• On the KDM

    This bike has a long history. It started its life in 1985 as a KTM GS500 enduro dirtbike equipped with an air cooled 500cc rotax four stroke engine. I bought this bike when it was allready old and crappy with the intention to turn it into something like a supermotard. We're talking 1996 here, in those days the hype of the motards was just about to start hapening with some races and demo's in the Netherlands.

    Not hindered by much knowledge of the matter, I started to work on it. At my workplace, I had access to a lathe, a mill and welding equipment and the metalworking skills I had learned in school were helpful too. The desired properties of the new bike were: awesome brakes, road tires, light weight, quick handling and good looks.

    Quickly, I went out and purchased all the parts I thought I would need. First in went the wheels. Kawa ZZR wheels and brakes were available from some guy's racer project so I bought those. It wasn't easy to get them to fit. The chain was on the other side, therefore the rearwheel was flipped over. In order to get the chain aligned with the front sprocket, the chainwheel had to move 11mm closer to the heart of the wheel. So did the brake disk. Some bushes and a caliper bracket were added and the rearwheel was sorted.

    The front wheel was easier to mount. Two adaptors were made from billet alu to fit the calipers. Easypeasy, untill.... I sat on the bike and found out that the brake disks could hit the outer tubes of the front fork when riding over a bump. I went to WP Benelux to get this solved, and the guys there realy helped me out. They added 2 bushes in the fork that limited the stroke of the unit. As well an a set of stiffer springs. It resulted in a much stiffer fork, with 120mm in stead of 270mm of travel. A bit of viscous damper oil helped to give the front a real sportbike like suspension.

    Many parts I made from solid aluminium, like the rear sets, brake parts, mudguard brackets and more. Some of the parts had to be made several times because of a change in design, or because of failure in the real world.

    The seat is a replica ducati 916 glassfibre unit, and it is hinged in the rear to give access to the space underneath. After mounting this one, I went looking for a tank. Making my own alumium tank was tried and forgotten: too difficult. Steel was much easier for me to work with. I loaded the bike on a trailer, went to the nearest bike scrapyard and tried to find a matching tank. From all the tanks there, I found one of an old chopper to be the best base for me to work with. Back home, I took a black magic marker and followed the curves of my own knees on the side of the tank. I took my friend the angle grinder and cut away the parts where my knees would touch the tank. I formed the 1,5mm thick sheetmetal into the desired shape using hammers, steel balls and rings and lots of elbow grease. The pieces were welded together using the new TIG machine from work. Cool to see the lines of the seatunit continue in the tank isn't it? And cool it is that my long legs finally fit in the cavities of a fueltank. Patrick came to help often, and lots of epoxy filler was used to smoothen the surface. Finally, a local paintshop did a really good job and made it look 'real'.

    It started to be what I wanted it to be. Only the Rotax engine didn't want to cooperate. This is where KTM got their nickname “kick ten minutes” from. I made some money and decided to look for a new engine. I found a new ktm 640LC4 watercooled 4stroke that was an unused spare engine for a Paris Dakar team. Cool, this will be it. Another set of challenges apeared: mounting points, kickstarter, radiators, ah well nothing too complicated. After a while it worked. Now it had much more power and an engine that would start in one kick.

    With 10 things still to be done , the project got halted for several reasons. Different job, no more tools, new house, all those things. Every year I looked at it and sometimes had the guts to do something but in general it stayed in this 'allmost finished' state until 2009. Then, I took the bike for a spin and was unsatisfied with the handling. It handled like a Harley with 27 degrees of rake angle and lots of trail. This had to be addressed. Looking at the frame, I made a plan to cut out a wedge shape just behind the head stock and weld it all back together to get a much steeper rake angle. Then Patrick and I looked at the long front fork legs, and all the empty space underneath the head stock. This space was once needed for the long travel of the oiginal 19” front wheel. Now, with a smaller wheel and limited travel of the fork, it was useless. The idea came to mind to lower the front of the bike by sliding the fork tubes through the triple clamps. A trick that I had once applied to a guzzi. Only difference: on the guzzi it was 15mm, and on this KDM, a stunning 152 mm. (for americans: approximately 6”) . What could possibly go wrong? So we did it. This had a dramatic effect. The rake angle changed to 21 degrees, and the trail decreased to 65mm. Way to radical numers one would say, but the proof of the pudding, as allways, is in the eating and the first testride put a big smile on my face! This is how i wanted the handling to be: quick as a fox. With lowering the front, half of the total mass moved 152mm down as well, and the bending length of the fork tubes is much shorter now, making them stiffer. It all helped to improve the handling a lot.

    Again some time went by, and then in 2011, I got myself a proper workshop by my office. First thing i did was to bring in the KDM, and finish all the little jobs there were still to be done. The radiators got a new place under the seat, the muffler was changed for a quieter one and all the vibrating parts were mounted properly. By the end of 2011, it was all completed and this bike is now one of my arsenal.

    Each time I ride it, I grin...