In need of Rex-toration

If you’re offered a bike that has been restored but built from all the wrong bits, most people would advise you to avoid it. But this is the only one in the world – and Rick happens to have the right bits...

Iguess we’re all experts at finding excuses to buy more bikes, but honestly I didn’t plan to buy this Rex Acme side-valve from H and H’s December 2020 auction. I already have a Rex Acme, a 1927 350cc TT Sports model that sums up what’s great about vintage bikes to me – low, fast and drop-dead gorgeous. Despite having been restored for museum display, this bike was such a mix of bits of different ages, I wasn’t even sure it was a Rex Acme. It was too clumsy-looking and nothing like any model I knew – and there’s so little reference material on such obscure bikes that cases of mistaken identity do occur.

However, included in the lot was an old 1956 log book which revealed that not only was it a

Rex, it had also originally been a 350cc TT Sport from the first year of manufacture – 1923.

Well, that was a long time ago and being a bit of a Rexmaniac I could see very little was still original. You know, us rivet-counters get a bad name, but I defy anyone looking at the latest model of their own bike not to pick out all sorts of tiny changes: different kill-switch, lower mirrors... stuff nobody else would notice or care about. Old bikes are the same. I knew the Rex forks were wrong – similar to 1926 type, but the tubing was too thick, clearly 1928 or later. You’d think 1920s girder forks are 1920s girder forks, but no. Early on, bikes followed then-popular female form – skinny and diaphanous; put 1928 forks onto a 1923 bike and it looks like a flapper wearing rigger boots.

The brakes, originally belt rim type, were later drums and didn’t fit. Worst of all, the two-year-only, racy overheadvalve top end had been replaced with a gentle side-valve. Throw in bulky, pattern mudguards and a load of post-war bits artlessly disguised under nickel plating, and the only bits from 1923 were the bottom end, frame, gearbox, magneto, brake pedal and tank – and that was painted the wrong colour. Any sensible person would give it the swerve.

Well, sensible or not, by chance I had some of the bits to put it right. Besides, that old log book showed that one Jesse Stephenson from Normanton had owned it from 1925, taxing it continuously from 1956 until 1968 – good for him! The bike changed hands in 1970, and then the National Motorcycle Museum bought it in 1984. Twenty years later it was dragged out of the devastating 2004 fire at the museum, scorched but largely intact. Somehow, I felt I owed it to Jesse Stephenson to rescue it again... mind you, thinking about it, it was probably him that had fitted all those wrong bits!

So I decided to go for it – which meant entering the online

auction, a new experience that left me very apprehensive. Alone with your computer, you can’t even watch what others do – just sit there with a finger over the ‘Bid Now’ button; how do I know it works? I wasn’t keen to put a practice bid on something else, in case I ended up buying that as well...

Despite my fears, it all went very smoothly. Each bid amount came up on screen; I just had to press ‘Go’ or ‘Fold’. Beforehand, I wrote out my potential bids including commission, so I knew what each would cost with everything added to avoid getting carried away.

It was all over in a flash. I bought the bike with my final bid – farewell lockdown savings! – but I consoled myself with the thought that fixing it shouldn’t cost much. It’s a ready-restored bike and I already have most of the bits. Although, of course, it isn’t that simple. Older bikes weren’t restored by the museum’s own team back when the Rex came along. I don’t know who did this one, but it’s typical of the 1960s school – make it look like new and be able to chug round a rally field. OK, a museum’s priority will be about the same, especially with a low-profile bike like this, but it was still disappointing to find worn-out points in the magneto, a lug broken off the barrel and a knackered chain.

So am I downhearted? Of course not. This is a keeper; Rex Acme was a tiny company and probably made very few ‘TT Models’ in 1923. I doubt if there’s another one left in the world. However, I know for a fact that it has a celebrity cousin that exists to this day – one of the actual 1923 TT bikes; it’s intriguingly different but survives in a collection on the Isle of Man. It’d be good to get them together some time... but I need to get this one into shape first.

