CYCLE WORLD TEST
Yamaha has the distinction of being the first Japanese manufacturer to build an open class motocrosser that threatened the European makes' suprernacy. The 1980 YZ465 would outdrag, out-jump and out-brake all the others. Maico, the best in class until the YZ465 came along, countered with a fire-breathing 490 for '81 and regained the drag-race award. Yamaha liked the mostpotent open motocrosser image and so for '82 they too have a 490.
Making a 490 from the 465 was simple. Yamaha bored the 465 another 2mm. Stroke was unchanged, as were the flywheel and ignition. Porting was modified, but not radically. A new pipe completed the changes. Carburetion—a 38mm Mikuni—stayed the same but jetting required minor revision. Other changes were small things like a new head with a wider combustion chamber to accommodate the bigger piston, a new silencer and the addition of Yamaha’s YF.1S, commonly known as a boost bottle.
The engine’s bottom end uses the same cases as the 465 but the transmission has lost one gear. Four larger and stronger gears now fill the cavity previously occupied by five. Some really hard riders experienced transmission failures during ’80 and ’81 and the stronger four-speed is supposed to cure the problem. The wideratio four-speed eliminates first for all practical purposes. First gear on the fourspeed is 14.44:1 compared with 15.10 for last year's second. Top gear on the 490 is 6.87, taller than last year’s 5th at 7.19. These ratios applied to last year’s 465 would have made for difficult riding for all but top-level pros, but the bigger engine with its increased torque and pulling power hardly notices. Other parts of the engine: clutch, main bearings, reed cage and reeds go unchanged for '82. The intake tube is new. however. It is the same length and diameter, but it has a snout on top to hook up the boost bottle.
Although the frame has a new part number, only the back half is new. A large single front downtube, quick-dive top tube, heavily gusseted 28.5° steering head and double engine cradle tubes remain the same. The back half is different, to accept the new Monocross linkage. It looks like last year’s frame but an additional pivot shaft has been placed between the swing arm pivot and the seat rail tubes. This shaft holds aluminum linkage that adds a progressive leverage rate to the rear suspension. This linkage has also eliminated Yamaha’s triangulated swing arm. The new extruded aluminum arm looks similar to what the other guys have. >
YAMAHA YZ490J
Four Speeds and a Big Motor Aren't Quite Enough
The new rear suspension is much like the factory racers’ suspension used during the ’81 season. Where the old system relied on progressively wound and tapered wire springs for a rising rate, the new system uses a straight-wound spring and gets its progression from mechanical linkage. The linkage is aluminum and pivots in a combination of caged needle bearings and bushings. There are five pivot points. The three rear joints have grease fittings to ease maintenance, the front two don’t and require disassembly to lubricate. Why didn’t they put fittings on the front two? Yamaha spokesmen didn’t know.
Anyway, the aluminum-bodied shock is new. It’s 1mm larger in diameter, has a bigger remote reservoir and adjustable compression and rebound damping. Rebound damping has been tunable for a couple of years and still adjusts the same—at the rear of the shock, just in front of the rear wheel. Twenty-five choices are available with the twist of your wrist. Turning the adjuster in makes the rebound slower, turning it out makes it respond quicker. Compression damping isn’t as convenient. The adjuster is at the front of the shock, below the middle of the gas tank. Adjusting it to any of its 20 positions requires removing the tank or at least the tank screws and lifting the front of the tank. Then it can be reached with a long flat-blade screw driver. It adjusts like the rebound damping; all the way in is the most, all the way out is the least. Too bad the adjuster knob isn’t extended to the front edge of the gas tank where it could be easily reached. Naturally the shock is pressurized with nitrogen. Pressure is lowered to 114 psi standard with 140 psi as maximum and 100 psi minimum. As delivered the bike is set up for an average rider. Yamaha describes an average rider as being an intermediate who weighs 154 to 165 lb. They have a chart that explains about heavier and lighter riders and different surfaces like sand or hardpack and different rider abilities. Harder courses, heavier riders or better riders require an optional heavyduty spring. Softer courses like sand, or slower or lighter riders, require an optional light-duty spring. The springs are available from Yamaha dealers.
Forks once again have 43mm stanchion tubes, 11.8 in. of travel and aluminum lower legs. But they are completely new. The lower legs are aluminum tubes, not castings. The tubes have the bottom caps welded on and are stronger, lighter, and probably cheaper to make. Air caps are provided but Yamaha suggests no air pressure. Oil level can be adjusted and heavier and lighter springs are available. Triple clamps are aluminum with double pinch bolts and rubber
damped handlebar pedestals.
