Soul-stirring in-line 6-cylinder engine ignites the
passion of two customizing legends




Kenji Nagai opened his workshop in 1990. While building custom machines he also turned his hand to developing original parts. He has won numerous awards at custom bike shows in Japan, and in the latter half of the noughties also became actively involved in shows in the US and Europe. He has received many Best of Show awards at these overseas events, too. Featured in custom motorcycle magazines around the world, Kenji constantly attracts interest in his new creations. Recently, he opened Ken’s Factory USA and is busy launching parts sales as an original brand in the US and Europe. His machined aluminum parts are widely known and respected for their high quality and exquisite taste.

Award Record
  • ・Yokohama Hot Rod Custom Show (Japan)/Best of Show
  • ・Cool Breaker (Japan)/Best of Show
  • ・LA Calendar Show (USA)/Best of Show
  • ・Las Vegas BikeFest (USA)/Best of Show
  • ・Custom Bike Show (Germany)/Best of Show
  • ・Verona Motorbike Expo(Italy)/ Best Of Show

and many more...

Keiji Kawakita

Keiji Kawakita opened HOT-DOCK CUSTOM CYCLES in 1984, where he set about customizing Harley-Davidson machines, many of which he exhibited at custom motorcycle shows. He has also been active in developing original custom parts. At the time he opened his workshop, he became involved in drag racing and also entered road races on single cylinder and twin cylinder bikes that were popular in Japan at the time. In addition to building custom machines, Ken manufactures and sells many high-quality/high-performance parts for use on the race circuit. He also built an original bike equipped with a V-twin four-valve engine that he designed himself. In 2008, he competed with the world’s finest at the “World’s Biggest Build Off”, a custom bike show celebrating the 50th anniversary of S&S Cycle, an American after-market specialist in the Harley-Davidson sector.

Award Record
  • ・WORLD BUILD OFF/World champion (2008)
  • ・COOL- BREAKER/Sponsorship

and many more...


Instead of making a luxury tourer even more comfortable, I made it bit edgier. For me, customizing is part of life.


This was the first time I’d tackled a BMW, and I was reminded that the theories I’d amassed to date about customization would not work with this machine. So for this project, instead of going straight to work, I spent a long time in planning and thinking things through. Once I understood the complex wiring construction, I felt I could move on to the next thing.

At first I had a bagger style in mind that grew out of the tourer image. But simply transforming a tourer into a bagger was a bit too obvious a choice. So I thought of a different approach. I settled on the digger style. The long, thin digger style would make the in-line 6 cylinder engine look even more prominent.

To realize this design, I cut the front end of the frame and built it anew. I installed our own brand of aluminum girder forks. I measured the dimensions with the bike in its standard state, and determined new dimensions around the neck using the cut off steering head. I changed the 17” wheels front and back to 23” front and 20” rear, and gave the outer packaging an extremely simple finish.

By a continuous process of trial and error, I made more mistakes than I’ve ever made before. So I didn’t have much fun during the building. But with the completed machine in front of me, I got a great sense of relief and was able to look back on an interesting project. Working on a new bike brings many new discoveries, which I intend to make use of in future projects.

Customizing is an integral part of my life. Even when I’m taking a bath, playing around or having a drink, I still keep getting ideas about customizing and components. So as not to forget, I also keep memos in my mobile phone. But life sometimes takes over, and I forget about the memos (laughs). It was the same with this project. As a result, I adopted a playful approach to the K 1600 GTL, and produced something way different from the standard machine, in a way that I think satisfied expectations, too.

I just dived straight in without doing a single image sketch. Some things turn out better than you imagined.
That’s what’s fascinating about customizing, what gives it depth.


We arrange the parts we fit and adjust the profile of the machine to get the customization we are aiming for. Good looks and riding fun are a result of maximizing the use of minimal equipment. But I thought the K 1600 GTL was at the opposite end of the scale from this. So I fretted quite a bit even after taking the body apart. But I set to work, and when the front end began to take shape, the image I had of the bike suddenly grew.

In fact, about a year previously, I found an old photograph of the cockpit of a convertible that looked like something from the near future, and I got the idea of making a bike that had that kind of atmospheric feel. Looking at the front forks and Duolever suspension, I thought I could do this with the K 1600 GTL.

But the actual work was long and hard, a tough job to handle. In the middle of building I still didn’t have a clear picture of the completed work. Even when I finished, I still wasn’t really sure whether the work was complete. But that’s the thing about customizing, isn’t it.

The suspension and frame I left as standard, but the exterior parts are all hand made. I made a framework for the exterior with aluminum pipe, fixed aluminum panels to this front and back and then proceeded with finishing. The gauges I set in the exterior packaging were dummies, but I changed the positions of panels and needles to match up with adjacent parts. Parts other than the packaging are all given an aging paint treatment.

For a while after I was crowned champion at the “World’s Biggest Build-Off” in 2008, I found myself bereft of ideas about customization. I felt a bit used up, and thought about leaving it to the younger generation. But the R nineT Custom Project got underway around that time, and seeing the younger builders enthusiastically getting stuck into it was maybe the stimulus I needed. Then, when I saw the K 1600-based custom machine by the Belgian builder, Krugger, I was blown away. The custom scene is a world of freedom. I was also keenly aware of changes on the bike scene. So for this project, I wanted to make a bike that shouted out to all the people who'd given me the renewed incentive. A bit later, I noticed how tough it was to build a custom machine based on the K 1600 (laughs).

But the project was enjoyable nonetheless. I was getting up early, already thinking about an area I was going to work on, and this seemed to be happening naturally, every morning. There were a lot constraints and trouble spots, but these were more than compensated for by the fun of it. I really haven’t felt like that in a long time.


Powered by BMW’s traditional silky six.
The K 1600 GTL Tourer par excellence that delivers complete freedom.

K 1600 GTL

K 1600 GTL
K 1600 GTL