I'm experimenting with two basic ideas around construction in these designs...
The first is to compress shapes - making all the key forms of the engine squatter, flatter, more solid looking. The mud guards are tight to the top of the tires and I'm also compressing the wheel base - playing with how far apart the wheels are from each other in relation to the height of the wheels themselves, this further adds to that compact look.
The second main technique I'm employing is to push the perceived visual centre of gravity on the bikes as low as possible. I'm angling frame lines and handle bars down, lowering engines, and keeping as much of the bike's gear below the top of the wheels as possible. This helps to make the bikes feel heavier, more substantial, even when drawn in an exaggerated style like this.