1974 Honda CB250

Hello! My name is Nick and I am 19 years old. This bike is my first attempt at building a custom bike to a high standard and it has been a labour of love alongside my day job as an apprentice engineer. I could list all the parts I fitted and call it a day, but I thought it may be more interesting to write this as more of a story. All of the work has been done by me, in a single garage that is also occupied by a Triumph Spitfire, with hand tools, an angle grinder and a cheap MIG welder.

I started off with a fairly standard, but very battered and neglected example of a CB250 that was last used in anger way back in 1989, where it was put in a shed and changed hands a few times before finally coming in to my possession. My plans for the bike changed a few times but my ultimate goal was to have a bike that functions as well as it looks. I believe that patina is more beautiful than a brand new sprayed item, so from the very beginning I knew that the fuel tank and headlight bucket were going to be as they were on the bike when I got it. It took nearly 50 years to look like that, and i wasn’t going to be the one to interfere with it.

During the process of stripping the bike down, I decided that fitting the forks, wheels and brakes from an Aprilia RS125 was the way forward. With the 4 piston front brake on a sub 140KG bike, certainly slows you down quickly! Now, I know that having alloy cast wheels will upset the purists out there, but I think it makes the bike stand out, despite dividing opinion.

There was of course one small issue with all of this – no way were parts from a 2008 sports bike going to fit the old girl. To avoid significant over-investment into something that could fall through, i started by simply getting hold of a top and bottom yoke, so that I could do a test fit. The steerer stem was the perfect length and with some trawling through the internet I managed to source some bearings with the correct dimensions to marry the Honda head tube to the Aprilia yokes. An additional impulse buy of a used Cagiva Mito steering damper was fitted as well at this stage.

With that, the rest of the front end conversion was simple. The rear wheel fitment was also surprisingly easy, and the only swingarm modification required was to enlarge the axle slots to accept the thicker Aprilia axle, even managing to retain the original chain tensioner mechanism. The tyre width clears, and the only major adjustment remaining was to offset the front sprocket, to allow for a straight chain line. In doing so, I also had to space out the clutch cover and in turn the whole mechanism inside to clear the new sprocket position. With that, essentially the whole fork, wheel and brake conversion was done… (more on this later)

I did the usual frame modifications, removing all unnecessary tabs, welding a new rear loop in, with an integrated tail light. To keep the loop looking clean from all angles, a sheet was welded to the underside, blending it in to the battery box and making it look like it came from the factory. This helps with reducing the chance of dirt and water ingress as well, since it acts as an under tray. During my apprenticeship course, I learnt how to use a lathe, and around about the same time I was making the rearsets (utilising the factory rear foot peg mounts and adapting some old parts lying about). At the end of the course, I had some free time and as such I was allowed to go freestyle, so I made the two footpegs, gear peg and paddock stand bobbins out of aluminium.

The exhaust was made from the original headers, shortened down and added some stainless tips, which were made from some mandrel bends I bought online. Yes, it has been wrapped which again may upset some people, but at some point it is my intention to learn how to TIG weld and produce a full system myself. I also would like to add that the side stand had to be fitted on the wrong side of the bike as I didn’t have space on the usual side. This takes some getting used to but I don’t think twice about it now.

Adapting from a rear drum brake to a hydraulic disk brake meant that I needed to find a way of setting up a rear master cylinder to use said brake. After many hours of staring at it, experimenting with different master cylinders, it dawned on me that this might not work. Fortunately, I discovered thumb brakes, and realised this was the way forward. After months of waiting, a second hand Accossato unit came up for sale, which even had a braided hose, the exact length I needed. Perfect!

So, the rolling chassis is complete, I had fitted a fibreglass seat hump and everything was ready to be sent off for powder coating. While waiting for this, all bare aluminium parts were rubbed down with scotchbrite to leave a brushed finish. I also rebuilt the carbs, the forks and the brakes.

After getting the frame back from powder coating, it was time for the final assembly. The rebuild process was quick and easy, however the most daunting thing was in my way. Now I love all of the mechanical work, the fabrication and the alterations, it is what draws me to customising bikes, but one thing that I cannot get my head around is the electrical side of things. I needed to rewire the bike, so this was probably the single most time consuming job on the bike. I fitted a Boyer Bransden digital ignition system and rectifier to allow me to use a lithium battery, the indicators are all LED, as well as the tail light and brake light. The headlight is a remanufactured OEM equivalent.

With the wiring complete, it was time to start it. With it being a Honda, of course it fired right up, but had several bad oil leaks, meaning that the engine had to be rebuilt, if only for the purpose of replacing the gaskets. When opening it up, I found the the left hand piston had a chunk missing from the skirt. I’m very glad I caught this before any catastrophic damage occurred. So, new pistons, rings, cam chain tensioner and re honing of the bores and all new gaskets and seals.

At this stage it is basically a brand new bike, and it has taken around 18 months to get to how it is today. I have learnt so much from the building of this bike that I know will help me out in my future career. I cannot wait to take her out for a proper ride once the world is back to normal. Thank you so much for taking the time to read this and I hope that it has been a good overview. There is so much more detail to go into about everything I have done on the bike, so I hope the photo comes through with good enough quality to see that hundreds of hours have gone into it. Please don’t hesitate to ask for more pictures, I have plenty!

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