YAMAHA XS400F
CYCLE WORLD TEST
An Economical Twin With Convenience Features and High Style
There was a time when beginning riders bought 100s or 125s or maybe 250s, and when a 500 was a big bike. Today, most of the new motorcycles sold are 750s and larger and 400cc machines have become introductory motorcycles.
A lot of people think of 400s as commuter bikes, a name tag which may not be strictly applicable. Any of the 400s sold now are quite capable of transporting a rider across the continent as well as across town. But considering the range of powerful and exciting superbikes available, how does one describe the average 400?
A workhorse. Transportation. A commuter bike.
Our test Yamaha XS400F didn't stir the staff road racer to fits of poetic praise, didn't convince the editor to park his CX500, didn't motivate the tourer to give up his XS750 or the off-road ace to fd#ake knobbies.
What it did do was its job without complaint, carrying first one. then another, then another staffer where they had to go. no problem. One man labeled the Yamaha XS400 “a nice little bike." and he was right.
This particular nice little bike started as the XS360. introduced in late 1975. For 1977 the 358cc XS360 gained 3mm of bore size (from 66mm to 69mm), while the stroke remained at 52.4mm. and became the 39lee XS400. In 1978 an XS400-2 economy, spoked-wheel. drum-brake, kick-start-only version was added, known in 1979 as the XS400-2F. The subject of this test, however, is the deluxe. XS400F.
The powerplant is a sohc. two-valvesper-eylinder. wet-sump Twin with a plain bearing crankshaft. The roller-chaindriven camshaft rides directly in the aluminum cylinder head, without insert bearings. and the cam chain tensioner is automatic. Valve lash adjustment is conventional tappet, requiring no special tools or shims. Carburetion is handled by two 34mm CV Mikunis with enrichment circuits for cold starting; ignition by two sets of points operated of!' the left side of the camshaft. Gear primary drive feeds power to a multi-plate wet clutch and a six-speed transmission. Final drive is chain.
It sounds conventional, and is. Even Yamaha calls this motorcycle a commuter bike, and Yamaha engineers listed among their design goals things like simplicity, good mileage and the ability to burn regular fuel. As might be expected, the engine is tractable for its size and isn’t an outstanding performer. At the dragstrip, the XS400 turned the standing-start quartermile in 14.58 seconds with a terminal speed of 86.70. That’s better than the KZ400 Kawasaki’s 15.60 at 81.66, but not as quick and fast as the Suzuki GS425’s 14.43 at 89.91, the Honda Hawk's 14.08 at 90.90 and the Yamaha RD400F’s 14.18 at 91.37.
In this case, there’s a direct, inverse relationship between power produced and gas mileage. The XS400F delivered 58 mpg on the Cycle World mileage test loop, a mixture of city streets, country roads and expressways. The Kawasaki, which is slower than the Yamaha, got 62 mpg, w hile the faster and quicker Suzuki yielded 52 mpg, the Yamaha RD400 49 mpg and the Honda Hawk 48 mpg.
Obviously, for a transportation machine, quarter-mile performance isn’t the main objective, and in all fairness even a slightly slow 400 can outrun almost every four wheeled vehicle on the road. Then, too, the Yamaha’s ability to squeeze 58 mi. out of a precious gallon of fuel in normal use—with no special attempt made to increase mileage—is commendable. With a tank capacity of 3.7 gals., the XS400 has a usable range of 200 mi., with reserve usually needed after 175 mi.
Also important for a commuter bike is comfort. Any vertical Twin will vibrate, and the Yamaha is definitelv the roughestrunning four-stroke 400 Twin on the market. All the others have some form of dynamic balancer to help counteract the normal shaking. Complicating the matter is the fact that the XS400F has the crankshaft throws positioned 180° apart, which means that while the pistons in theory are in better primary balance, the power pulses are uneven. The Suzuki GS425 also has a 180° crankshaft, but overcomes any problem caused by the uneven impulses with a balancer. Both the Kawasaki and Honda four-stroke Twins have crank throws 360° apart, which means power impulses are exactly even, and both have counter-rotating balancer shafts. (For interest, all have plain bearing crankshafts except the Suzuki, which uses a rollerbearing crankshaft. Of the four, only the Suzuki is dohc.)
In practical application, what all this means is that the simpler Yamaha buzzes through the handlebars, seat and footpegs at highway speeds, and blurs the rearview mirrors enough that watching the back door is impossible at any speed. At low rpm, in city traffic the vibration isn’t bad. and the engine does seem to smooth out above 7000 rpm. but at everv speed between 50 and 70 mph the bike shakes> enough to be either noticeable, annoying, or irritating, depending upon the current state of mind of the rider. Compared to the XS650 Yamaha or any British Twin, the XS400 is dead smooth. Compared to other Japanese 400s. it's not.
Around town, the XS400 shines in several ways. First, the engine is less peaky than other 400s, responding nicely at low speeds and doesn’t suddenly come on the cam, yet is willing to pull up to and beyond the red line w ithout any flat spots or lulls in power delivery along the way. Second, the constant vacuum carburetors are more controllable at low' engine speeds than those on other 400s. In many cases, CV carbs contribute to excessive snatchiness and make it difficult or impossible to maintain a constant speed—the slightest movement of the twist grip has the motorcycle accelerating or decelerating. 1 hat isn't the case with the Yamaha, and the carbs improve gas mileage as well.
