Karlsen Racing KDF200 - Exclusive Test - Dirt Rider Magazine

It all started with a road trip. Back in June of 2009, Journeyman racer Matt Karlsen was watching the scenery fly by on his drive home from the EnduroCross season opener in Las Vegas when he decided to build an off-road bike. Just like that. Whether this wild idea was created by Matt's tired brain just to keep him awake or not is up for debate, but either way the thought consumed Matt's brain for the duration of the drive. By the time he pulled into his driveway in Denver almost 12 hours later, Karlsen had a plan. He headed straight out to his shop and started tinkering, and four months later emerged with the bike of his dreams.Now would be a good time to mention that Matt Karlsen is neither, by trade, a fabricator, nor is he a welder, engineer, architect or designer. Karlsen is a racer, and a pretty fast one at that. Be it at the Outdoor Nationals, EnduroCross, World Vet Championship or WORCS, it's not uncommon to see #940 roosting around the track in a respectable qualifying position. He's also an accomplished Triathlete, and has experience testing for one of the big manufacturers. So what made Matt decide to try his hand at bike building? "I figured that my dream EnduroCross bike didn't exist, so I just figured I'd build it myself. I really wanted something that was as light as a 250cc two-stroke, but without the 250cc hit that makes the bike sketchy on slick stuff, and with more power than a 125cc engine," Karlsen explains. "I figured that a KDX200 would be perfect, except the stock bike is about 250 lbs, really long and tall and the suspension is outdated. Since the stock KDX isn't anywhere near where I need it and nobody makes a modern day version of the bike, I decided to build my own."The first step was to pick up a 2004 KXF250 with a recently exploded motor. "A buddy sold me the blown up KXF250 dirt cheap," recalls Matt, "So once I got that I stripped the trashed motor down and sold the cases, crank, radiators and some other parts on eBay-that's actually how I funded most of the project!" With cash in hand, Karlsen then purchased a '94 KDX200 engine (again on eBay) and completely rebuilt it using the leftover money from the four-stroke parts.His next challenge was to mate the KDX motor with the 250F frame. Since the finished bike would be intended for EnduroCross applications only with no big jumps or landings, Matt chose to go with a stressed member frame, meaning that the engine is a supporting part of the frame. Karlsen spent several long nights in the garage measuring, cutting, welding and experimenting with the various components, and after some time was finally able to find a configuration that worked. Karlsen then recruited the help of his pal Larry Leavitt at LSE to finish some of the welds, and with that the bike was one giant step closer to being rideable. "One lifesaver is that I was able to mate up the carburetor in the original 250F air boot," says Karlsen of the process, "But the exhaust system was tricky. I got a new KDX pipe from FMF and went to work cutting and angling it to make it fit in the new frame. I had to cut, angle and weld a bunch of 45-degree angles to bring it back down underneath the shock reservoir like it should. It took some time but it finally lay in there nicely."With the 200cc engine fresh and plugged into the new chassis, Karlsen turned his attention to the machine's intended purpose: EnduroCross. "The whole thing in building this bike was to try to make it bulletproof," Matt explains. "I didn't want to be able to fall over and break the radiator open or rip the water pump off, so I decided to put the radiator between the frame so there was absolutely no way to break it. I also took the water pump off, block-plated the stock one and put an electric pump underneath the radiator so that it circulates at all times. It took some time but I made the stock lighting coil power the water pump and a small fan on the radiator. I ran a small temp sensor on the cylinder to make sure it wasn't overheating."In cradling the radiator between the frame spars, Karlsen effectively kicked the gas tank out of its stock spot. "I didn't have any place to put the gas tank, so out of necessity I built a two-quart fuel cell that sits underneath the seat and on top of the air filter. To do this, I took some sheet steel and hand built what I needed. It only holds two quarts, but that's plenty for an EnduroCross main event. To finish that part I took a Sawzall to the stock gas tank because I only needed the top half of it, so it looked like a normal bike." To complete the machine, Karlsen installed his trusty Flexx handlebars and Pro Moto Billet hand guards, as well as new graphics, tires