1957 DOT THDX 250 Trials Bike Restoration

Jim’s Project 1 – “DOTTY” a 1957 DOT TDHX with 250cc Engine

First off, use of the word ‘project’ does not imply that this is my primary and sole mission in life. Projects to me are long-term hobbies to fill in the times when a bloke just needs to have some ‘me time’ in the garage. During this project I have changed jobs 3 times, seen all my children finish school, watched Preston North End win a trophy and my house is now (2020) a virtually DIY free zone.

I bought this as my first motorcycle restoration project after spending years modifying and restoring cars for rally’s, sprints and hill-climbs. The main motivator for the move back to motorcycles after an absence of 30+ years was because my shoulder became knackered and I was fed up of moving heavy gear boxes/engines in a small space and spending too much time lying on the cold floor of my garage to work under cars. My previous Bikes included: Garelli Tiger Cross, Yamaha RD200, Kawasaki LTD250, Honda CB125 Twin and a Suzuki GS750.



My lovely Suzuki GS750 in 1982

On the advice of a friend, who said “the first restoration should always be a straightforward one – choose something like an old British bike”, I decided to choose a DOT (Devoid of Trouble!). I fool myself that there were two reasons for this; firstly, it was of a similar age to myself and therefore it would be treated more sympathetically by myself! Secondly, it was made in Manchester, Lancashire, which was the closest bike manufacturer to my old hometown of Preston. So, the basis for this purchase was nostalgia and sympathy – not necessarily good reasons for a purchase. However, it sounds better than the impulse purchase on eBay (which is what it really was).



Dotty on the day that I bought her

DOTs were a marque that were developed after World War 1 and their market was largely small capacity trials bikes. Like many other small British marques in the 1950s, they developed their own chassis and used the Villiers engine as the powerplant. They are not that well known except in Trials circles where they were very competitive in the 50s/60s.



The former DOT Motorcycle Factory in Manchester (now sadly gone)

Unbelievably, I actually bought this bike as a non-runner way back in September 2015, from a chap near Shepton Mallet in Somerset. The bloke had built up the bottom end with new parts from Villiers Services in Birmingham but was absolutely stumped because he could not get any spark whatsoever. He actually said to me “it’s a 2-stroke – how difficult can it be?”. I smiled inwardly and naively thought that I would soon have it running! I took it home to Plymouth (Devon) and tucked it up in my garage. It stayed there for some time whilst I researched both DOT Motorcycles and Villiers engines.

The DOT research was quite easy, although they are not plentiful, there is a good owners club and you can obtain old parts lists and owner’s manuals off eBay. The Villiers research, hit a problem straight off because it was not a standard 200cc Type 9E engine. Someone had replaced it with a Type 35 from a Bond Invalid Car! Please don’t laugh at this because I didn’t. By the way that is what they called the cars in the 1960s (wouldn’t be allowed today!).



Bond Invalid Car with Villiers Type 35A Engine

The other thing which confused the hell out of me was that it had 2 spark plugs and it was a single cylinder! A friend of my brother told me that one of these was for a decompressor cable to stop the engine – turns out that the previous owner just stuck a spark plug in there to fill the hole.



As bought with 2 plugs (top) & fitted right way round with decompressor (lower)

I bought new ignition parts (points), condenser, decompressor cable and activator but it still would not produce a spark. There is no battery with these bikes, it is a 6V total loss system. I spoke with Villiers Services a few times over the intervening years but nothing that they suggested seemed to work. I hate that felling when everyone else’s bike seems to work except your own and no-one knows why. Lots of things were recommended to me and I tried most of them but with no success. As a result, the bike sat covered in the garage and I only progressed the bits that I could do on the frame on an ad-hoc basis.

The fuel tank was cleaned outside and inside before being treated with POR-15 (an ethanol resistant tank liner treatment) and then re-sprayed in silver. I obtained a pair of original DOT Trials shocks to replace the rear telescopic shocks and all the brakes were checked and cleaned. The frame I have kept in the original British Racing Green that it came in.



Refurbished tank in silver & original British Racing Green frame

I then decided that I needed a motorbike lift/bench, so (as yet another diversion) I bought an old hospital bed for £30 in Hereford and cut it up to make my own lift. I had some chequer plate lying around and used up some old spray paint to tart it up a little. Works perfectly, and now Dotty can move up and down (about the only movement she’s had in 5-years).

£30 Hospital Bed which became Dotty’s Bike Lift Table


During one of those moments where you sit staring at the bike wondering what the hell to do next, I realised that the engine was not fitted properly and that it was canted backwards. The 250cc engine was obviously a bit bigger than the 9E and it had been loosely fitted using the original engine mounting plates. I removed the engine and then made some engine mounting plates which allowed the engine to sit properly in the frame. Feeling buoyed by achieving something positive with the engine, I embarked on stripping down the ignition again and starting afresh.




Original points (top) and Stator plate (lower) stripped back

I decided to make it into a 12V battery system and provide the bike with LED lights and indicators (LEDs don’t work on 6V systems). I mounted an aluminium battery box under the seat and then fitted a very expensive electronic ignition kit. The only place that you buy these kits from is through Villiers Services who have the only franchise for them.

They emailed me back when I placed the order and asked me to send them some photos of the engine casings and engine ID plate. It turned out that the engine is in fact a Type 32A with a Type 35A chain case (which has the engine ID plate on it). It’s amazing that you take for granted that the engine number is correct but then someone who is used to looking at these things regularly can spot these differences straight off. However, that would partially explain why the new points, etc, did not provide a spark for me and the previous owner.

I am now (July 2020) quite a way into making my own loom to bring everything together. The battery, fuse box, and wires are now all in place. I am in the process of wiring in the flasher relay and lights. Motorbike electronics can be a soul-destroying task at times and I have found that I have to be in the right frame of mind for it otherwise it is a waste of time and effort.



Things were going well until I bought another project bike just before the Coronavirus lockdown (supposedly for when Dotty was finished) which was a Honda CB250RS (Bessie). The reality is that I have been bouncing around between both projects and have also restored an old Puch folding pushbike.

I made great progress with Dotty during the Coronavirus lockdown period but I have had to leave it for a while because I needed to do something different for a bit. The distraction of Bessie and the Puch were much needed respites from the wiring loom. So Dotty is still on the ramp and looks at me all expectantly when I go into the garage but she hopefully won’t have to wait much longer to be finished off.