1983 BMW K100

The K100 was never a bike I was drawn to, whether custom or not. I could count on one hand the K100’s that have ever caught my eye and made me think – That’s a nice bike. They’re just not for me. If it wasn’t for the guy that owned the bike we would have never built it. I’ve known Ryan for a while now, since my first shop in Mermaid. He helped me find my current workshop and is my go to sounding board for anything Real Estate. A nice guy, and an avid enthusiast.

He had asked me a number of times to build the K100 but I’d referred him onto other shops that never really took hold of the job so after 3 years he came back and Asked Purpose Built Moto to get this thing done for good. The bike was in a state of disrepair after being partially torn down and poorly stored. We started with a game plan for Ryan’s build.

It was to be completely rebuilt with modern running gear, a set of custom wheels to fit a wider tyre on the rear and the engine needed a complete refresh. We soon figured out why the other places never got it finished. As expected on these over engineered german tanks the bottom end looked fine, but it was a top end issue that caused the bike to be parked and resulted in a lengthy parts sourcing and repair process.

One cylinders exhaust valve had locked up and caused some damage to the piston and cylinder wall. We had to search high and low for a set of pistons and the Nikasil repairs don’t come cheap. With this the K100 received a set of oversize valves, some mild porting work and a race ignition upgrade from K-parts holland. The engine got a set of 4 valve throttle bodies, a custom coolant overflow and a manual fuel pressure regulator and gauge. We’ve blasted the cases, re-sprayed and brush finished some select parts before fitting the brick back into the frame to start the styling work.

Up front the K100 runs an Aprilia set of forks + Brakes with custom triple clamps, rear has been swapped out for a cantilever monoshock and K1100 swing arm to allow the wider rear wheel.

Jonich have supplied the specialty set of 17” wheels in a simple Satin black with polished stainless spokes. Now the bike was on its own 2 wheels again Joe from Ride dynamics was sent the bike to overhaul the forks and set the suspension. Returning the forks in an Ohlins Gold, with rebuilt internals set for our riders weight.

We were now free to fabricate the custom subframe, and sheet metal that would finish out the tail and tank. We’ve shortened up the tail for a single seat, and carried the boxy angular look of the tank rearward. Making a simple tail that breaks the frame line and would set the tone for our radiator shrouds. We’ve built in a brake light to the new frame hoop, and made a swing arm mounted plate holder that houses the rear omni indicators too. The perfect way to keep our work on the tail unencumbered.

On the front of the build we had a lot of real estate and functional (ugly) parts to cover.

The bike was previously fitted with an aftermarket radiator grill that spurred Cody’s idea to box the whole front section in. You’ll often see these builds use the same parts that bolt into the front of the awkward tank cut out. We wanted to make our own set up and give the tank a nip/tuck to remove some of the menacing angles on the bottom line of this tank.

We’ve trimmed a wedge off of the bottom rear of the tank, and let that be the jump off point for the 2 piece radiator shroud that wraps around and bolts together in the center to house the new radiator grill in a complete and form fitting set up.

This completed the broad shoulder section of our bike and left the last fabrication job of a tidy front fender and fabricate the bar work to house the front lights.

We’re running a 7” flashpoint headlight here on a custom mount that also mounts the Daytona gauge front and center. This is a tried and trued set up we use on a lot of our bikes. It’s clean, it works, and our customers love it. The front fender is a DIY fender kit, shaped up to suit the style of the build.

The controls up front are a set of woodcraft clip ons, using our 3 button switches, and HEL performance master cylinders. We’ve fabricated a set of custom foot peg hangers for the rearsets and a modern and clean upholstery job by Timeless autotrim finishes out the rider triangle.

Our colour scheme was pretty open ended, Ryan likes the style we have on our bikes so the conversation was easy, we threw a few ideas around and landed on a nostalgic BMW M colour way.

As the entire body was aluminium we’ve integrated a strip of brushed aluminium into the paint design offsetting the stripes against an Icy white. Colourfuel has laid down the paint for us and we were stoked as we unboxed the parts for final assembly.

Once together the bike was sent for run in and tune with Dynomite Moto before we got out for our test rides. The bike holds a definite street presence, but is too large and cumbersome for my liking, although it does sound epic cruising down the road.