and a little suspension work.It all started with a road trip. Back in June of 2009, Journeyman racer Matt Karlsen was watching the scenery fly by on his drive home from the EnduroCross season opener in Las Vegas when he decided to build an off-road bike. Just like that. Whether this wild idea was created by Matt's tired brain just to keep him awake or not is up for debate, but either way the thought consumed Matt's brain for the duration of the drive. By the time he pulled into his driveway in Denver almost 12 hours later, Karlsen had a plan. He headed straight out to his shop and started tinkering, and four months later emerged with the bike of his dreams.Now would be a good time to mention that Matt Karlsen is neither, by trade, a fabricator, nor is he a welder, engineer, architect or designer. Karlsen is a racer, and a pretty fast one at that. Be it at the Outdoor Nationals, EnduroCross, World Vet Championship or WORCS, it's not uncommon to see #940 roosting around the track in a respectable qualifying position. He's also an accomplished Triathlete, and has experience testing for one of the big manufacturers. So what made Matt decide to try his hand at bike building? "I figured that my dream EnduroCross bike didn't exist, so I just figured I'd build it myself. I really wanted something that was as light as a 250cc two-stroke, but without the 250cc hit that makes the bike sketchy on slick stuff, and with more power than a 125cc engine," Karlsen explains. "I figured that a KDX200 would be perfect, except the stock bike is about 250 lbs, really long and tall and the suspension is outdated. Since the stock KDX isn't anywhere near where I need it and nobody makes a modern day version of the bike, I decided to build my own."The first step was to pick up a 2004 KXF250 with a recently exploded motor. "A buddy sold me the blown up KXF250 dirt cheap," recalls Matt, "So once I got that I stripped the trashed motor down and sold the cases, crank, radiators and some other parts on eBay-that's actually how I funded most of the project!" With cash in hand, Karlsen then purchased a '94 KDX200 engine (again on eBay) and completely rebuilt it using the leftover money from the four-stroke parts.His next challenge was to mate the KDX motor with the 250F frame. Since the finished bike would be intended for EnduroCross applications only with no big jumps or landings, Matt chose to go with a stressed member frame, meaning that the engine is a supporting part of the frame. Karlsen spent several long nights in the garage measuring, cutting, welding and experimenting with the various components, and after some time was finally able to find a configuration that worked. Karlsen then recruited the help of his pal Larry Leavitt at LSE to finish some of the welds, and with that the bike was one giant step closer to being rideable. "One lifesaver is that I was able to mate up the carburetor in the original 250F air boot," says Karlsen of the process, "But the exhaust system was tricky. I got a new KDX pipe from FMF and went to work cutting and angling it to make it fit in the new frame. I had to cut, angle and weld a bunch of 45-degree angles to bring it back down underneath the shock reservoir like it should. It took some time but it finally lay in there nicely."With the 200cc engine fresh and plugged into the new chassis, Karlsen turned his attention to the machine's intended purpose: EnduroCross. "The whole thing in building this bike was to try to make it bulletproof," Matt explains. "I didn't want to be able to fall over and break the radiator open or rip the water pump off, so I decided to put the radiator between the frame so there was absolutely no way to break it. I also took the water pump off, block-plated the stock one and put an electric pump underneath the radiator so that it circulates at all times. It took some time but I made the stock lighting coil power the water pump and a small fan on the radiator. I ran a small temp sensor on the cylinder to make sure it wasn't overheating."In cradling the radiator between the frame spars, Karlsen effectively kicked the gas tank out of its stock spot. "I didn't have any place to put the gas tank, so out of necessity I built a two-quart fuel cell that sits underneath the seat and on top of the air filter. To do this, I took some sheet steel and hand built what I needed. It only holds two quarts, but that's plenty for an EnduroCross main event. To finish that part I took a Sawzall to the stock gas tank because I only needed the top half of it, so it looked like a normal bike." To complete the machine, Karlsen installed his trusty Flexx handlebars and Pro Moto Billet hand guards, as well as new graphics, tires and a little suspension work.

