Cycle News - Archive Issues - 1970's

but then Montesa started it all 250 moto cr osser y o u ca n bu y. Which means it's abo u t the third lightest 250 motocrosser yo u can buy . OS SA claims 19 7 p o unds dry; Bultaco , 204; Monte sa 2 10; all with reason able ac curacy based on th e ever-fa ith ful bathroom scal e . Wh at those figu res really mean is tha t weigh t di str ib u tio n. how mu ch gas y ou put in the ta n k fo r a rno to , an d th e muddines s of th e course will m ake m ore di ff erence than any dry weigh t differe nce over a 13 pound ran ge. This lac k of heavy is achieve d , in part, th rough use of a partial ch ro me -moly bde n u m ste el frame. The Mo ntesa co uld b e even lighter pro bab ly with total chro me moly ch assis but this is more ex pe ns ive an d more difficult to weld under production co nd itio ns. Also. _ th e frame has n ice , thi ck-wal led tubing and heavy, intelligent gusseting . Yo u migh t be ab le to shave a few pounds in a re-design to no particu lar advantage and risk frame cracking . Th e Y-75 frame, incl uding the swi ngarm , is p leasantly flex-free and un brea kin g. Light ness is furt her strived toward thro ugh the clever use of beau tifully functional white nylon fe nders, a waterproof p lastic airbox accessed by n umberplate removal, and ridgeless Akront alloy rims. There are other reasons fo r these co mp o ne n ts besides lightweight ho n ors awards. The fenders are going to be extremely difficult to damage. (We've stopped saying "unbreakable" ab o ut anything.) The airbox keeps most of the outside environment in solid or liquid form away from the biggest Twin Air foam filter yet see n. Without actually having a volumetric flowmeter, one can suppose that carburetor breathing is not restricted - at all. The new Akronts are heavier gauge, more anti-ding, and stay rounder longer. "How much suspens ion travel is there?" Hooboy, go lly, and wow. Lo ts. Montesa has modi fied the internals of the excellen t Betor forks as they co me fro m the Betor works so that, with stock springs an d about 200cc of the correct visco sity fluid for your weigh t and riding, m ost Y·75s attain an honest 7.85, call it eight, inches of fron t fork tr ave l. It is t he best-feelin g t ravel of any di me nsi ons o n any motocross mach in e ridden so far including o thers with Betors o n them. No oil see p ed from under the distinctive black rubber boots that shroud the tubes of these excellent forks. The ac co rdio n-p leated boots serve to keep grit and grunge fro m attacking the fork seals. That's one reason they don 't lea k and generally go longer between replacement. The increased suspensio n extends, naturally, to the rear axle. The Betor gas-fluid dampers are cantilevered to provide about six and a half inches of rear ax le travel. They are normally Canted gas Beton handle the rear. Specifications FRAME A ND SUSPENSION Single downtube semi-cradle chro me -mo ly and m i ld steel (4 130 and 1040) Wheelbase 56.1 - 57 in. Ground clearance . .. .. .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . .. . .. . . . . . . .10" Saddle height 34" Fron t suspen sion Beto r/ Mon tesa telescopic w/8 in. travel Rear suspen sio n . . . • • . . . . . . . • . .. . • . . •Bet or gas ~j l dampers; can t i lve r moun t provid in g 6.5 in. travel w/140 Ib.lin. springs ENGINE AND TRANSM ISSIO N ; Tw o-stroke 7·port wi th piston po rt Disp lacement • • • .. .• . . . . . . . . . . . . . . . .. . . . . . ... . . . .. . . . . .. .. .. .. ..• . . 2 46 .3cc Bore x stroke . . ... .. . . ... . .. .. .. . .. . .... . .... .... . • ....... .. ..70mm x 64mm Co m pressio n rat io . .. . . . . . . • . . • . . . . . • . • • . • • . • .. . . . •. . . . . . . . . ..• . . .• . . .. 12 :1 Max. horsepower (measured at rear wheel) 2~ .88 @ 7500 RPM on Webco dyno Clutch 7-plate wet Gearbo x 5-speed (l -N·2-34-5) wit h gear-drive primary Gear rat ios (:1) 15t-1 .846, 2nd- l.466, 3rd -l .176, 4th - 0.947. 5th -0.800 Carburetor _ Bing 34mm (Spanish-built ) Air filtratio n T w in Air oiled f oam Ignition . . . . • •.. .... . . • ... . . .. . . . . . .. . . ... . ... . . •. . . • . . . • Motopl at electron ic RUNNING GEAR Wheels/t ires Throttl e Akront alloy ridgeless rims w/Pirelli MX t ires 3.00x21; 4.50 x18 Montesa 80-degree turn (plastic) Fend ers • . . . • . . . . • . . . . .. . . . . . .. . . . . . . • . . . . . . . . . . . . . . . . . . .Whi te f lexib le ny lo n PRICE • • • • . . • . . . • • • • • • . . . .• • . . . • • • • • . • . . • • . . • . . . • . $1595 [approx.] mo un ted with the gas reservoirs at th e top to save a couple of pounds of unsprung we ight. These dampers ar e an enigma. They should work excellently based on the design and their ap p are n t damping behavior when studied o ff the bike. In fact , performance varied sign ificantly from shock to shock. For as yet undetermined reasons, rebound dampin g faded past the point o f co m fo rt or critical co n tr o l after racing 15-30 minutes, a p p ro x i ma t e ly depending on the roughness of the track. The dampers appear to be o versp ru n g with the standard 140 lb . jin. springs. Betor gas shocks work as great as they should until they st o p working. Unfortunately, there is as yet no history for these damping units that migh t what the ne cessary i n d ic a t e m od ificatio ns might