Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125986
Yamaha MX400 .- s-. 0.. -c By Richard Creed It's hard to figure Yam ah a out. Barely eight months ago they astounded the motorcycle world by rele as ing their ultra trick YZ M onoshock models on an un suspectin g public. The results were devastating. Rave reviews flooded the mo to-monthlies and cy cle press, riders stormed dealers showrooms with hard earned dollars in their hands eager to buy the ultimate mo tocross mach in e. "By, Gawd, Clem, it's jes' like Pie-ears bike, look at that p aint job! " The resemblance to the National Champion 's bike was more than paint deep as many zealous buyers soon found out. The YZ production bike was about as scarce as the works we ap on and its near two grand price ca used many would be Joels to rethin k their racing co mmitmen t. Th ere w as one other ar ea for c o m pa r is o n. Th e YZ d emand ed atten tion just like its factory team co un te rpa r t. No longer co uld th e wee kend warrior h ose off his ego tool at th e loc al soap sq uirter on th e way to the rac es Sunday morning and ho pe to survive through the day. The YZ suck ed sand through its air box co nnecto r hose , vibrated nuts and bolts loose and gulped water into its one lung lik e a thirsty beggar. Besides being he avy with th e greenbacks. and a whiz with the wrench , the YZ also demanded of its owner a riding st yle that not everyone co uld ada p t to. Most YZ riders are probably still riding their bikes the wrong way . But , for those who were willing to adjust to the YZ the rewards were immediate and plentiful. It won and it buil t a solid following among riders competing in both Amateur and Expert classes . Now, Yamaha has taken the lessons learned from the YZ racers and applied them to their standard MX line and produced, for all intents and purposes, a motorcycle superior to its more expensive predecessor. At a list price of $ I ,499 the MX 400 is priced righ t in the middle of the Open class market. Yamaha MX series bikes hav e always been known for their robust reliability, ab un da n t power and less than subtle handling. They were b ikes derived from the enduro series and were never at home in rigorous hi gh spe ed competition. The new MX 400 is. Provided the monoshock unit is tuned to the owner's weight and riding style and th e track surface. The key to the whole motorcycle is getting the rear su spensio n dialed in correctly . To do this y ou must go to a Yamaha dealer. The first tim e out on the bike, on a sandy whoopdee filled course. found test riders in im m ediate con tac t with th e ground. On e rider wound up with his leg trapped between the rear wheel and the monoshock swingarm. After that we too k the bike to Bill Kasson Yamaha for a shock cur e and some other personalizing. Kasson ch an ged the nitrogen gas pressure, cut one inch off each end of th e handlebars, ch an ged the fo rk oil, dropped th e forks down to YZ measurements and put on some Hallman GP grips. Just chan ging the pressure of the nitrogen gas improved the handling a t the rea r considerably. But changing the gas pressure is just one of three c ha n ge s that can be mad e either separately or in combination. If the full range of possibilities is us ed you ca n diddle with t he rnonosh oc k unit fo r weeks working o ut over 300 di fferent co mbin atio ns of spring te nsion . oil viscosity. an d gas pressure. Oh, o ne ot her thing, as th e rnon osh oc k works t he gas e x pa n d s and fo r "ideal" h an dling it should be siphoned off at t he end o f each rno to . The factory rigs have a built in rel ease valve fo r this purpose. But we 're getting ahead of ourselves. Let 's go b ack to th e fro n t o f the bi ke and work our way b ac k. The front end is standard YZ whi ch means it is functional and ultra clean in app earance. No other bike can boast of a slimmer set of front forks . Coupled with the lightweight aluminum hub and magnesium brake back plate the MX 400 gives off an immediate feeling of lightness. But. at a claimed weight of 228 pounds it is 10 to 15 pounds heavier than so me of its competition and t he additional weight is in the monoshock suspension which is carried high up under the tank. A new rider, unfamiliar with the YZ's co rn ering manners may take a whil e to adjust to the bike. Instead of trying to force th e bike into cornering differently it would be best for the rider to adjust his style to the bike. Keeping the bike vertical, sq uarin g off the turn tightly an d blazing a w a y with th e MX 400'. instant horsepower seemed to work best. Sin ce the frame is of YZ geo me t ry , has the s am e f orks and monoshock rear su spens io n. a YZ rider would have little tro u ble ada p ting to the big str o ker, What ? A YZ rider switch to an MX model? No way! Don 't be so sure. The MX 400 has enough unique features to stand on its own merits and man y a prospective YZ buyer would be wise to co nside r the MX 400. Why ? Cheaper price, by about $3 00 for openers. More importantly, the MX is mor e pow erful. h as man y o f the annoying bugs of the YZ wo rk ed out, has many detail re fin em ents, and we feel, will prove more reliabl e in th e long run. We base this feeli ng of co nfi dence in the b ike's lo ngevity on th e new air box design and th e new eng ine. The air box is still a dual element model, but houses filters that are lar ger th an the YZ and th e air box is of a mu ch better des ign and better made . Th e YZ engine is almost powerless in p rotecting itself from wat er and mud. Not so th e MX mod el. A large b lac k plastic cen t ral sec ti on cappe d at b oth en ds by covers keeps even th e most determined grit gri nde rs fr om en te ri ng the carbo Throughout ou r time wi th th e b ike th e filteri ng ar ra nge me nt never failed desp ite on e race under ne ar monsoon co nditions t ha t changed to 'slee t and finally snow. Repeat ed washings wi th high pressure hoses also failed to h inder the MX 400 's first kick starting ab ilit ies. T his untemperamen tal behavior has always be en the main app eal of th e Yamaha MX lin e an d it has not b een lost in th e exo tic a. Cold weather did not det er it e i t he r. Sub free zing tem perat u res required only two or three boots of the folding kickstarter with the ch o ke on to bring the radial he aded engine to life. The carb performed flawl essly providing co nsid erable low end without co m pro mi sing top end pe rfo rmance. In fact the MX 400 had plenty of guts to pop, not pull. the fron t wh eel in the air in fourth and fifth gear. The only thing ยท we wish that Yamaha would do is to ch ang e the cho ke arrangement. The pull up and turn rod is small and hard to operate with gloves on. With wet or muddy glov es it is a near impossiblity. The new e ngi ne should not be