Cycle News - Archive Issues - 1970's

E • ~ t C'I M ~ ..c e ~ o Z Honda XRIKawasaki KLX 250cc dirt duel Green matches red and thump-thump ahead By Tom Mueller Photos by Jack Wright and Mueller In recent years Big Brother has taken an Interest in the American motorcyclist in the form of the EPA. Emissions regulations get stricter by the year, and the effect of such regulations will have a direct bearing on competition machines. In the near future highly 14 refined two-stroke motors used in current enduro/trail mounts may b~ . a thing of the past. The only option available to manufacturers, if they wish to keep these bikes on the market, is a four-stroke engine - which will satisfy ever increasing emissions requirements. When the change occurs, many will probably feel they are being forced to ride something that has regressed from what it had been. But to others, the' thumpers wilt be a welcome addition to the dirt scene, When Yamaha introduced their TT500, the market was instantly there; Suzuki followed with their DR370 four-stroke effort, Big Red and Big Green seemed to feel it was time to put a serious production run of four-stroke competition machines on' the market and pick up on that segment of riders/buyers who are looking for a machine that you don't have to mix gas for. The way the two companies looked at the project and then developed it, however, came from two different..... resources that both had already tried, tested and secured. In 1978 Honda based its XR on the already proven XL machines, which are street/ trail bikes with all of the compromising extras. Some street orientations were removed and other enduro alterations added until the combination was right for the XR250 to grab a spot in the off-road market, Honda's work devoted to the XR was, for the most part, extensive, R and D people at the plant had already produced the successful MR enduro series, and the knowledge from that project, plus the highly competitive enduro market, left no doubt that their latest ,effort could be nothing short of serious, The XL engine went to the'shop and came out pushing four more horsepower, due in part to 30,5mm carburetor that replaced the XL's 28mm mixer. Retained from the XL powerplant was the overhead cam four-valve dual exhaust port head and twin pipe arrangement which allows for increased cooling of the valves and allowance for a sharper bend in the pipe without obstruction to air flow. Vibration reducing counterbalancers also remained in the XR package, aiding in a smoother engine that transfers less fatigue to the rider. The counterbalancers also allowed for less gusseting because of the lower vibration factor, resulting il1 a lighter frame. Though the motor was treated with a laissez-faire attitute to a certain degree, the rest of the XL received major alterations before the XR was formed. Exclusive Honda design clawaction tires replaced the road/trail units, the frame was altered, a different . swingarm was bolted on, heavier duty forks and shocks were added which increased the suspension travel .8 inch front and rear, a chain tensioner was included, a rear fender mount tool bag was added, an enduro oriented speedometer/odometer was put on, a different pipe was fabricated and an alternate lighting system using a smaller taillight and headlight/number place arrangement was installed. Retained was Honda's 23 inch front wheel which was designed to traverse terrain with greater ease than a 21 inch wheel, . staying on top of bumps and potholes instead of falling into them. Through all of Honda's steps on the way to the creation of the XR, more consideration could have been given the factor of weight. The XR weighs only 7.5 pounds less than a stock XL, which has signal lights and other road legal detailing. At a claimed 252.5 pounds dry, the XR isn't winning any 250cc enduro bike low weight contests. Asthetically the bike is in good shape, the best job possible having been done within the basiC limits of the XL's realm. If what is offered isn't enough, amends can be made through Honda's HPO--High Performallce Option Kit. The kit includes crankshaft, head, -cylinder, carb and exhaust pipe, but raises the displacement to 255cc-outside of some 250cc classes. The group of engineers at Kawasaki found a way to produce their fourstroke enduro bike without the effort Honda put into their mount. Instead of using their KL250 street/trail machine and working from it, Kawasaki took the engine from tl!at bike and mounted it in a KXI25 motocrosser, one of the companies most capable dirt bikes. The entire project required little modification. A CDI replaced the battery/points ·system of the KL motor,

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