Honda CB250 – Cafe Racer Build !

by smartmotorcyclingguide, posted in Safety, bike maintenance & other guidance, Uncategorized

In 2019 I embarked on my first Cafe Racer build!

The sections below are just a simple overview of how the build progressed – including the major things that I learnt along the way. Visit and Like our Facebook page if you enjoy motorcycle related content!

Before I take you with me on this adventure – I’ll give you my ‘up front’ check list for any Cafe Racer build! Numbered below is a shortlist of a few things I have learnt from my first time on this journey. I will definitely try another build (maybe soon so watch this space) but the points below would have really helped me if I was starting out on this process again!

  1. Buy a ‘runner’ with all parts of the original motorcycle actually ‘on’ the motorcycle if at all possible. Buying a motorcycle that comes in parts is asking for trouble – there’s no way to tell if all the parts are there and no way to tell if the engine is in any way good. Even if you plan replace all the parts – I found that I learnt a massive amount from taking the old pieces off!
  2. Do not under estimate the time commitment required. I worked at this project every other night for around a month and a half, I was organised. (This was not just a ‘cosmetic’ build – see details about the gearbox and cylinder heads below!)
  3. Be sure that your base bike is ‘common enough’ that there are plenty of ‘retro fit’ parts or breakage parts available (search eBay before you buy the base motorcycle to check that there is a good number of listings that at least mention your prospective machine)
  4. Check the gear box, and examine the smoke from a cold start. Unless you are a up for a really big challenge make sure the gear box is running cleanly up and down all the gears. If the exhaust smoke is blue – you’ve maybe got oil ingress issues coming into the combustion cycle – which means at the very least you ‘could’ be looking at a top end tear down and rebuild. White smoke more often indicates water ingress, a fueling issue, air / carb issue, whilst black smoke can indicate similar issues as above or compression problems: the combustion cycle and associated pressures may not be burning the fuel efficiently.
  5. Create and stick to a budget! After you’ve built a really neat budget, with lots detail , take the total and add 20% : I promise you the project will overrun. The biggest mistake I made when it came to budget considerations – was not considering I might have to buy lots of additional tools which I did not already have in my arsenal – a Torque Wrench, a Feeler Gauge..do you think you’ll need a Carb Balancing Kit?
  6. Buy the Haynes manual – please don’t even hesitate on this one – especially if you’re delving into the engine. This was my bible for this build!
  7. Keep your work-space tidy and organised. When you take pieces apart – either tag them – or set on a piece of paper or cardboard underneath them – write a note about that part on the paper to help in future reassembly.
  8. Have a vision! Be sure you know roughly where you going – things will change along the way but it is important you have an end goal for your newly created machine. Use Pinterest to create a board with images of inspiring examples to get the juices flowing. Check out our Pinterest Boards when you are on there!

The story begins with bargain!

I set my bike budget at just £500, and gave myself £400 for the rest of the build. I did some research and decided a Honda CB250 model circa 1980’s would be a good option. I watched a few of these come and go on Gum-tree / Craigslist / Ebay… BUT.. I was patient. Then one Saturday morning I saw a 1980 Honda CB250 Superdream come up for just £250!

Yes, it was too good to be true – it looked stock (and ‘restored clean’) in the pictures but….

It was running very very smokey (I mean – I couldn’t see the Sun after starting it). The gentleman who was selling it had tried to solve this himself and bought a couple of separate engine heads – but he just didn’t have the time to investigate or put the time into swapping out an alternate head for the existing one.

Sadly it wasn’t the back tyre causing the smoke on my Honda 🙂

The second, and main issue, was that the 2nd gear was ‘lumpy.’ While it shifted into 2nd OK – it made an awfully unpleasant notching & grinding noise. The other gears appeared fine, and the clutch engaged OK, but something was very wrong with the gearbox.

As well as the spare engine head unit – the seller had also sourced a reclaimed gear box from eBay – but again he simply didn’t have the time to do a full engine dismantlement and reassembly. The bike had been sitting in his shed for years – an abandoned project.

If I bought this – I knew I was in for a full engine dismantlement and reassembly – and all of this on top of the other ‘Cafe Racer’ modifications and additions I wanted to do!

In hindsight – as per my ‘list’ above – I would definitely look out for a more mechanically sound engine, as per my list above!