After some testing and a few gearing changes, Karlsen loaded up his newly-created "KDF 200" and headed to the next race on the EnduroCross series. "Everybody was pretty stoked to see the new bike, but a lot of people were concerned about the start, thinking that it didn't have enough power to get the holeshot," Matt said. "I was a little worried about that too, but I got two holeshots the very first time I raced the KDF! If you get a jump out of the gate it tracks really well and doesn't spin the tire at all. As for the rest of the track, the bike did exactly what I wanted it to. It feels really light because it doesn't have the radiators sticking out of the sides and it doesn't have the gas tank way up high. With the gas tank being behind you and the radiators being centered, it's more like a trials bike than an MX bike. It also seems that Larry and I got the frame geometry right, because the whole package is really well balanced. And when it's completely fueled up and ready to ride, the KDF only weighs 218 lbs. We shaved quite a few pounds off of the stock KDX!"To test Karlsen's performance claims, we hopped on the KDF and took a few laps around the EX track to see how the bike stood up. Without a doubt, the machine feels extremely light, especially in the front end. This makes it flickable like a 125 and easy to pop over obstacles, yet the engine maintains excellent traction everywhere while still producing a great amount of torque. The power rolls on well and is useable off the bottom, and when the revs come on it really starts to go and will just take off. First gear isn't all that useable because it is so low, so naturally we found that the bike was easier to ride in second. The suspension was tuned to a great enduro setting that allowed it to ride fairly deep in the stroke and corner super well as a result. Both ends could have used more bottoming resistance, but then again the bike wasn't designed for hard hits. Balance-wise, the bike certainly had the trials-like, low center of gravity feel that Karlsen was shooting for, making it easy to hop into and crawl over-rather than through-tricky rock sections.Of course, the bike isn't without a few disadvantages, all of which Karlsen is quick to point out. "Because of the design, you have to remove the seat to refuel the bike, which occurs every 10-15 laps on the track. I hate small gas spouts and this one tops them all! Also, you have to remove the side panel and seat to turn the gas on, and the seat itself is pretty harsh because there's only about an inch of foam due to the extra room that the tank took up. But by far the biggest disadvantage is the pipe: That thing is so custom, if I smash it at the track my weekend is done."All things considered, the KDF 200 is an impressive, EnduroCross-capable machine that is certainly competitive with anything else on the line, but the real magic of this bike is that it was hand built by a privateer in his own garage. Even after an estimated 60 hours in the garage and $500 in miscellaneous parts and welding supplies, Karlsen is quick to encourage his fellow riders and garage-based tinkerers to pursue their own dream projects. "If you have something like this that you'd like to do, go for it! The biggest thing is just plan out your idea and make sure that you are building the bike that you want to build. Structurally, if you're going to be doing big jumps and stuff then make sure that your frame is 100% spot-on because if you're doing big triples you don't want it to break on you. And also, get some opinions, go to some fab shops and talk to some people who have more experience than you. If you put a little bit of time into talking to people and putting your idea on paper first, it helps a lot."In a bittersweet turn of events, Karlsen was only able to compete on the KDF 200 for two races before signing with Coyote Motorsports to ride Yamaha YZ250 two-strokes next year. This means that the project bike will be parked indefinitely, and since Matt has no interest in building bikes for a living-he claims to not have the patience-this may be the last creation that we see from Karlsen. However, that doesn't mean that the bike's future is covered in dust. "I put so much work into the KDF, it's tough to put a price on it," Karlsen muses. "But it definitely could be bought. If anyone wanted to go to www.karlsenracing.com and make me an offer, I'd easily part ways with it in exchange for enough money to buy a new 250cc two-stroke, a gas card with a few hundred bucks on it and a well maintained Sprinter van!"A Sprinter van. Perfect. What better place to watch that white line drone by and think up yet another crazy project?

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