Cycle News - Archive Issues - 1990's

bustion Chamber (RFVC), which use large 33mm intake valves and 29mm exhaust valves. The XR400 en.gine develops its maximum power at 7500 rpm, and maximum torque at 6000 rpm. A gear-driven counter balancer reduces the amount of vibration emitted from the motor, and an automatic camshaft-integrated decompression system is designed to make starting - hot or cold '- easy. When the kicks tarter is 'swung through its stroke, one of the exhaust valves is automatically opened, making it easier to bring the engine to life. At 600 rpm, a centrifugal device disables the decompression system, allowing normal operation. In addition to the automatic system, a manual decompression system is incorporated into the design, and is actuated by a small handlebar-mounted lever. One of. the trickest features of the new motor is a quick-change clutch cover. Long incorporated on Honda's CR line of motocross bikes, the removable clutch cover makes it possible to replace clutch plates without removing the entire side crankcase cover. As a whole, the dry sump motor is quite light and compact, weighing only 84.8 pounds. For comparison's sake, the XR600 engine weighs 100.1 pounds, and is four inches wider and two inches taller. To keep things running cool, a large-capacity oil cooler is mounted on the frame's headpipe. A Keihin PD36 carburetor was developed especially for the 400 and handles the air/fuel mixture duties, while exhaust fumes ~re expelled through a two-into-one exhaust system. At the end of the head pipes is a modern-looking muffler, which is a far cry from the boat anchor that graces the XR6OO. Instead of the heavy, odd-shaped chunks of steel that come standard on most production four-stroke motorcycles, the XR400 has a racy, cylindrical unit that boasts a mesh·type spark arrestor. Of course, a baffle comes standard in order to keep the bike quiet, but may be removed with a few twists of a wrench. Chassis-wise, an all-new semi-double cradle frame houses the new motor. A combination of round and square tubing is used, and unlike the XR600 frame, the XR400 chassis combines the swingarm pivot with the rear motor mount. Incorporating such a design allows for a more compact design, as well as greater rigidity and less vibration. Oil is stored and cooled in the frame's backbone tube and horizontal bracing tube, the front downtube and large gusseting area behind the head pipe. Oil capacity is 2.3 quarts. Another hint of CR bike influence is found in the form of a removable subframe. The design allows for easier service maintenance of the air box and shock areas, as well as less expensive replacement costs, should the frame become bent in a crash. An all-new 43mm conventional Showa cartridge fork graces the front end. The new design is similar to that used on Honda's CBR900RR road race bike - the lower slider tubes aren't the traditional one-piece cast units, but instead are two-pieces bonded together. The slider tubes themselves are made of extruded aluminum, and tRe end caps are of cast aluminum. The new design allows for less underhang below the front axle - eliminating the complaint that most upside-down fork fans have with conventional units. The design is claimed to be more rigid, and is complimented by ~ double pinch-bolt axle-holder design. Past XR axles have threaded into the left fork tube, with the right side pinched into place. The new design incorporates a steel collar on the left side (Above) The all-new 397cc engine produces an Impressive amount of power for s mid-sized four-stroke. (Above right) Conventional Showa forks grace the front of the XR. The new legs borrrow technology originally developed for the CBR900RR road race bike. (Below) New, modem-looking plastic completes the bike. An aftermarket-style muffler sl,-nces, the beast, and Is light, to boot. The exhaust note Is extremely quiet with the baffle Installed, but t~ bike snarls with suthorlty without the restrlctor. fendeikeeps the mud out ~f the rider's face. The fuel tank stores the bulk of its capacity down low, helping the bike to maintain a low center of gravity. The grey airbox blends in with the side panels. No tools are needed to service the air filter, as the left side of the airbox is easily opened with the twist of three Dzus fasteners. The cover is fastened to the rest of the airbox with hinges, and there are no loose bolts or other pieces to be lost while servicing the air filter.' The seat also blends in well with the rest of the bike, and the two-tone seat cover boasts dual-density vinyl. The black area near the front of the seat is thicker than the rest, and is designed to hold up to the abuse of riders with knee braces. TREE BASHIN' Riders who don't know the "secret" technique needed to start a big fourstroke engine are usually left gasping for air on the side of the trail, but no such dilemmas will face XR400 owners. The bike is a breeze to start - finding top dead which the axle threads into, but the collar is cinched down by a pincll-bolt design as well. Thus, both sides of the axle are pinched, resulting in greater rigidity and improved steering response. The forks offer 18 compression-damping adjustments, and 12 rebound-damping adjustments. A full 11 inches of wheel travel is yielded by the legs. A piggyback-reservoir Showa shock gobbles up the bumps in the back, and offers 16 compression-damping adjustments and 16 rebound-damping adjustments. A Pro' Link linkage system connects the shock to the large-section aluminum swingarm. Rear travel is 11.8 inches. The entire brake system is ,the same as those found on the Honda CR line. That said, little else needs to be explained about the binders, as CR brakes are undoubtedly the industry standard. All-new plastic body work gives the XR400 a modern look. The rear fender/side panel junction is smooth and easy on the eyes, and a stylish new front Bit$:·and· pieces~· .. . " . '. . Mayb.a 'it~as our tester's 'fauit, bl!t' while' try·ing to kick st8rt the .bike, .the footp8Q repE1a,t-. edly,slamme,cI irito.hisshin .when thE! lever, went through It's fulf stroke. In ,addition, there ' " were. several ,times. Vihen the liick-sUirt lever' 'g0t stuck at the ,bottom of ilS stroke between ·the'footpeg br:acket'and. ihe f.ranie., ." :: , Stalllt)e bike?, 'If. you're lucky and,ther~'s a.hill . around.. simply pulling:in the ITl1!nual-d~m pression'lever ar)d rol,ling downh,ill will yi!lld a· surefire. bump ,start, ev.ery tilJ1e. Milnually" ·kick:starting tbe· bike whi,le .it.was in gear, was difticult: ' .., . ' .. .The stock hsnd' guard!! hav~ a .racy desig'1' 'and'arl!, fairly st.ton~, considering .that .they . .... . . . ' . '. don'tconilliet with the outslde·of.the handle-' The. new rear~fendar/~)de-J)snel de.slgn IS 'ba~ ir) Barll·.Bu~er fashlpn: During oiir' test" . exceUenl. The smooth hne.s of the new. plastic. 'We' made conta~t with several tree~ - a ,few at.' va~lts the XR hne .'nto the ~Os,.l;lnd. mak~s. '. sp,eed , anQ the stock guards ~ept.our' knuck-. .the older Xfl600 plece.$ look ancient arid out-.. leS intaCt. . '.. . dat,!d. rluring' a photo.~~oot, th~ clutch overheated' . ')lt6 ~dJust8ble .eompreBlilo'; an!l'febouind' and'became extremely grabbl:' after' it was. damping 0)1 tI1e fork and.shoq\< offer a. w de over-abUsed and·slipp9(j.repllatellly 'in a tight'. vaTleW of. opllOns. .For yoU .rac!!l~-typ~s ~ut 'seCtion of the 'woO

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