So, with almost zero mechanical experience (but a willingness to learn) , I paid £250 for a running (very very smokey) Honda CB250 SuperDream, with most of an entire spare (used) engine thrown in!

Just a note : the story and images here are a not a full guide on how to build a cafe racer – it is just a short insight into SOME of the trials , tribulations (and fun!) of my journey, but I hope you have fun reading it!

Now, while I highly recommend the Haynes Workshop manual – it still takes a lot of mechanical common sense to tackle something like this. When it comes down to it – you basically have to start unscrewing things and stripping the thing apart.

I bagged and tagged sets of screws and bolts as I went: in fact I put everything I removed that was small enough into bags, my advice is to write a note on the bags to tell you where the parts inside belong! (Even make a note of the Haynes page and paragraph you are on!) This little bit of extra time and care taken ‘up front’ really saved me a lot of pain when it came to reassembly.

So here we go!

The first job was to get the engine cleanly removed from the frame! This took me about two nights & an afternoon. The process of engine dismantling and rebuilding (which follows below) was a fantastic learning experience that I recommend to anyone interesting in motorcycle technology.
My Honda CB250 Engine – ‘on the bench’. (The little box of sockets in the picture are one of my favorite pieces of kit – you can pick them up from amazon here)
Here we see the rocker mechanism after removing the cover : the springs you can see sit on top of the valves, keeping them closed. [When putting the engine back together this is the stage where you set the ‘valve clearance’ gaps using a feeler gauge.]

The rocker arms ‘rock’ back and forth pressing the valves open / closed in a sequence which is regulated by the timing chain at the center of the picture. The clearances between the end of the arm and where the arm presses on the values to open them, are adjusted by the lock nuts you can see at the end of each arm. Many older motorcycles and some new dirt bikes and trials machines still require frequent valve clearance checks.

There was so much to learn at this point, and I was only at the very beginning of the dismantling process! Please understand that I’m writing this article as if you’ve not seen inside a basic motorcycle engine before – I am deliberately just giving you ‘a flavor’ by covering some of the technical terms you’ve maybe heard mechanics talk about before!
This is the ‘nut of the devil’ otherwise known as the clutch hub lock nut. It was one of the most challenging parts of the whole disassembly! I fashioned my own clutch nut removal tool ; which I would NOT recommend – just buy one.
While the Haynes manual did a good job explaining how to make a home made a lock nut removal tool – the job of actually releasing the lock nut was awful. I still have nightmares.
A ‘few’ nights later – the picture above shows the internals of the lower half of the engine exposed. You can see the second gear cog has a tooth missing! [The cog closest to the right of the picture]. Problem identified! The spare engine components thankfully included a spare set of gear cogs – but these things can picked on up from eBay fairly easily. You can also see in this image the gear change barrel – when it rotates, it causes the gear selector forks (which sit in the deep groves of the barrel) to get moved back and forth, translating the sequential up & down movement of the input foot lever to the transverse movement of the forks along the axis of the gearing. Fascinating! (Well I thought so!)
I began the painting a little early (with heat resistant engine paint of course!) then realized I had neglected to swap out the head unit! (So another few nights later, after having to buy more gaskets, the new head was attached and the engine above was almost ready (again).
I spent a considerable time reading and learning how to strip back and then how to paint a tank. Here are some my biggest learnings to help you if you tackle a project like this!
1. You can use spray cans (that’s what I did) – but yes, using a compressor and sprayer will be a better job.
2. Sanding down to using (eventually) a super fine wet and dry grit to achieve as good a surface as possible, is the absolute key to the final finish looking good. The final paint finish will only ever be as good as the preparation to the surface you have put in. Don’t skip the primer (and don’t skip recommended number of coats).
3. IMPORTANT – Be sure to buy a proper petrol proof lacquer. The first lacquer I used was labelled ‘automotive’ – when I splashed a tiny drop of petrol on the tank (the first time I was testing the bike fueling) – a bubbling paint blister greeted me. Yes – I had to paint the tank again.