‘PUT 1928 FORKS ON A 1923 BIKE AND IT LOOKS LIKE A FLAPPER IN RIGGER BOOTS’

Original overheadvalve top end has been replaced with a sedate side-valve

The bike Rick bought is clearly different to its original state, shown in the cigarette card (inset)

Rex Acme were quick to capitalise on their success in the 1922 Lightweight TT

9 The spring end’s not even secured properly; I’d guess the spring was originally contained inside a shroud that’s been replaced with an open spring for looks. Glad I didn’t try riding it now!

7 This later wheel is too wide for the frame anyway – the rear frame tubes have all been bent outwards to get it in. OK, plenty to do there – what about the front end?

5 Why? Because while the original silencer was round, like a little cake tin; this ’30s repro-type is too fat to fit. This ‘baffle’ is a bit of a choker too – it won’t be going back on.

6 New brake linings was good news, but not the copper water pipe cam-bush or the brake arm and rod untidily extended to fit around the fat exhaust – it all needs sorting.

4 I can’t move it over because the spokes are already rubbing on the silencer and I can’t move the silencer further out as it’ll get in the way of the rear stand.

8 It needs a slimmer ‘guard, but look what happens with the suspension compressed! The spring bursts out like a hernia and collapses the front end; you can’t ride it like this.

1 Original thin steel mudguards were flexible to facilitate wheel removal. Thicker, unyielding replacements have been fitted, making it impossible to remove the wheel.

2 The mudguard, chainguard and carrier had to be removed just to change this rear tyre, it’s never seen tarmac but shows the bike’s close escape from the 2004 fire.

3 Hmmm... I seem to have pulled a loose thread here. The back wheel’s way off centre. The sprockets don’t line up properly, either, so it’s spaced wrongly.

10 I bought this engine for its rare 1923 ohv top end, but it has sat in my glass display case ever since. Much better to put it back on a bike, although at first I planned to run the Rex as it was.

18 After a clean-up , the bottom end was ready to be put back together and in the frame ready to fit the ohv top end. Wonder how long it was a side valve?

12 Up-and-down plunger also rotates, opening in-and-outlet ports. Mistime it on assembly and it won’t do its job. Shame it got cut about, it’s not hard to fix.

15 These ashes show how close this bike was to disaster. I decided it’s not worth trying to run it as it is. Better to pull it apart and check it over properly.

17 Crank is original 1923 type; flywheels were full circle after this. A later conrod has been fitted, maybe the original went with the original top end.

16 The crankshaft bush had moved slightly, eclipsing this oil hole. I’ve machined an oil groove around the outside; if it shifts again oil can still get through.

13 I didn’t expect to find a standardbore piston; although the cylinder has been relined. Valves are ground in and everything looked OK. So far so good...

14 ... until I took off the barrel to check the big-end. This washer was all that was holding together a broken lug. Maybe I’d better fit the new top end after all.

11 What’s this? This oil pump is back to front; plated outlet should be in front. Someone’s hacked the body about to get it to fit; it must be pumping the wrong way.

25 A perfect fit... but pride came before a fall. The compression ratio was 14:1!! Back to the drawing board. But then I found something in my jumble box that I’d missed before...

22 Piston skirts are often ‘oval’, you can offset the piston left and right to turn off the necessary couple of thou. Amount of offset determines area reduced.

24 A ‘foreign’ piston may not fit over the conrod, needing machining of pin bosses. This was the other way around, so I made a slightly wider small-end bush.

26 This 350 Ariel piston is 1mm bigger bore. It fitted neatly into my 1mm oversize barrel with no mods and gives a 6.8 to 1 comp ratio. You have to laugh!

23 I had to skim as much as possible from the crown. Old, low-comp engines are pretty tolerant, but I wouldn’t drop below 2mm thick in the centre.

19 Early barrels are taller than later ones and pistons are unobtainable. I don’t have measurements, but I have early and late 250cc pistons to compare.

21 I used an independent four-jaw chuck and measured all diameters (they decrease bottom to top) and turned down, deepening the ring grooves.

20 Scaling up to a later 350 piston gives an idea what’s needed. This high-crown piston is from a 650 AJS and looks big enough to machine down.