This site will look much better in a browser that supports web standards. Your browser does not support web standards and therefore our content will be visible but perhaps not beautiful. Go on... upgrade.. it won't hurt!
|
The Honda XR650R: The King of Baja
Enormous pressure was put on Honda when the new Yamaha four stroke came out. But the folks at Research and Development would not be rushed. Many different prototypes were sent to the US for testing, and all of them were sent back. Bruce Ogilvie, a long time Baja racer, knew exactly what was needed, and the stuff they were sending him from Japan, wasn't it. Finally, the new Honda XR 650 arrived. And it arrived with a flourish! Johnny Campbell took a lightly modified 650 and opened a can of whip-ass on everybody else at the Baja 1000. And what finished right behind Johnny? Why, another XR 650! So it was with a great deal of interest that the staff of ORC met with Honda, and tested the bike where it seems to work best: right here in Baja. FIRST OFF, THE BAD NEWS If you buy a brand new water-cooled XR 650R, chances are you are going to be mightily disappointed if you ride the thing stock. Bruce Ogilvie brought one of the "pure stock" bikes with him, exactly the way it will sell off the showroom floor. The ORC testers were the first to ever sling a leg over this bike. In all the magazine tests you read in the very near future, the testers DID NOT RIDE THIS BIKE! All of them rode the "modified" version of the XR650R only. The stock bike is strangled, on purpose. In order to meet strict emission requirements, the bike has a horribly restrictive air inlet, a tiny opening in the muffler/spark arrestor and a reducer in the carb manifold that's half the size it should be. It's amazing that the bike would even get out of its own way with this much crap going on. Ridden like this, the XR650R is so quiet you can hear the chain slap on the sprockets and even hear normal engine noise from chains and the valve train. The engine puts out 43 horsepower at 6750 rpm with all the emissions junk installed. With the restrictions removed (and properly jetted), the bike comes alive and pumps out 27 percent more horsepower, all the way up to 55 strong ponies, about the same as Campbell's race bike from the 1998 Baja 1000. Let's be blunt: riding the stock bike is not very exciting. The power is good, with lots of low rpm grunt, and the mid-range will easily pull the upper gears early in the rpm range. But, in our opinion, Last year's stock XR600 was faster and more impressive through the gears. We're sure there are some riders who will leave the XR650R in stock trim. These same riders would probably be just as happy riding a five year old Suzuki DR 350. But if you have any hair on your chest at all, you will absolutely fall in love with the power of the "cleaned up/jetted" XR650. This thing rips! Power starts right at idle, churns into a monster mid-range, and even revs out like a road racer. If you want more power than this bike delivers, there are very few places on the face of this planet where you are going to be able to use it. TECH STUFF YOU MIGHT WANT TO KNOW This is the most powerful engine ever in a Honda XR; it's a liquid-cooled 649cc SOHC four- valve dry-sump engine. The single-backbone aluminum frame represents the next evolution in off-road aluminum chassis technology. Kayaba suspension components replace the old Showa units. The package provides a combination of comfort and plushness, with excellent control and performance. A 46mm front fork is matched to the 44mm fully adjustable long-stroke piggyback rear shock absorber. Optional competition parts increase horsepower and torque an incredible 27 percent! ENGINE
POWER A huge part of the XR600R's appeal has been the quality and quantity of its power. Still, XR owners have always figured more is better when it comes to horsepower. So, when the XR650R design process began, more horsepower was at the top of Honda R & D's shopping list. To meet power and durability goals, more displacement was a given. Testing various intermediary engine sizes revealed a 649cc single-overhead-cam four-valve single delivered the perfect balance of power, torque and toughness. Since more power means more heat, liquid cooling was a given as well, opening the door for all-new engine architecture from the cam cover down. Gone is Honda's familiar Radial Four Valve Combustion (RFVC) system, with valves splayed radially around the bore axis. The XR650R uses a lighter, simpler, more effective overhead camshaft system, above a flat combustion chamber that's fired by a single spark plug. Mixture from the 40mm Keihin carburetor enters via a pair of 37mm intake valves (up l mm from the 600), and exits through 32mm exhaust valves (also l mm over XR600R spec). These valves are controlled by a cam with more lift, overlap and duration than an XR600R's. Just below, the 650's Nikasil-lined aluminum cylinder moves closer to vertical than the old bike, creating more space for the twin aluminum radiators. This more upright engine position also shifts the crankshaft center closer to the front wheel to help optimize weight distribution. Both the l00mm bore and the 82.6mm stroke are enlarged from the XR600R specification. Despite a 3 millimeter increase in diameter, the XR650's three-ring piston is 10.6 grams lighter than an XR600 slug. An automatic XR400R-type adjuster makes sure there's never slack in the cam chain. A new closed-deck head construction creates a significantly stiffer cylinder and an improved head gasket seal, shaving 230 grams, by using four cylinder studs instead of the XR600's six. Cast from a new corrosion-resistant alloy that is 10 times stronger than previous alloys, a new CR-style magnesium cover provides easy access to the XR clutch. The newest XR's bottom end is tougher and more efficient. A gear-driven counterbalancer squelches the big single's endemic shaking and drives the engine's water pump from the right end of its shaft. Like the previous XR, the 650 engine is dry-sump, carrying its engine oil inside the frame in a space at the juncture of the cast-aluminum steering head and extruded-aluminum main downtube. Strategically placed partitions in the crankcases minimize power-robbing windage by keeping excess engine oil away from the crankshaft. Ignition componentry runs dry, rather than in an oil bath, as in the XR600 engine for the same reason. Also, the crankshaft cavity features a Honda first: a one-way reed valve that allows piston pressure to force excess oil into the transmission area. Working with Honda's cam-actuated automatic decompression system, a new reduction ratio in the kick start gear makes lighting the big XR's fire easier, by spinning the engine faster with each stroke of the kick lever |
||
|
|||
|
|||
|
|||
|
|||
|
Honda's big XR 600 has been around with minimal changes since
1982 (it was a 500 cc bike back then), so by the time the XR650R arrived, the change was long over due.
