Chapter 4. The Good, The Bad and The Ugly

Buying a motorcycle is a voyage of discovery and it’s unlikely that in the cold light of dawn, on closer inspection, the condition of your purchase is anywhere near as good as you thought – although I have to say when I bought my Ducati 748 (or my yellow mid-life crisis as my wife likes to call it) after a quick once with some cleaning products it came up a treat.

As far as the BSA was concerned I never expected too much from the original advert on eBay but knew very well that once I’d driven up to Sheffield it would almost certainly be coming back in the van with me. As mentioned earlier the crank felt solid and turned over OK, but I did notice that the exposed valves were not operating. All the way home I had this nagging doubt as to whether there were actually any components in the engine.

The Good

Fortunately, when I removed the cover, the timing gears, the cams and even the tappets were present and correct, all that was missing in fact were the pushrods. Not only that, but with no more than a wipe down with an oily rag the various components looked virtually new. When I lifted the head, there was a new +0.020” piston to go along with a rebore. I was reaching the conclusion that this engine had been subject to a recent professional rebuild.

The photo below shows the engine at a later stage in the build, with the magneto fitted. Interestingly (well it is to me) there are two idler gears, and the magneto would clearly be running at engine speed. I had by then bought a reprint of the BSA Parts manual for the exact year which was to prove invaluable. This set-up would be for one of several options, for a Maglito magneto, a design that was intended to provide both ignition and lighting – but as owners would say – not both at the same time. I’ll be doing a separate chapter of the magneto in the future.

Another real bonus was having the original buff logbook. I have seen similar offerings on eBay – just the logbook - going for £250! This bike was registered in 1932 by a Mr Robert George Tyley of Muswell Hill. The book has stamps in it up to 1936, by which time it was owned by George William Dixon from Hatfield.

We’ll see later how there were obvious issues with the frame geometry but knowing exactly how it should be set up was proving a challenge. Plenty of photos were available via Google but not of a definition to know exactly what was wrong. Eventually I came across a catalogue for an auction in the US and one of the items for sale was a manual for the bike – with a photo or scan of the cover. It was rather grubby and creased so I asked Perry if he could do something with the image. This is what came back, a perfect line drawing, more than sufficient for me to carry out a complete check of the frame geometry.

The parts book was a great help too as I could now search the internet by part number and lo and behold most of the missing parts from the damaged gearbox were available – and from Draganfly  -at a reasonable price. This is gearbox, new main shaft bearing fitted and ready for assembly.

The Bad

The parts book was great in that I could now see what was missing but it also revealed that in fact there is very little available for a bike of this model and year. Some parts are common with the M20 and I got lucky with the gearbox but even then Draganfly put some items on back-order and they have still not become into stock. 

Another major issue was typified by the gearbox cover, which was damaged in several places. I had plans to get it welded up but realise that if it was damaged in the process, I won’t be able to find a replacement. I managed to track down a previous owner of the bike who was good enough to let me call him. He commented that I’d “bought myself a whole world of trouble” as no parts were available – or if they were would be very expensive. I resolved that what I didn’t have I would either have to adapt parts or an assembly from another bike or manufacture them myself.

The Ugly

The bike looked odd from the outset, not helped by the home-made forks girder forks. I managed to get it looking slightly better by putting a two-inch block under the front wheel, such that the lower frame rails were horizontal and the engine just about vertical. The bike didn’t come with engine plates so the frame would flex significantly, but it was good first step. I don’t have a frame jig, or even a very flat surface to work off, but usually use string lines and spirit levels to line a frame up. I find I can get within 1 millimetre with reasonable repeatability and reckon that’s good enough. What this showed was that the wheelbase was almost 3 inches too short and the rear axle height too low. The white card in the photo below has a cross where the rear axle should be.

I then determined with the aid of the parts book that my rear sub-frame was in fact from a different model. It was certainly a BSA as it has the crude flattening on the lower frame rail to take the lower front engine mounting stud. My subframe is made up of two assemblies, each comprising the chain stay and the seat stay, whereas the correct arrangement is separate chain stays that bolt to the rear lug. 

With a bit of trigonometry and a scale drawing to check I realised I could correct the frame geometry by extending the lower frame rails by 72 mm. Unfortunately this would be at a point where the tube would have a bend. My first attempt was to machine up a couple of extension pieces then bend them, but this didn’t work as the force required over a short length flattened the tube. The second attempt was far better, using a pipe bender to put a radius in a longer length of tube, then cutting two 72mm lengths and turning up some hollow plugs. The following picture is the final set-up before welding, which I’ll cover in the next chapter, with some other details of my build.