Updated: Nov 18
When you first start your journey into the custom motorcycle world , no part is more fun and makes you feel like you are actually a custom bike builder more than taking the angle grinder to a frame and having at it. However, as I have said before, you can't just go hacking at the bike. This is especially true if you are planning to significantly alter the subframe. This bike, like my others is going to be a single seater. So, it's necessary to cut the pillion section from the frame. In this case I am planning to keep the shock mounts where they are. I want to cut off the stock, pressed steel, section of the frame just behind them and close the rear tubes with a seat hoop. Cutting the frame here should open up the original seat tubes that are forward of the shock mounts to allow me to do just that.
There is also a structural, box gusset in front of the shock mounts that I wanted to remove too. So anyway, after a careful long stare at it all, I reached for the angle grinder. I had considered the seat size and length I required, the alignment to the tank and how the seat cowl was going to sit in proportion to them both. You see, this is the point that you have to have worked out your lines and the fit of your major components. You don't want big gaps between your tank and seat or have them at odd angles. You also don't want to end up with a seat that's too short or a cowl that's way too long. it all starts with this cut. No pressure then...
After I had cut out the box gusset and the rear section, for peace of mind, I tacked in a temporary cross section across the back. As I still had a little repair work to do on the underside of the frame, I didn't want the heat from the welder distorting the frame because I had removed some of the key structural parts.
So, out came the MIG welder for the first time in this build. A few years ago I invested in a decent MIG. It was the first, serious piece of kit that I added to my workshop. I certainly could not be doing anything like the work I am now without it. It's a Lincoln Bester 190c. They come in around £500 but by the time you have factored in Gas, regulator, wire and the necessary protective wear, you are probably looking at around £750 to get properly set up. It has been worth every penny though. It was a steep learning curve and takes time and practice and I still consider myself to be a terrible welder. However, I am now at the point where I can be confident in the integrity of my welds while at the same time make them look pretty when I need too. I have a lot to thank Ricardo Churchill for here. He is one of the best fabricators I've seen, (the man built his own canal boat for heaven's sake), and he has been very generous with his time advising me on voltages, gas flow and wire speeds for the different jobs I was attempting. Other than that though, I guess I'm self taught. Learning by doing and making all of the mistakes along the way.
Now, where was I? Ahh, the seat hoop! There are two ways I could have gone here. Classic Honda CB's are a popular choice for custom bike builders so there are a number of aftermarket, pre-fabricated seat hoops on the market. I even managed to pick one up from that popular Brazilian rain forest on same day delivery?!
The majority of them though, like this one, involve you making a diameter reduction. 25mm to 20mm to be exact. 5mm doesn't seem that bad on the face of it but it's very noncable. The idea is that the new hoop fits inside stock tube so it can be easily and securely welded in place. However, I didn't want a visible reduction in tube size. The other problem is that they are made with a standard, 180° semi-circular bend. I wanted to do something a little different for this build. So, an aftermarket hoop was almost certainly out of the question. I started thinking about making my own and toyed with the idea of using a pipe bender to create one. I grabbed a piece of 25mm steel tubing and headed down to see my friend Bob Moore at