Next time I would definitely consider either buying a ready painted tank or paying for a professional to do this – but it IS possible for an absolute amateur (like you or me) to get the job done!
I tried to create my own seat from the existing one – to cut the story short – I simply was not happy with it. A £20 eBay cheap option came to my rescue, or so I thought! The universal eBay cafe racer seat I found – wasn’t really universal but I expected that! I had to work through a considerable amount of inventive fabrication to get the new seat (the one you can see in the final pictures) to fit.
The challenge was getting it to mount with lock nuts flush to the tank and frame. Overall this was one of the most time consuming and challenging pieces of the build. (I spent longer adjusting and getting the eBay seat to fit than I did in fabricating my own seat that you can see in the images above!)
Cleaning the covers brought me the into the entire new “world” of metal polishing techniques. I’ll write a blog post on this some day. Again – preparation of the surface is key. I did buy a cheap set of metal polish attachments for my drill (and the multi-tool was also invaluable). Again – I could have spent another month getting the metal work to shine like like sun – but I wanted to it be good, rather than perfection. The image of the covers above is before treatment. The image below shows carb covers, before, and then after a little work with a polish kit. I then finished off to a reasonable finish with Autosol metal polish, amazing stuff.
I have only a few photos of the carburetors ‘mid-build’. One of the keys was buying a good Carb cleaner (basically – petrol based solvent!) to ensure that all parts were thoroughly cleaned. If you have a pressured air gun- use it here. Check that your diaphragms are in good order – if needed just replace them when the part is in pieces!

Carburetor valve setting and needle adjustment is another entire area of study and learning – I’ll not go into it here!
If your other half has an ultra sonic jewelry cleaner – this is a fantastic use for it! Strip down everything on the carb and pop the pieces in there! You can pick up these ultrasonic baths easily from Amazon!

I also bought a carburetor balancing kit – difficult to use (you’ll find some instructional videos on YouTube) : this is the one I bought here! [A balancing kit is effectively a vacuum strength measurement device – it gives you a reading which allows you to set each carburetor’s intake to develop the same level of base vacuum draw in each cylinder. ] I’ll maybe write a separate blog on to give some information around carburetors at some point!
You can see here I tried to paint the springs using a rubberised paint. I didn’t like the finish – it was a very dull matt. Instead I was able to pick up brand new replacement rear spring sets for £30 or so.
I’ll mention here that I also had to learn how to replace front fork seals! Surprisingly not one of the most difficult jobs of the build – just follow any online YouTube tutorial and be brave! (Or, like and follow our Facebook page to contact me if you want to know more!)

I also sourced a ‘seat hoop’ from eBay (the metal hoop you can see in the image above at the back of the bike). I got the old frame chopped off and the new hoop attached after some basic trial and error! (I used an arc welder for this – which was much too strong for this delicate thin metal – but with some perseverance and a few prayers, it held)
When it comes the electronics – take photos of everything for reference, BEFORE you take the parts off the bike. I also marked each wire (if I couldn’t get a permanent marker onto the clips – I used a piece of masking tape.)

I labelled each side of each connection where there was clip joint, starting 1 – 1 ,then 2 – 2 , 3 – 3 , etc , etc. Using the same number on each side of broken apart clip. A voltmeter is also invaluable for tracing wiring connections and for testing when you’re swapping in new electronic components later in the build. Challenges for me included mounting the electronics board – I had to build a new ‘cradle’ beneath the seat (as opposed it being mounted on the side of the stock machine. I also realised late in the build that I needed an updated indicator relay to cope with the new lower voltage indicators I had bought! (Without the impedance provided by the new the relay – the newer indicator lights flashed much too quickly!)
I decided to use the existing speedometer and tachometer. I mounted the old units inside a shiny chrome cover (from China Ali-Express!). Of course nothing fitted as it should have and I had some serious work to get the units to fit in place neatly! Next time – I’d consider buying new dials instead of reusing the existing units.
The paint I used on the rims was a rubberized hard wearing compound – designed to resist stone chips etc. Spray can paint proving its worth again (just be sure to apply even, multiple coats , do not rush, avoid the dreaded runs!)
The Finished Machine – time for a race to a cafe for a coffee.

There was a considerable number of other challenges to get this bike through a UK MOT service and fit for the road (many of which I haven’t even mentioned in the above summary article!). It still had a few niggling issues when I sold it unfortunately – but I was upfront with the buyer that it was still facing some issues.

The best advise I can give you is…just go for it, but be sure you are going to follow it through! Catch up with Smart Motorcycling Guide on Facebook – give us a like over there if you enjoyed this article, I would really appreciate it!

Ride Safe, Ride Smart

Smart Motorcycling Guide