be. Betor suggests gas pressures of 88-90 psi. Lower pressures see m to be re quired for m ore progressive rebound. Springs with a 120 Ib.fin . rate will work better fo r many ride rs than the 14 0 lb.fin, coils that arrive wit h t he Betors, All of the riders in vo lved in the Montesa test weighed abo ut 180 pounds fully clad in their natty riding costumes. Perhaps different spring rates will be required for less su bsta n tial racers or those with different riding m an ners. The can tilevered Betors do a first class jo b of keeping the rear wheel on the ground over every kind of ro tten stuff without any of the rear end pitch -up encountered with some LTR suspensions. Th at is, again, until they stop working co rr e ctly . Then the seemingly undamped 140 springs pound Wiggly fins, slim cases and almost 30 HP. your body hard. Qu ality co n t ro l on the shoc ks still ap p ear s t o be spotty . Two 3 0-m inu te m otos under an ad mi tted ly abusive Expert produced hairline cra c ks in t h e t op mountin g eye of o ne o f th e fo ur sh o ck s used. The Montesa fra me su fficien tly and i tsel f appears intelligently boxed and gussetted to wit hsta nd such pounding. It is the in creased tr avel o f the suspensio n t hat is responsible for most of th e change in riding feel and requirements o n the new Montesa, The Y·7 5 sits higher than previous 25 0 Cappras , with 10 inc hes of ground clearance . On e e ffect is that where the YR had directional tracking sta bility second to none, the Y·7 5 has a slight tendency to oversteer. It is a tendency th at will probably be detected only by top experts and pros, however. Attuning slower reflexes to the lightness and responsiveness of the excellen t Montesa fro n t end will be the major adjustment by most riders. One very p os it ive aspe ct of t h is newly emphasized behavio r is that the Y·75 will tu m un der j ust ab out anything . It is quick in the turns and demands quick thinking from the racer . Yo u must pay atten tio n to whe re y o u put the front end. Replacing the front Pire lli 3.00 X 2 I tire with a Barum o r Trelleborg will immediately provide more co n fid ence an d room for error. Like most of the other LT R suspension machi nery, th e Y-75 is not the co nsu m mat e slider of yesteryear . It wants to be driven vertically into a co mer at a very high rate o f sp eed , squared o ff quicker than you mi ght believe possible. and dri ven ver ti cally 1- out of th e co rner. As th e req uiremen t to go fa ste r an d produce lower lap times ove r cabby t err ain has increased , some of t he physica l sensatio ns that make rid ing a bike fun have changed. It m ay not be as m uch fun but it really is faster. Progress has its pri ce . In a straight line from com er to comer yo u never have to back off the throttle. This is whe re seven and eigh t inches of su sp ensio n travel truly justifies itself. " Yeah, but how close is it really to the works bikes?" With the exception of th e o ne-off R&D machin es somet imes prepared for Raym o nd Bo ven, the Y-75 is the bike th at the works-supported Montesa riders co m pete with. Yo u can't ge t closer than tha l. The rid ers may m odify.susp ension , grips , handleb ar s, and suc h items to su it th eir personal prefer ences jus t as y o u and I do , but th at is reall y abo ut it . Even including Boven's bikes, the frame is the same, th e configurati on an d type o f forks are the sam e. the excellent Montesa semi-conica l hubs and brakes are the same . The ubean " tank and new seat wi th in creased padding are th e same. Works Mon tesas ap pear ed this season with gas sh ocks by Betor, Marz o cch i, or Bilstein on the rear; all of wh ich co me on the Y-75 or are purc ha seable by th e American privateer. Where the produ ction Y-75 engine is built for reliability at around 30 rear wheel horsepower, so me of the works bike s are not. The basic motor can be twe aked for a four-six horsepower in cre ase to m at ch the works bikes but th e factory knows th at it must then be inspected and rebuilt after every race. They also know that most privateers ar en 't likely to do this. But don 't feel cheated. Twenty-nine to 3 0 horses on the ground is more than you normally use o r, in most cases, can ever usc . A bike with th e potential to go as fast as the Montesa must also stop quickly and positively or the advantage of speed is lost. You'll make more passes on m ost motocross co urses by o utbraking yo ur opponen t than by o utspeeding h im. The brakes in Mo ntesa's un ique and effective hubs are all you need and m ore. The fr ont bi nder is predictable, progressive and co uld be a new favori te in mo t o cr o ss fron t brakes. The only co mplaint, which was resolved by simple pe dal adjustment in the case of one rider. was that t he rear brake was too strong. Even with its cable operation, it locked up a few times un til the fresh ly cleaned b rake shoes bedded in. Then both brakes felt in credibly strong and fade-free. One hot set-up is to chamfer the leading outside edges of the rear brake shoes to make that brake feel more progressive . Both stoppers also work when wet. They set a standard for other l\IX bike builders to shoot for. (Contin ued on page 50) The right side is clean and has a lo t of alloy pieces. ..,. 49

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