In addition, the Yamaha’s carbs contribute to excellent cold-start response, an area of serious problems w ith some machines. All it takes in the morning to start the Yamaha is full choke with no throttle, and after a few seconds the bike can be ridden away. Ride down to the street corner and push the choke—which is mounted on the left carburetor body —halfway in, then down to the traffic signal and push it all the way in. There's no waiting until the engine comes up to normal operating temperature. no bucking or stalling w ith the choke on. no trouble with the engine idling at 4000 rpm with the choke on. The carburetors simply work, and that's saying something considering the problems caused bv emission standards carbs on some motorcycles. And because the twist grip must only open two butterfly valves, not raise carburetor slides, holding the throttle open for long periods of time isn't tiring.
On the other hand, the transmission is less than perfect. At the dragstrip. the bike refused to shift into second gear three times when the rider attempted a powershift out of the gate. Even in normal street use shifting is less than smooth, and at times it was difficult to find neutral or first at a stop. The best transmission action came w hen the rider made an effort to shift deliberately and positively (or relied on sheer force during powershifts). The clutch dragged and grabbed w hen hot. especially at the dragstrip. but never did show any signs of slipping at the track or on the street.
There is some debate among staff members as to the necessity of a six-speed transmission. There may be a case that the six ratios are needed only for competitive sales appeal. But it's also true that the engine makes its best power above 6500 rpm (an indicated 70 mph in sixth gear) and that the relatively close six speeds makes it easy to keep the revs above 6500 rpm when the rider wants maximum acceleration. Sometimes, even a commuter bike rider wants to gas it up. and the six speed transmission is a good thing, then.
While Yamaha did a great job building a teardrop tank that actually holds enough fuel, style suppressed function in the case of the seat. Yamaha research shows that people like rounded lines and step seats, and the XS400 has both. But combined with the handlebar bend and the footpeg position, the seat is all wrong for most average-sized riders. One stafl' member, who stands 6-foot-2 and loves touring behind a windshield, thought the seating was
just fine. But the under-six-foot staffers who prefer to lean into the wind thought that the pegs were too far forward and the bars all wrong. The step in the seat fixes seating position and keeps the rider from moving back, forcing a sit-straight-up posture and inducing backaches and stiff necks on the interstate, especially in the face of a headw ind. What's more, the seat is either too hard or shaped wrong where the rider must sit. contributing—with the ever-present vibration —to a numb butt with 20 min. of riding. Several riders also complained that the seat shape caused them to slide forward, bunching pants and pinching privates.
The forks are compliant enough to deal with any tvpe of road surface, from smooth to choppy, but the shocks—even on the lowest spring preload position transmit small, repeating bumps like the expansion joints found in concrete roadways. On the worst section of concrete freeway, the forks absorb every joint while the shocks beat the rider’s kidneys. For more sporting use. the suspension holds up tine, without causing anv serious handling problems. However. as in the case of most Yamaha street bikes, the rider must adapt to instant and drastic fork dive under braking, a characteristic of compliant front ends.
The single disc brakes found front and rear on the XS400 are powerful, although the rear disc is overly sensitive and prone to lock up despite the best efforts of the rider to avoid a locked rear wheel. Especially when downshifting before a turn, the rear w heel locks and skids if the brake is used at all. In braking tests, the XS400 stopped in 33 feet from 30 mph and 138 feet from 60 mph. Braking performance was limited by the original equipment tires. Bridgestone 3.00S-18 Super Speed 21 F2 in front and 3.50S-18 Super Speed 21 R2 in the rear. The tires are mounted on Yamaha cast aluminum wheels.
The tires also limit the cornering ability of the motorcycle, reaching their limits before the chassis reaches its limits. The XS400 responds very quickly to rider input, and is a throwable motorcycle—you can charge up to a curve and throw the bike into it without facing a wrestling match. On the other hand, the Yamaha is very sensitive to sidewinds and road surface imperfections. A strong, gusting sidewind will move the bike across a lane before the rider can correct, but that's a problem with all relatively light motorcycles.
Cornering clearance is adequate. When things begin to scrape, the folding footpegs ground first on both sides, followed closely by the muffler/headpipe junction bolt on the right and the centerstand on the left. Once the solid stuff' has touched down, pushing any harder will unload the tires and start one or both w heels sliding. If the rear end kicks out. that's one thing, but saving a front wheel slide can be difficult. While not a problem the buyer of a commuter bike is likely to encounter, anybody who plans to ride the XS400 hard on tw isty roads had best invest in a set of high performance tires and practice dirt-track slides.
Controls and instruments are first rate. The speedometer and tach numbers glow yellow at night and are easier to read than the numbers found on other brands of motorcycles. The fork lock is incorporated into the ignition lock, a convenient feature not found on all other four-stroke 400 Tw ins. Yamaha's locking gas cap is the best in the business, easy to open and use without any cover flap to get in the way. Because the cap is hinged, it has a place to stay when open, and the filler opening is located just off' center so that it's uppermost when the bike is on the sidestand — the rider doesn’t have to put the bike on the centerstand to fill the tank to the brim.
Yamaha was first with a self-canceling turn signal, and if the rider doesn’t want to leave the signals flashing, there's an easyto-use manual cancel feature—pushing the switch straight in with the thumb stops the flashing.
Maintenance is a snap. The XS400 is simple and demands no special tools or skills for tune-ups. Owners have written in to tell us how much they love their XS400’s looks, and how reliable the bike has been. It's not big enough to intimidate anybody and does what it’s asked to do.
The Yamaha XS400F is a functional, economical, simple 400cc four-stroke Tw in with good looks and convenience features.
YAMAHA XS400F
$1774
