Every seemingly insignificant aspect of their current machinery is refined, strengthened, lightened, drilled and more often than not redesigned to give even the slightest improvement.
Every year the quest goes on. Yamaha believe that competition improves the breed (as do all competitive MXers) and it was for this reason that they bought the services of the legendary Heikki Mikkola. Along with the Finn's riding ability came his knowledge of MX machinery, his ability to gain the most from what he is given.
Mikkola competed in eleven of the twelve world 500cc MX rounds this season. His machinery was almost identical to the machine this article is all about. the YZ400E. Mikkola won nine of the rounds to win the title from De Coster 272 points to 219. Each MX is comprised of two 45, minute moto's making a total of 24 motos during the season. Competing in 22 of these, Mikkola won 12, retired once (broken brake lever caused by another rider) and didn't finish lower than fifth in any other.
In MX that's what's termed domination.
When all is considered, you can't blame Yamaha for rushing a small batch of the YZ400E's to Australia.
One of the first Aussie E models went to up and coming 'A' grader Jeff Thynne. Jeff agreed to show us his new toy so we arranged to have a D model on hand for comparison purposes.
Sitting the bikes side by side yielded few major differences. The most obvious change from last years model is the much improved rear swinging fork unit. Replacing the D model tubular steel unit is a box sectioned swinging arm fabricated from aluminium alloy. The unit is a direct steal from Mikkola's machine. Unsprung weight (where it counts) has been cut slightly and strength has been improved greatly.
Tuning the suspension to suit your own needs and to match the terrain of each and every MX track is simplicity itself. An external adjusting ring at the top end of the de-Carbon shock allows you to adjust the damping characteristics of the shock while a simple ring nut allows you to preload the spring to the desired tension.
The rear suspension set up allows 250mm of rear wheel movement and its exceptionally smooth weight transfer characteristics keep the rear wheel in contact with the ground far more than conventional suspension does.
Yamaha say the bike has a completely new frame, but this is doubtful. Stripping both bikes reveals only minor differences to the frame in the form of lugs, brackets and the chain rollers.
Up front the wheel travel has been increased by 10mm, and is now 25.4cm (10 inches). The tubes from the D model have been retained, while the sliders extend one extra half inch below the leading axle. Internals have been changed with new damper rods to give the forks a different feel.
These forks are again very similar to those of the championship winning bike. They are partially air sprung and partially sprung with the conventional steel coil spring. They are protected from mud, water and grit by rubber boots and in a case of overkill the seals have been redesigned for better long life sealing.
The leading axle design has two major advantages over an in line axle set up.
(1) quicker low speed steering
(2) the facility to extend the fork legs below the axle line.
Another improvement over the earlier D models is the use of more durable and slightly softer foam in the seat. Last year the seat foam had a tendency to collapse causing many a severe case of "achus posteriatus". Many riders repacked their seat with new foam. Trevor Flood confided that he had Maico packing in the seat of his sponsored Yamaha. Trevor hasn't needed to alter the seat on his new E model.
Looking at the tank we decided that it was made of new material as the fuel hadn't yellowed the plastic. On checking with the distributors we found that the plastic is supposedly the same. Apparently the last two digits of the part number signify any changes in material and the part number remains unaltered. We'll have to let you decide on that one.
A new tank graphic is supposedly more hardy than last years.
Looking through the parts book yielded several small changes in the form of new chain adjusters (which look identical). a new back axle, new cables, brake backing plate, exhaust silencer (which also appear identical), chain tensioner, different bars and a new kick starter.
Externally that sums up the new 400. A new rear suspension, altered damping at both ends and a softer seat. Yamaha weight watchers will be pleased to note that their E has shed another kilogram without the help of expensive super metals.
Not surprisingly the power unit has been carefully reworked.
Although the barrel) is new the porting remains the same. Most of the changes appear to be definite anti seizure measures. A new method has been employed in the casting of the barrel) and the new piston has the piston pin offset 1.5mm forward (toward the exhaust port).
Downstairs in the motor the only change is a new crank which has been redesigned with a new balance factor to reduce vibration and increase rider comfort.
The carburettor has had a small copper cage added just below the main jet. This is claimed to reduce fuel froth when the machine is bouncing over rough ground.
Claimed horsepower hasn't altered, however we feel that actual horsepower has been nudged further upward. Maximum torque is not quoted on current Yamaha literature, probably because of a slight decrease.
So how competitive is the E.
For a start they steer better than last years model, particularly through rough sections. The rear end doesn't flex anymore and the suspension keeps the wheels in the best place. On the ground. This is evident particularly when accelerating over bumpy surfaces.
The motor has sacrificed a little low down power for more up top and a willingness to rev out further.
A new chain adjuster, more nylon rollers and probably new material have cut sprocket wear down and the last of the D model bugbears has gone.
The E is a better motorcycle than the D thanks to the likes of Keikki Mikkola. Competitive in its out of the crate state, the YZ400E will give you more in common with the world champ than you ever thought possible.
Back to Top
