Yamaha’s YZ400FR – bred from world cham­pi­onship MX suc­cess

In February 1978, af­ter Mo­tor­cy­cle had ac­quired the ser­vices of Vic East­wood for an ex­clu­sive test of Heikki Mikkola’s 1977 500cc world cham­pi­onship-win­ning Yamaha on which the YZ400FR was based, be­tween them, Vic and Chris My­ers wrote the fol­low­ing.

Classic Dirtbike - - Archive -

Vic East­wood’s snap ver­dict af­ter an af­ter­noon’s ride on last year’s 500cc world cham­pi­onship-win­ning Yamaha was: “So smooth -- the power, the ride, the con­trols… ev­ery­thing is so smooth.”

The big Yam had started up will­ingly af­ter a few drops of wa­ter had been cleared from the carb. Vic had a chat with Mikkola to check out the bike and then gin­gerly set off around the twisty, hilly course set in the mid­dle of an ap­ple or­chard.

“The go­ing was muddy and very slip­pery, but Vic soon gained con­fi­dence and speed -- he was ob­vi­ously en­joy­ing him­self. Mikkola went out on his new bike a few min­utes later and for a while the two cir­cu­lated to­gether, play rac­ing.”

When Vic was even­tu­ally prised off the bike, which was so light he’d lifted the back wheel up off the ground with no trou­ble be­fore even get­ting on to it, he said: “When I was rid­ing the bike, I just wasn’t con­scious of its weight at all. It must be right on the FIM weight limit, but what re­ally struck me was just how easy it was to ride, with no vices at all. Joe Bloggs could jump on this and go well.

“The smooth­ness ap­plies to the whole bike. Even the seat is good­ness knows how thick – it’s so com­fort­able. The sus­pen­sion makes it a tire­less bike to ride, too, with 11 inches avail­able at the front and the rear.”

The rear sus­pen­sion was so good that Vic hardly no­ticed the bumps, but he found the front spring­ing a bit hard (Mikkola’s me­chanic did say that they’d put a harder set of springs in at the end of the last sea­son).

“With ad­justable damp­ing in both di­rec­tions and vari­able preload on the monoshock unit, the bike could be tuned to suit al­most any­one and any cir­cuit,” wrote Vic. “The Yamaha works men have ob­vi­ously found the right set-up for Mikkola and it suited me too, but I stand by what I said when I rode the pro­duc­tion bike -- I think it’s far safer for the aver­age bloke to leave the set­tings alone.

“I found the rear sus­pen­sion bet­ter than that on the pro­duc­tion bike I rode last year. The works bike has more move­ment at the rear and it works very well. I can’t say that the mas­sive al­loy box sec­tion monoshock rear unit was any stiffer than the pro­duc­tion tubu­lar de­sign, but this is clearly lighter.

“The front sus­pen­sion I found about the same, but again I think the works ver­sion has more move­ment avail­able.”

Like the pro­duc­tion forks, the works forks could be pumped up with air to give a vari­able pre-load.

Once he’d be­come used to the bike, Vic East­wood found the steer­ing very pre­cise, too. “It’d go wher­ever I wanted, no prob­lems,” he said. “If I was go­ing a lit­tle too fast in a bumpy rut it would just bounce out. I could just drift along feet-up a lot of the time and pick my way over the holes -the smooth en­gine power helped here.”

He found the en­gine’s power de­liv­ery much dif­fer­ent from that of the 1977 pro­duc­tion bike. “It’s so much smoother,” said Vic. “The power comes in smoothly right through the rev range. Just cog up and away you go, but on the other hand the pro­duc­tion ver­sion is fiercer -- it comes on song and takes off.

“The smooth power makes the works bike so easy to ride, and it doesn’t do any­thing funny. Com­ing out of a cor­ner in the right gear, you just open it up and blast away. The ac­cel­er­a­tion is great, and Mikkola al­ways got great starts last year.

“The gear­box is smooth and pre­cise, and once I got used to the bike I found that I could go around the whole course, hills and all, in third.”

While East­wood found the rear brake su­perb, the front wasn’t as pow­er­ful and pro­gres­sive as he would have liked. Although he stalled the motor a cou­ple of times when lock­ing up the rear wheel, all he had to do was take off the brake and it would pick up again.

“I’d say the com­pres­sion ra­tio must be very low,” he added.

Vic found the Yamaha easy to start, and found the clutch su­per smooth as well. “It’s very light, tire­less to use, and suited the motor per­fectly,” he said. “All the con­trols came to hand eas­ily. Mikkola and I are of sim­i­lar build, although he might just be a lit­tle bit heav­ier, and noth­ing had to be al­tered to suit me. I just got on and away I went. “Ev­ery­thing about this bike was just right, and one lit­tle de­tail I liked par­tic­u­larly was the in­te­gral cover over the edge of the twist grip to keep out mud and dirt -- only a small thing, I know, but it shows just how much thought had gone into the prepa­ra­tion of the bike.” As a for­mer de­vel­op­ment en­gi­neer and works rider, Vic was very im­pressed by Yamaha’s su­per smoothie. “There’s a lot to be said for a bike you can ride flat-out and un­der con­trol,” he said. “Un­for­tu­nately you just can’t do that with a lot of mo­tocrossers be­cause they are just too fast. Yamaha has got it ab­so­lutely right. It’s a fan­tas­tic bike and it’s pi­loted by a fan­tas­tic rider. Put the two to­gether and you’ve got the world cham­pi­onship -- right?” 

Vic East­wood, cov­ered in mud but ob­vi­ously en­joy­ing him­self, is cap­tured in full flight on the 1977 500cc world cham­pi­onship-win­ning Yamaha mo­tocrosser.

In be­tween Vic’s rides, his gloves were warmed on the cylin­der head of the 400cc mo­tocross ma­chine.

On the 1978mo­tocross world cham­pi­onship pro­to­type, Heikki has the ad­van­tage over Vic as they plough into the mud splash.

Vic East­wood (left) dis­cusses the works Yamaha with 1977 cham­pion Heikki Mikkola.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.