Yamaha Yz250e
YAMAHA YZ250E
CYCLE WORLD TEST
Yamaha first introduced the YZ monoshock in 1973. It attracted attention. It was a radically different approach to long travel rear suspension. Many people claimed it was the ultimate suspension.
An equal number of people didn't like the principle and voiced objections like: It makes the center of gravity too high, the rear wheel kicks, it’s not adjustable enough, you have no choice of shock brands, etc.
Even so. monoshock Yamahas have become popular with many riders. Many companies offer different monoshock damping changes, springs and long-travel kits. Almost every year Yamaha adds more travel and offers more adjustability. Their newest, the 1978 YZ250E has damping that can be adjusted externally to 17 different settings. The spring preload may also be adjusted and different rate springs are available. Internal pressure is adjustable. another tuning feature. The shock itself has changed from a bladder-type, gas-charged and rebuildable unit to a lighter DeCarbon-type nitrogen charged non-rebuildable unit.
The newest YZ also has a chrome-mol\ steel frame. Strangely enough, the YZ is the last Japanese MXer to use the lighter, stronger frame material. This makes the new bike feel more solid and helps reduce the overall weight some 9 lb. Although the frame is finally made from chrome-moly. it still has the cluttered, cobbled up look representative of monoshock frames. A large main backbone houses the shock unit and has screwdriver holes to allow external shock damping adjustment. Double front downtubes are used in front and layer upon layer of stamped gusseting strengthens the steering head-backbone-dow ntube joint. These layers of metal gusseting run down the front downtubes and their termination is staggered on the tubes. One of these plates continues to a point below the front motor mount bolts. All of this adds a lot of strength and rigidity but makes for a messy looking frame.
A Chrome Frame and New 6-Speed Transmission
To go along with the new frame material, the swing arm is now aluminum. It is made from rectangular aluminum stock and has nice welds on it. This new swing arm effectively stops most complaints about swing arm ilex.
Up front the good looking, leading-axle, air/oil forks from 1977 have had the engagement lengthened to reduce flex and bind. This change has made them work almost flawlessly. Yellow fork gaiters help keep dirt from the seals and stop rock damage to the stanchion tubes.
The new engine contains a close ratio 6speed transmission with perfect ratios. First gear is tall enough to use for starts on many tracks. If the start area is slippery, a second-gear start may be needed but some bogging may be noticed unless the rear wheel breaks loose. The reed cage utilizes six large pedal steel reeds. The reed cage feeds fuel through two holes in the rear of the piston's skirt. Fuel also enters below the skirt when the piston is at the upper limits of its travel. The piston uses a single straight-blade-type ring. A single ring is claimed to give more power with less drag, but replacement becomes more critical. Ring end gap should be checked often.
The smaller center cases look as if they came from a 125. They are shorter, narrower and help drop the overall weight of the bike some 9 lb. from last year. Horsepower has been boosted some. This increase can be felt at higher revs, but power at lower rpm has been sacrificed. It will pull at lower engine speeds but the dramatic power happens at the higher revs. Naturally a CD1 ignition is used.
The clutch in our test bike didn't engage like a toggle switch, but also didn't have a progressive feel. Almost every rider complained about it feeling mushy.
The drive sprocket placement is still quite a distance from the sw ing arm pivot. Two frame-mounted plastic rollers (one below, one above the chain) help control chain tension. The swing arm also has a plastic roller to keep the chain from sawing into the aluminum. Further chain tension is controlled bv a spring-loaded tensioner mounted just ahead of the rear sprocket. This device is protected by its ow n tubular aluminum guard. Nice!
The F has some of the biggest tenders on any MX bike. They are wide, long and flexible. They protect the rider from mud. ete. very well.
The Yamaha has one of the thickest seats around. It measures over 7 in. thiek.
A modern snake pipe loops over the radial head and winds its way down the left side of the frame, behind the number plate and then enters a large non-repackable silencer. It is mounted in good brackets that isolate vibration from the frame.
The footpegs and brake pedal have sawtooth tops and don't get slippery w hen muddy. Even the kickstart lever is heavily ribbed to prevent the boot sole from slipping off w hen wet or muddy.
YAMAHA
SPECIFICATIONS
$1568
POWER TRANSMISSION
FRONT FORKS
Kayaba leading-axle fork
The YZE is equipped with the long KYB legs, offering much travel and engagement. Damping and spring rates are excellent, as is the very low static seal friction component. The result is a high level of control with no sacrifice in comfort.
YZ250E
DIMENSIONS
REAR SHOCKS
Kayaba DeCarbon monoshock
The DeCarbon monoshock on the Eseries YZ has been changed only slightly, but with good results. The rearwheel kickback of older units is gone, and control has been improved. Adjustable damping (in 32 increments) and preload of the single-rate spring allow a high degree of fine tuning.
The E’s handlebars are shaped to lit a w ide selection of people and are rear set on the top triple clamp. This position allows the rider a choice of fork height to suit different conditions and makes fork maintenance easier.
The YZ has some of the nicest levers we have ever used. They are a dogleg design that can be easily reached and work flawlessly. Big cables are attached to them and well routed through nylon-lined loops.
The new YZE is an attractive package when new. Its yellow and black color scheme is enhanced by bright yellow' fork boots. Aluminum fork legs, sw ing arm and rims add to the flash.
The YZ’s looks deteriorated rapidly on the first day of testing though. Mud soon scratched the plastic tank and side panels. Before the end of the day both decals fell off of the tank's sides. Once the decals departed, the tank’s shape looked completely different.
Most of the rear-end kick associated with the mono is gone. Both ends of the machine worked smoothly and reacted easily to small and large bumps. The only handling flaw we could find was a tendency to skitter around when braking into a whooped corner. The normal mono top heaviness is still present and the bike feels much heavier than it actually is. Weight guesses from the test riders were mostly around 240 lb. with a half tank of fuel. Everyone was surprised when the scale showed only 228 lb.
The general handling is somewhat slower than most MX bikes. It is more forgiving than most and a Junior rider w ill have a little room for error without instantly being spit oft'.
The better frame metal and stronger aluminum swing arm has given the new YZ a more solid feel. It no longer feels like it is twisting in the middle.
Trying to find a 250YZ at a dealer in 1977 was almost impossible. The demand far exceeded the supply.
With all of the YZE’s improvements, it could prove even harder to find in 1978.0
