Author Topic: Bore size a10  (Read 3160 times)

Offline erik

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Bore size a10
« on: 18.12. 2012 07:45 »
Hello!

I've just got my first bike back, after 17 years, but it's in a poor state and is in nead of a lot of work.
It's fitted with 71mm pistons, but the barrels is rusty and need quite a big bore.
What is the max bore this barrels can take?
The alternative is of course a new set of barrels. Anybody know where I can get that?

Erik, Norway

Offline renos-a10

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Re: Bore size a10
« Reply #1 on: 18.12. 2012 08:03 »
Hi Erik

 You can fit piston 71.5mm. The piston 71mm is +0.40 so you can fit 71.5mm ( +0.60 ).

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1954 BSA A10 Plunger
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Offline mark

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Re: Bore size a10
« Reply #2 on: 18.12. 2012 08:36 »
Erik,  I am running +80 without any problems.

Mark
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Offline Rocket Racer

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Re: Bore size a10
« Reply #3 on: 18.12. 2012 08:43 »
As long as it hasnt been resleeved, they will stand +100 or 72.5mm,
 however once resleeved the strength isnt there and I recall + 60 the limit, before sleeves need replacing.
If the fins are intact sounds like its got years of service left.
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.
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Online muskrat

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Re: Bore size a10
« Reply #4 on: 18.12. 2012 09:34 »
 G'day Erik, welcome to the forum.
                                              I agree with RR. I have just put +40's (71mm) in a set of re-sleeved barrels and looks to be able to go at least +70 or 80.
I have a set of Mondial +70 on the shelf that I would feel comfortable with in my re-sleeved barrels.
 Ask your borer (machinist, Mechanic) how much he thinks it would need to go out to clean up and hunt for pistons that size or 1 bigger.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline erik

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Re: Bore size a10
« Reply #5 on: 18.12. 2012 13:33 »
Thanks a lot guys! I´m afraid it is so rusty it need to take of too much, but hey, shame on those who doesn´t  try! The biggest I´ve seen on ebay is +60 (71,5mm), but maybe I should be lookin´ for +80.

Offline mark

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Re: Bore size a10
« Reply #6 on: 18.12. 2012 20:41 »
Cake St Classics in the UK have Wiseco pistons in + 80.

Mark
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Online KiwiGF

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Re: Bore size a10
« Reply #7 on: 19.12. 2012 00:16 »
Hi all,

I just thought it might be worth sharing some advice I was given from a trusted engine specialist regarding my A10's sleeved barrel.

Basically the guy reckoned I should not allow the sleeve to be bored such that the resultant wall thickness is less than 1 mm, as going thinner than 1 mm is not worth the risk of the sleeve cracking and/or the sleeve moving in the barrel. Basically it's one of those "it might be ok but...." type decisions.

In my case the sleeves are (as near as I can tell) 1.5 mm thick wall and it's on std (nominal) bore of 70.00mm. So the barrel must have been bored to around 73mm to accept them, which is the equivalent of +120 thou oversize.

If I took the advice of the specialist I could theoretically bore the sleeves (twice) to 71 mm and keep to the 1 mm wall thickness recommendation, 71mm is +040.

Hopefully I will never have to decide whether to bore the sleeves to +040, or even +020! Along the same lines I hope to never find out how feasible it is to reline a barrel that has been relined before.....

I've not had any advice on "when" to re-sleeve instead of bore to the next size but I guess it's another "it might be ok but...." decisions based around whether the A10 barrel will become more prone to failing with (say) +100" pistons fitted, than if a liner was fitted - the theory being a liner will add to the strength of the barrel, particularly the stubs, and +100 bore will make the stubs quite a bit weaker than standard.
 
Here's some figures, remembering these sizes are "nominal" and bores are usually made to suit the brand (and exact size) of a given piston.

Bore/dia Nominal Size
70.00   Std bore size for an A10
70.50   +020"
71.00   +040"
71.50   +060"
72.00   +080"
72.50   +100"
73.00   +120"    
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Offline duTch

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Re: Bore size a10
« Reply #8 on: 19.12. 2012 09:57 »


Hiya Erik,
               Check out post by MJ (?) re new  A10 barrels???/Norvin  Mike Pipe +44 2088 015659
If I can find it will post, unaware of quality, am sure they're ok as  affiliated with vincent racing(?) but am seriously thinking about some for me as a backup.
 They advertise in  maybe Classic... Racer?
 Cheers and welcome,
 duTch
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Re: Bore size a10
« Reply #9 on: 19.12. 2012 11:10 »
 Is this the one Dutch  http://www.a7a10.net/forum/index.php/topic,5915.0.html
I'd have to find a busier corner for the missus to work  *eek* to afford them. *smile*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline duTch

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Re: Bore size a10
« Reply #10 on: 20.12. 2012 13:19 »

 Yup Muskie,That's it thanks, I'm keen for some as backup, and don't have a missus to send to corners(got a beeza *eek*),
 Be good to get some feed back on them first, but if not will do any way, but also need a crank, and may as well chase up cases to fit em all and have a spare bottom ready to go.
 cheers and steer clear of bahbah humbugs (bedbugs in ugh boots?), duTch

Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Rocket Racer

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Re: Bore size a10
« Reply #11 on: 23.12. 2012 03:55 »
Is this the one Dutch  http://www.a7a10.net/forum/index.php/topic,5915.0.html


A good mate who has been into vincents for many years warned me about dealings with that crowd, was enough to sound warning bells.
caveat emptor
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Offline pato08

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Re: Bore size a10
« Reply #12 on: 10.01. 2013 19:14 »
 Just hi-jacking this thread, will these barrel sleeves suit my 1957 A10 plunger ?
Ebay # 140774834601

Thanks Pato
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Online BSA_54A10

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Re: Bore size a10
« Reply #13 on: 11.01. 2013 05:12 »
Please when you post an evilbay link copy & paste the entire addresss as there are members here from all over the world and logging into evil bay in another country can be a bit of a PIA.
Use the web link button just above the smilies ( 2nd button with the globe & page on it ).

I sleeved a few bike reciently and found that standard & +20 pistons are alot easier to get and cheaper to boot.
Bike Beesa
Trevor