The current backyard mini craze began with Honda XR80/100R engines being transplanted into two-stroke 80cc motocross chassis. As amazing as it seems, there are at least two good reasons to replace a modern, powerful, reliable 85cc two-stroke engine with a larger, heavier and somewhat-antiquated four-stroke mill. The first is that adults racing or play-racing on smallish four-strokes are having more fun than humans should be allowed to have, and how do you put a price tag on that much fun and recapturing your youth? The second is that advanced riders who have outgrown the crude stock suspension of their entry-level trail machines now have options other than switching to race-bred two-strokes.We'll concede that most modified four-stroke minicycles end up at backyard home-brewed tracks, but there are also organized races. For years, there was an understood class limit of 150cc for the bikes that used two-stroke chassis. That rule made sense since the outer limit for the Honda XR100R engine was 150cc. Now, with a lot more engine options and combinations, the rules—for events sophisticated enough to have them—usually say any air-cooled, two-valve engine is fair game. Most conversions are based on Yamaha TT-R125 and Honda CRF150F engines, but the cheaper and more-plentiful XR200R power plant recommended by Dave Miller of Dave Miller Concepts (DMC) is a known quantity with great aftermarket support.So how did we end up building our own XR200R-powered mini racer? As part of a collaboration between eBay and Primedia, 10 magazines were chosen to build eBay-financed project vehicles. In the end, all 10 will be judged by the public; a winner will be selected; and eventually the projects will be auctioned off, with the proceeds going to a charity that refurbishes donated vehicles for needy families. The choice of the particular project was left up to us, and eBay gave us a budget of $8000 with which to work. The machine and parts chosen were to be purchased on the auction site whenever possible.
The car, truck and streetbike magazines could just do their normal projects with parts from eBay, but for Dirt Rider, that plan didn't make sense. There are precious few used hop-up parts that are worth much, so we opted not to do as the other books did, which was to buy a used car/truck/4WD/streetbike and fix it up. But a custom four-stroke mini is a perfect eBay project. The only way to build one is to begin with two perfectly good motorcycles and, after a lot of time and money, end up with only one and a pile of extra parts. The final requirement of the Primedia Editors Charity Challenge is to gather all of the vehicles at California Speedway in Fontana, California, where they will run down the dragstrip and on the skid pad. We probably won't be able to talk them into putting in some jumps or whoop sections, so we can't see how a full-grown (some say overgrown) adult is going to avoid looking like an idiot on a 16-horsepower minibike. Since actually trying to race with real hot rods would compound the problem, our plan is to attempt to wheelie the entire way.Despite the headline used here, there is no such bike as a Honda CRF200X, but there should be, and there is no good reason we can see why Honda (or any manufacturer) refuses to build one, except cost, as the retail price based on projected production volume makes its creation nonsensical. That's another reason we chose to build this bike. The vast majority of the bike shown here is straight production Honda. Honda builds not one but three engines that bolt right in this DMC-modified CR80/85R chassis: the CRF150F, the XR/XL200R and the CRF230F. The suspension, brakes, wheels and body parts are all stock CR80/85R fare. Our machine has a Thumper Racing 2mm-oversize big-bore kit with a Wiseco high-compression piston (still less than 200cc total), but the engine could easily have been left stock.The hand of the aftermarket is heavy in places, however. The DMC frame modifications require 42 laser-cut parts and brackets and 7 feet of chrome-moly tubing! The exhaust pipe and intake manifold are special limited-production items from DMC that are included in the frame kit's $1999 price.Locating a proper CR80R or 85R Expert donor bike was easy, but finding one cheap enough to justify the shipping wasn't. Finally, a clean 2001 showed up within driving distance, and we bid high enough to ensure we'd get it; but there weren't other bids, so we bought it for $1600 with the original tires still fitted and in good condition. It didn't come home with us, though; it went straight to DMC to have the frame modified. Beginning with a new frame (no numbers) rather than one with a clean title is too much of a paperwork nightmare. If you desire to start with a new frame, all states have a process in place that allows for frame changes. Buy a new frame, and then take it to the proper authority to have the official frame numbers stamped or riveted on. In The Golden State, the California Highway Patrol does the VIN inspection. You'll need to do the same thing after the new engine is installed, so if you have the engine to bring along at the same time, you will save a second trip.We got the completed frame kit and all the stock parts back from DMC before we were able to locate a suitable XR200R. We saw many at reasonable prices, but they were on the wrong side of the country and, again, the shipping costs made them undesirable. Then we spotted a clean 1990 owned and ridden by a woman (so less beat) but mostly parked for the last 10 years. The price of $1800 was more than we wanted to pay, but with shipping it would cost nearly the same for a much harder-used example.We pulled the engine and took off the top end to check it out. eBay allowed some donations to the project—within limits—but we were allowed to use things we had around. We remembered there was a shipping-damaged (a chipped fin) Thumper Racing 2mm-oversize XR200R cylinder and Wiseco high-compression piston stashed in the garage. We even had gaskets, so we were able to button the engine back up the same day. The carburetor was pretty gummed up from sitting, so we replaced the pilot and main jet and cleaned it up a bit. The tappet clearance was a bit loose, so we adjusted those, drained the oil and were ready to roll on.DMC engineered the frame well, and the engine and all the other parts fit fairly easily. Still, the bike didn't run correctly, and editor Jimmy Lewis properly diagnosed and remedied a plugged carburetor air passage.We had a few small issues to deal with once we rode the mini. It was very hard to kickstart, but the XR donor bike came with the original manual. It detailed adjusting the automatic decompressor cable, and once that was done, it started very easily. Also, the exhaust pipe is very close to the cable, so we insulated the pipe and the cable with a section cut from a high-temp spark-plug boot cover from Performance Automotive Warehouse. A radiator no longer supports the right-side shroud, and an aggressive rider could squeeze hard enough with his knees to push the tip of the shroud in far enough for it to interfere with the fork. We had bought some Works Connection frame guards on eBay, and they came with a radiator guard plate that we'd consigned to the spare parts bin. We dug it out and installed it between the tank mount and the lower shroud brace. Voil! No more problem. All that was left was to install the new graphics and fresh Bridgestone M401/402 tires and to make a quieter muffler/spark arrestor. We modified a used FMF spark arrestor for a Kawasaki KX250 to fit the DMC header. That made us spark- and sound-legal to ride off-road in California.Getting the air filter and its cage mounted takes some patience, but otherwise we are very happy with our bike so far. Small and light riders love it on the track or on the trail. It likes berms better than flat, slippery turns, but it corners well enough. It shines in fast sand washes and handles better through whoops than the stock CR80R did. Dirt Rider's Corey Neuer raced the eBay special at the infamous Langtown backyard minibike supercross. The bike grabbed the holeshot at every start and ended up second in the amateur class. Neuer is 5 feet 11 inches tall and weighs 160 pounds, and the bike worked fine for him; and it also worked for a 5-foot-3-inch, 120ish-pound female trail rider.Now if we could just come up with the money to buy it for ourselves.