A new approach to a seat/tank is used on the ’82 Yamahas. Because everyone slides forward when cornering, Yamaha has extended the seat over the tank. The rear part of the tank is slightly dipped to accommodate the seat and a tongue and loop connect them. The narrow plastic tank holds 2.6 gal. of premix.
Plastic parts are mostly new with the front fender and square side plates being the most obvious. The front fender is nice and wide and does an excellent job of protecting the rider from mud. The air cleaner box is also new. The side cover is now separate from the side number plate and easily removed after extracting one screw.
Controls are normal good Yamaha stuff. The shift lever folds, the throttle is a straight-pull model, hand levers are dog-legged, cables are strong and have large housings, the rear brake pedal has a claw top and the grips are usable.
Wheels are unchanged. They have strong hubs, good spokes, aluminum rims, a double leading shoe front and single rear brake. Footpegs have aggressive tops and strong return springs. Missing from the ’82 YZs is a fold-up kick stand. Most racers, and the YZ490 is a fullblown race bike, prefer no stand to come down or fall off during competition. Dealers and people who use race bikes for purposes other than racing like stands. Yamaha does supply a prop stand that slips around the lower frame tubes for use at the dealership or in your garage. It can be bolted in place and will hold the bike up, although rather wobbly, without the bolt.
Starting the YZ490 is much like starting the other ’82 Japanese open motocrossers: painful. It’s a brute to kick and the lever bottoms against the footpeg. Adding insult to pain, it usually requires 10 to 12 kicks when cold and up to six when warm. Part of the problem is the amount of energy required to kick the engine over. Hardly anyone can boot the beast hard enough to start after the first four or five kicks. Then you might as well rest before attempting it again, or it’ll take 25 half hearted kicks, lots of cursing and a fresh (sorry) buddy to get it running.
Once running it almost becomes worth it. What a delightful engine! Not much vibration for an open bike and lots of smooth predictable power at any rpm. All of the 465’s low-end blubber is gone. First gear is quite high, as the gearing indicates, but the incredible torque lets the bike pull smartly away, front wheel in the air if too much throttle is dialed on. Shifting isn’t smooth, but it’s not really hard. Just more than ideal pressure is required. And it’s somewhat notchy until lots of miles are traveled. Transmission ratios are wider than they look on the
spec chart but the engine pulls with no hint of bog or flatness. Top speed is much higher than you’ll ever need for any motocross we’ve ridden but not enough for serious off-road racing. And gearing the bike up means first gear will get too high for really rough and steep hills. We did try a countershaft sprocket with one more tooth. Top speed was adequate and some steep hills could be climbed as long as an expert rider was aboard and no one got in the way. For off-road use you need five speeds. Last year’s five-speed transmission will fit. Total cost is around $425 according to Yamaha. We also got a price breakdown on making last year’s fivespeed YZ into a 490. That’s even more costly. The cylinder goes for $283.55, the head is $57.20, piston kit $57.20, rod bearing $5, boost bottle and hose and tube total $16, the pipe is $124.75 and the silencer $51.50 for a grand total of $623.50 plus tax and odds and ends.
It’s a bolt-on deal though. If you have a 1981 465 all set up for desert racing it might be a worthwhile way to go. And it won’t be a giant hassle trying to fit a larger tank. The seat will make a large tank swap hard on the ’82. And all of the parts aren’t completely necessary. The stock 465 cylinder can be bored to accept the 490 piston but it’ll get chancy if you have to go oversize from there. And the stock pipe can be modified to perform almost as well as the 490 pipe. The head can be turned out to the correct diameter on a metal lathe and you might adapt your old silencer. Going this route a 465 can become a 490 for around $90 plus labor for machining and welding. Doing it better, add $283 for the cylinder. Anything’s possible if you have a sick 465 and don’t want to lay out the price of a 490 and the problems of setting it up for offroad use. The YZ490 may be a pure motocross bike but many people (including Yamaha’s race team) have used open motocrossers for other things.
How the big YZ works as a motocross bike depends in large part on how well the suspension is dialed in. There are a lot of adjustments available on this bike. Besides simple spring preload changes, the damping can be varied on both compression and damping and fork fluid volumes and viscosity can be changed, as well as fork height. As it comes from the crate most adjustments are in the middle of their ranges and the bike is far better than any motocrosser that’s more than a couple of years old. Follow the instructions in the excellent owners manual and the YZ490 can be tuned into a much better machine.
