The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: ctjanney on 09.11. 2025 21:13
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Hello folks. I have, according to the block and frame number, a 1955 A7 Shooting Star, but here are questions. The rear brake is not the normal A7 push rod brake, but the cable brake, with the cable on the right side as in the more '60s A65 frames. And even though the block number is CA7 SS 742, there are 8 fines on the cylinders, and not the 7 I would expect. The Frame number is either CA7742 or GA7742...hard to read.
Here are some images. I really appreciate any help here. Next job is to inspect the pistons through the spark plug holes, since I was riding it, heard a horrible pop and lost half my power.
(https://alfredstreet.com/images/IMG_0708.jpg)
(https://alfredstreet.com/images/IMG_0711.jpg)
(https://alfredstreet.com/images/IMG_5634.jpg)
(https://alfredstreet.com/images/IMG_5630.jpg)
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japanese front brake? Nice looking bike.
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Good eye. I have the (I think) original front wheel, but this one was on it when I got it.
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Frame is CA7 also 1955 matching Numbers *good3*
Barrel seems to be thickflange A10.
Unscrew the plug and find out the stroke with a spoke or similar.
I ll be shure it will be a stroke with 84mm like the 650 A10.
At the under side from the carbmanifold there will be a Number like 67-1122 or 67-1126 or 1549 and so on.
This Number will tell us what head it is.
This brake will be much better than any BSA brake *smile*
regards Klaus
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Thank you Klaus. It’s going up on the table tomorrow after I get a KLR off it. I’ll get the top end number and measure the stroke. Thank you!
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Looks like an Enfield TLS. Does it work?
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This brake will be much better than any BSA brake *smile*
Clearly Klaus hasn't tried a properly set up 8" H/W or a late 60's TLS then.. ;)
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Good old BSA. Development was by incremental change, not radical updates..... The result is that later and early parts can be mixed and matched as here. Rear is the later ( 1958 season ) swing arm hollow spindle type with right side cable brake full width hub. I'd reckon inside the motor will be far from standard. Primary chain case is also late type (with clutch adjuster access plug) . Looks to have had extensive upgrades and is far from being a factory spec. bike. On early frames wrap around steel sheet on the headstock only extends about halfway up...later frame...goes to the top. It will be C Series, early type, Klaus on the money here.
As a first step take off the sump plate, see what debris has come down. Cylinder bore of 70mm is A10. This is also the diameter of the combustion chamber....unless the head fitted is A7, 66 mm. WRONG. Externally they are identical and the bolt holes are the same.
Next..... Arrange long term finance!
Swarfy
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G'day ct.
As mentioned the A7/10 can be a real mix'n'match.
My Cafe A10 started life as a 57 A7SS and raced as such.
I have my grandads axe, it's had two heads and five handles *whistle*
Cheers
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Hi musky are you the custodian of Triggrrs brush?? As well.p
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Hi All,
In addition, the front fork sliders with the screw in spindle ( left hand thread) are to suit a single sided or 190mm hub
Rear brake with the lever downwards is from 1960? Onwards
John
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Much obliged to you all. By the way, this bike was running, and I was enjoying it up until there was a pop and I lost 1/2 my power, pulled over and called my son to bring the trailer. Before I put this on the table and start taking it apart, I wanted to make sure what parts I was going to be looking for; A7 or A10. Thank you to Klaus, Musk, Swarfcut, chaterlea25 and all, I feel I can start with this. Thank you all. Very much appreciated. Looking forward to getting her on the road again. I'll probably be posting in the A7 & A10 Engine threads. Cheers!
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A few words of caution. Fixings into alloy are BSW... "Whitworth". Majority of other fasteners are BSCy, also known as CEI, a fine thread used on bicycles, head bolts are BSF.
Rocker box has 4 main through bolts into the head and 4 corner studs PLUS a bolt at the back under the rear tappet cover. Pushrods are a pain to replace, plenty to read on the forum about this, skill of a gynaecologist helps. Centre head bolt deep down is at an angle and is removed first and replaced last.
Don't lever on the fins... They will break off all too easily. A set of correct fitting wrenches is a must.... Modern metric Chinesium stuff is a waste of time.
Probably telling granny how to suck eggs here, but worth passing on these experiences for those folks who don't.
Give us a run down in the engine section of how it went from go to stopped. Conundrum solving is a game on this Forum. Also search for the topic "Great Mechanical Disasters" on the forum... If it's still mainly in one piece, count your blessings!
Swarfy
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Frame is CA7 also 1955 matching Numbers *good3*
Barrel seems to be thickflange A10.
Unscrew the plug and find out the stroke with a spoke or similar.
I ll be shure it will be a stroke with 84mm like the 650 A10.
At the under side from the carbmanifold there will be a Number like 67-1122 or 67-1126 or 1549 and so on.
This Number will tell us what head it is.
This brake will be much better than any BSA brake *smile*
regards Klaus
Why does that frame number look like GA to me - seems like that 'C' has a little tail??
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Frame is CA7 also 1955 matching Numbers *good3*
Barrel seems to be thickflange A10.
Unscrew the plug and find out the stroke with a spoke or similar.
I ll be shure it will be a stroke with 84mm like the 650 A10.
At the under side from the carbmanifold there will be a Number like 67-1122 or 67-1126 or 1549 and so on.
This Number will tell us what head it is.
This brake will be much better than any BSA brake *smile*
regards Klaus
Why does that frame number look like GA to me - seems like that 'C' has a little tail??
This little tail is saggy, from a G it is erect. *smile*
regards Klaus
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Oooooooerrrrrrrrrrrr *whistle* *wink2*
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Swarfcut, absolutely invaluable advice. Fortunately for me, I got some wentworth wrenches from the guy I *smiley4* *smiley4* it from. Then, at my first So Cal BSA owners club meeting, I won a full set in a raffle!
I’m sure I’m going to need some penetrating oil. Normally I use WD40, but I bet people here have better suggestions.
It’s going to be a couple days before I get this on the lift. The better half goes in for hip replacement surgery today, so I’ll be playing nurse Ratched for a bit. ;^)
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Hi, I think the frame is restamped. BSA twins has same engine and frame numbers since 1967.
Regards Markku
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I would agree. Someone's made the frame number the same as the engine number.
If it's not a problem for the authorities then why worry?
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Hi, I think the frame is restamped. BSA twins has same engine and frame numbers since 1967.
Regards Markku
I suspect the same! It’s pretty unusual for the engine and frame to be the same on these older bikes.
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Front torque arm is in compression! Rather you than me.
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I don't think that is a CA7 series frame. 742 would be 1954 season, the photos show a number of features not early CA7.
It has a steering lock lug and the top engine mount on the down tube is the cast/forged lug. An early CA7 would have neither, the top mount would be a simple welded on tube.
It has a hollow swinging arm spindle, cross over brake and swinging arm to match a full width hub which did not come in until the 1956 season and the EA7 series frames. CA7 frames would have a solid spindle of smaller diameter.
It has a rear brake cable stop which takes the cable straight back for a brake plate with lever pointing up as used on the EA7 and FA7 series frames but not the GA7 series.
So it is a bit of an enigma.
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Front torque arm is in compression! Rather you than me.
Yes, that black painted steel strap looks ill-conceived as a stay and it holds the cable at a bad angle too.
There are some dangerous amateur engineers around.
(https://i.postimg.cc/dQpHRTNt/IMG-5147.jpg)
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That front brake is the wrong way round - hence the stay being in compression instead of tension.