I don't remember if I posted this before but the following are the Ariel-specific jigs, fixtures, and special tools I used when I completely rebuilt my 1928 Ariel:
Engine
Sight glass cup blank off
Crankcase mouth alignment plate
Engine shock absorber spring compressor
Rocker grinding jig
Faux variable-length pushrod
Torque plate with spacers
Valve guide insertion stop
Dummy valve guide
Oil line pressure test kit
Faux 9½" crankshafts:
0.874"
0.874"/0.947"
0.859"/0.961"
Faux Imperial main bearing
Faux 62 mm metric main bearing
Metric main bearing honing jig
Camshaft electroplating chamber
Big end mandrel
Protractor adapter/spacer for main shaft
Protractor adapter for cam
Engine cases machining jig blocks
Base for mounting engine case to mill
Spacer/jig to mount engine case to mill
Jig to mount engine case to mill
Crankshaft sleeves for use on balancing wheels
Rod alignment gauge
Oil flinger shim soldering jig
Spacers for engine lifting jig
End float indicator holder
Oil pump disassembly kit
Magneto
Magneto sprocket extractor (stock)
Magneto sprocket extractor (variable sprocket)
Rod for rotating magneto
Gearbox and Clutch
1¼ BS deep socket for gearbox sprocket
Clutch hub sprag socket
Cutch hub holder
Socket for adjusting tension on clutch springs
Sleeve gear bush drift
Frame/Cycle Parts
Brake pedal extractor
The following photograph shows most of these, most of which I had to fabricate myself.
Of the items in this photograph, only the three spanners are commercially available. I suppose I could have omitted the smaller two and instead counted them as part of general purpose "Whitworth" spanners, but they're thinner than typical combination spanners and that thin attribute is needed for their use on the Ariel (e.g. the smallest one is for adjusting the tappets).
The wood block at the bottom of the photograph may seem out of place, but it is essential when working on the crankshaft. I would have replaced it with something machined from metal, except I prefer the softness of a wood block. The large round jig to its right also is extremely useful, so I included it in the photograph even though it is of general use for pressing together other crankshafts as well