Stock, the 490 compression damping is set six clicks out, rebound damping is nine clicks out. Yamaha recommends changing one setting at a time and two clicks each change. At the standard setting the back of the bike kicked badly>
over square holes. Setting the compression damping another two clicks out removed some of the kick and set 10 clicks out it was even better, but then it would bottom when ridden fast or off high jumps. Nine clicks and a little more spring preload worked best, with the rebound damping set 12 or 13 clicks out.
With these settings the 490 was closely dialed in for a variety of tracks. Damping adjustments didn’t have to be moved more than a click or two from track to track. Lowering the fork oil level a half inch improved fork compliance, reducing the harshness that occurred on landing from jumps.
All our test riders came to about the same conclusions. They loved the power, forks, controls, ability to slide forward on the long seat, brakes and solid feel the bike relays. Most didn’t like the rear suspension. In fact, most thought last year’s rear suspension was better! The suspension isn’t as supple on small bumps and it
kicks. Reducing the compression damping makes it smooth on small bumps and stops the kicking, but then it bottoms. Lever ratios for the ’82 system start at 2.826 and end at 1.843, which makes it a true rising rate, but it doesn’t rise much when compared with some other rear suspension systems. And we suspect last year’s YZ had more progression with its tapered wire spring.
The bike also has a generally big and clumsy feel about it. It’ll go through corners at a fast clip, and it doesn’t fight the rider or have a head of its own, but it takes muscle to turn it. And the extra rear linkage has added more weight high on the bike, which the YZs already have too much of with the shock placed so high. All this adds to the big, heavy, weight-ontop feel always present when riding the 490.
This bike proved the most troublesome YZ we’ve tested. Would you believe we went through five chains including the
stock one? We did. The first time it pitched itself the all-plastic chain guide went with it. And it wadded the chain into a pretzel-like mess. The second chain tore a piece from the case by the clutch arm, requiring heli-arc welding. The third chain again took out a chain guide. * We suspected the guide was breaking first and derailing the chain. After fabricating a metal and plastic guide from old Kawasaki parts and making sure everything lined up, we put on another chain and promptly pitched it. Chain number five bent the shift shaft and locked the trans-^ mission solid.
Some of the chains derailed in turns after slamming into berms, one went going over a jump with a turn in it, the last one pitched itself going over a small jump in a straight. After checking the suspension levers for looseness, pushing* and pulling on all of the parts, checking bolt torque, alignment of the various parts and pieces, we gave up and sent the
YAMAHA
YZ490J
$2349
bike back to Yamaha for a complete check.
Yamaha kept the bike for a couple of weeks and returned it with new cases and a new lower end. The last chain derailment had chipped some of the transmission gears and generally played havoc with the other internals.
When we asked about what was causing the problems on our 490 we learned the first 490s in this country had countershaft sprocket bearings with eight balls; later models have nine balls which spread loads better and add stability to the shaft. Additionally our bike’s axle position marks were 4 to 5 mm off. We don’t use swing arm marks when adjusting chains anyway. We sight down the chain, so that didn’t cause us any problem. The first few hundred bikes also had off-center chain guides, as did ours. That was evidently the start of our chain problems. And one of the chain derailments bent the rear axle. There’s a dealer up-
date concerning the early models with the eight-roller bearing and offset chain guide. If you have an early YZ490 check with your dealer.
Anyway, when the bike came back it was a different machine. Suspension was more compliant, less kick on squareedged holes, less muscle required in turns and generally more fun to ride. It still felt larger and heavier than other open motocrossers though. And it is. As an example, it’s 8 lb. heavier than Honda’s 1982 CR480. The new YZ490 feels 20 lb. heavier than any of its competitors.
Does that mean we don’t like it? Well, yes and no. The engine’s power is very European—smooth, predictable power with enough flywheel weight to keep wheel spin to a minimum, but light enough the engine doesn’t feel sluggish. Just right. Forks are good strong units that have the right amount of travel and perform well. The frame and swing arm are strong, don’t Hex and are nice to look
at. The new seat/tank unit is stylish and probably a forerunner to what the other guys will be doing next year. Wheels, tires, spokes, controls and general good quality accessories hooked to the bike make it worth the money. None of our testers thought the rear suspension matched, or came close to matching, the rear suspension of a Suzuki RM, Honda CR, Husky CR or KTM motocrosser. It’s different from last year’s YZ but not necessarily better. In fact, some of our testers preferred last year’s YZ rear to the new one. No doubt the aftermarket folks are going to have a field day modifying the ’82 YZs. It needs more progression than it has, maybe the addition of a short primary spring, a common mod to older monos.
This and the loss of 1st gear makes the YZ490 a near hit. It’s a bike you’ll have to spend a few more bucks on before it’s truly competitive against the other ’82 bikes. El
