What Frame is this?

[Worty]

Oooooooerrrrrrrrrrrr

[ctjanney]

Swarfcut, absolutely invaluable advice.  Fortunately for me, I got some wentworth wrenches from the guy I  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.  ;^)

[BVSR]

Hi, I think the frame is restamped. BSA twins has same engine and frame numbers since 1967.

Regards Markku

[Rex]

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?

[ctjanney]

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.

[Sakura]

Front torque arm is in compression! Rather you than me.

[JulianS]

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.

[Triton Thrasher]

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.

[RDfella]

That front brake is the wrong way round - hence the stay being in compression instead of tension.