The first step in a project like this is to layout the specifications. Below are the basic parameters for this project. With the correct parts and design, I feel most if not all of these specs are within reach.
Along with these numbers there are also requirements that cannot be summed up in numbers alone, like driveability on and off-road, center of gravity, how easily the motorcycle can be serviced... All of this data factors into the design and will be explained as the project progresses.
The first part that I purchased was a used 2015 Yamaha FZ-07 Engine. This engine has the specs I want... 70+ hp with a great power curve for off-road, small light-weigh footprint, Yamaha twin reliability, endless aftermarket support. The only part of this engine I'm not pleased about is the deep sump oil pan. This might challenge the 10 inches of ground clearance I'm looking for. If this becomes a problem there is hope to dry sump the engine or maybe redesign the oil pan for more ground clearance.
The second part I purchased was a used 2016 KTM 690 Enduro swingarm. This part is very important to the overall geometry of the motorcycle. I took my time and did as much research as possible and found that the KTM swingarm would work the best for this project. This also prompted me to buy the rear brake caliper and rear WP shock from the KTM 690 Enduro. This part selection makes building the rear suspension much easier and has the specs I want already designed in.
At this point I started to take dimensions and create 3D models of these parts. This allows assembly of the parts and a general layout of the geometry to be created and changed until it works correctly. The engine was modeled so the mounting points and drive gear are within +-1mm and the overall shape +-3mm. The swingarm was modeled to even stricter standards. Since the overall shapes of these parts are fairly organic it's tough and time consuming to create models that are perfect without complete disassembly or a 3D scan, both were not options. Having correct dimensions and measurements of the important areas are all that is needed for this project.
The next part that was sourced was the 2016 Yamaha KYB SSS front end. Granted this bike has a Yamaha engine, it seemed fitting to use a Yamaha front end because the KYB SSS forks are really good and can be found at reasonable prices. The forks and the aforementioned WP shock were modeled and made to be working assemblies in the modeling space.