy

If its 88mm it may have been bored out for a liner? Which is not yet fitted?
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Offline Guy Wilson

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Re: BSA B33
« Reply #3 on: 12.09. 2020 06:42 »
Thanks RD, Kiwi, I doubt it was bored out to fit a liner, It came in bits and all goes together except for the piston and barrel. I suspect it may have had VW piston in a some point (the 1600 engine) was an 88mm bore.. I shall investigate more now I know its not a BSA oversize,
All the best
Guy
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Offline Guy Wilson

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Re: BSA B33
« Reply #4 on: 12.09. 2020 07:34 »
Question: the bore on the B33 barrel is 88.3 or .4mm ...what would the appropriate diameter of a piston be to fit this bore? what are the tolerances?
Guy
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Online muskrat

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Re: BSA B33
« Reply #5 on: 12.09. 2020 09:54 »
G'day Guy.
At that size I'd give it 0.004" = 0.1 mm but depends on the piston type (cast/forged). I can't find any BSA/Triumph/Norton pistons that size.
I know a fella put a Dihatsu piston in a Yamaha. Lots of things need to line up. Crown height, pin diameter, skirt length etc.
Would certainly be easier to throw a sleeve in it.
Cheers
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Offline Guy Wilson

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Re: BSA B33
« Reply #6 on: 12.09. 2020 14:26 »
I agree, sleeving is the easiest.. may go that way... Guy
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Online chaterlea25

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Re: BSA B33
« Reply #7 on: 13.09. 2020 16:17 »
Hi Guy,
An available liner that is cheap and will do the job is one from a Ferguson 35
4 cylinder diesel engine . I got one for about €15  *smile*
I turned down the bottom end of the liner and stepped the cylinder bore to suit as  additional security

John
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Offline Guy Wilson

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Re: BSA B33
« Reply #8 on: 14.09. 2020 05:10 »
Thanks John, there are certainly enough tractors here.. I have a look around
Guy
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Offline Rocket Racer

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Re: BSA B33
« Reply #9 on: 28.09. 2020 01:37 »
After sleeving it back to standard, make sure you look for a long rod piston. the later BB series changed the rod length and the gudgeon pins moved accordingly, so you'll need the right piston to suit your rod type which if early (ZB?) should be the long rod.

Have owned my ZB33 since the mid 1980's, it will the last bike I'd ever sell.

IMHO avoid JP pistons for these, they grow too much and seize. try and find a hepolite or equivelent, preferably flat top
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A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline Guy Wilson

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Re: BSA B33
« Reply #10 on: 28.09. 2020 09:27 »
Thanks RR, I have a standard piston which I'll check to see if its correct for the rod. Good advice,
I've just had an enjoyable weekend on a sort of socially distanced DGR https://advrider.com/f/threads/kenyas-kinda-dgr-just-our-cup-o-tea.1469171/ Here's Hunter's write up. Many up and down hills and at altitude..
Guy
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Offline Rocket Racer

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Re: BSA B33
« Reply #11 on: 28.09. 2020 20:42 »
Thanks RR, I have a standard piston which I'll check to see if its correct for the rod. Good advice,
I've just had an enjoyable weekend on a sort of socially distanced DGR https://advrider.com/f/threads/kenyas-kinda-dgr-just-our-cup-o-tea.1469171/ Here's Hunter's write up. Many up and down hills and at altitude..
Guy
enjoyed the link, thankyou .
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A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand