The spacer OD on my BA (which conveniently is sitting on my bench in bits) is 44.73mm at the least worn section. That would seem to be correct for the seal ID that you have of 44.45mm.

To anyone - when fitting the plate and nuts on the spring, how do you compress the spring in enough to get the nuts on?

I tried many ways of compressing the spring however I finally got round to making a bespoke compressor.
spring tool.jpg
This has a big advantage in that I can assemble the ...

Where did you find that? I looked everywhere when I needed to make a pushrod - couldn't find anything which wasn't in the US and a daft price.

It was a while ago I last got some. I think it was West Yorkshire Steels, however the availability and price seemed to vary with what they had in stock at ...

The best (closest to the original) tubing I have found is 4130 Chromoly Steel, OD = 7/16”, ID= 3/8”, Thickness = 1/32” (21G).

4130 Chromoly tube.jpg

4130 alloy tube is readily available. It is used in aircraft and vehicle frames and is extremely stiff and thermally stable. The size above is ...

I use a slim 7/16" AF six-sided socket with the end ground flat to reduce the internal chamfer. This sits flush to the sludge trap flange and perfectly into the flywheel hole. It has worked successfully for me on several previously user-mangled sludge trap nuts - probably because it engages on the ...

Both these look dubrious to me or am I getting too suspicious in my old age?
https://www.ebay.co.uk/itm/128016587921
https://www.ebay.co.uk/itm/307120065853

Cam,
I think you have a brake plate from a pre-1931 single. The angle between the frame lug slot and the centreline of the brakes (piccy 1) on your plate is much narrower than that on a 4F.
cam brake plate 1a.jpg


The 1935 4f has a much wider angle (piccy 2)
1935 4f 1a.jpg

As always, I am ...

Have you checked for blockage in the other crankcase breather i.e. the one on the side of the cylinder block from the tappet chest? If this were blocked then the only route for blow-by would be into the timing cover, possibly causing your symptoms

Also check the blow hole in the crankcase from the ...

It looks like I have a minor challenge here.

Not a challenge - a learning opportunity

Keith,

These pictures are of the original toolbox on my '49: The mount is quite close to the ridge. Possibly your pattern box is narrower than the original so maybe you could pad the rear mounts out a bit to take up the difference.

Pete