Honda vt750c shadow road test (1983)

Page 1

HONDA IIT75DC SHADDIll/

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Here 's the Honda version of The Look Tha t Made Milwaukee Famous. If you think the styling of the VT750C Shadow is radical, Brother, you don't know the half of it.

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0 Okay, lry this one lor size: The VT750 Shadow is the most radteal mo路 torcycle Honda has ever built. Maybe it 's not radteal in a technological way, though there's plenty of innovation and

k>ok , in the same way that there is a Mercedes路Benz look, and it would be

preuy startling to see a new Honda

more than a couple of engineering

automobile that tOOk al its styling cues from Stuttgart, nicht wahr?Frankly, we don 't caro how a mo torcycle lOoks We do care about how motorcy<:les

genes. The Shadow is the most radical Honda in the way it looks and in the way it interfaces with the rider.

work wtth their rkters, and here aga~n the Shadow is the most radical Honda we've ever tried- because tho VT750

As for looks- all the styling cues seem to have come from Milwaukee, and Willie G. Oa>Adson must have been flabbergasted when he saw the

is much less a rider's motOfcycle than any Honda we've tried. The riding posiI)On is awkward and uncomfortable. The way-out-front footpegs and contrOls draw the rider' s legs forward; the

bnghHhink to i mpress anyone who has

Shadow. There is, after all , a Mawaukee

31


rider's body posilionmg is certainty more passive than that required by the Ma.gna. I<X example:, and absolutely un~ke the naturaty active stance com· mon to standard and sport bikes. whiCh posrtion riders aggressively. It's hard to befieve a company that builds Sabres and Ma:gnas and Inter· ceptors COUld produce a Shadow-un· til you think about it Honda can tat<e this exttemist position because the company has its perf<Xrnat'ICe and tour· ing and racing segments so well COV· ered. As lor the street-bike future, Honda ob"'loosty believes there's 00· rnand out lhefe tor great variery in ma· chinery. The corporate honchos in Tokyo aren't belling on one particul<tr

~ <X style 01 type; Honda WQUid no more gamble rts str&eH>ill.e future on Shadows than it woold on lnt8fceptors. In short, Honda can aff<Xd to bel many Chips in many places. Consider the Shadow a way·far·out Ouiser. a chip placed at the Vert edge of the mart<etplace CheCkerboard, far from tho center squares occu~ed by the Magna and Sabre. Farther out, we think, than other cn~ser·style moiOfcy· des, including Yamaha's Virago. Now for the multi·mitlion·dOilar questions: Wrll the guy who already owns a Clurser·type motorcycle- be it A.mcri can or Japanese, twin· or four-eylit'tder-trade it away to buy another, more radical cruiser? Or tor that matter, how many guys who own any other kind Of s\)'1e of motorcyde would be in·

terested in buying a. way-rad ShadoW? Only Honda can alford to spend the miMions to fiod out- by buik1ing the Shadow- Honda has played the edges ol the board before. Honda put a ci'Mp down called the CBX, which was at· most as far from center as the Shadow, but in the opposrte dlrectron. ThOugh the SD.-cytinder Superbtke was war!Tiy received by the press, the CSX- Iong· term-flopped. But Honda rs back to gamble once again, thfs trme w it h a more timePfO'IIen engme cooliguration. What can be innovatfve about another V-twrn? Plerrty. This 750 twrn rS bu~t around what is arguably the most techoologr· caty sophrst1cated Vee ever designed. Hooda's choice of a 4S·OOgree Vee cooflgurahon rs ntiaty surPffSing: 90C'<O.t


Under the Milwaukee-esque bodywork lies Japanese technology-a liquid-cooled, 45degree Vee coupled to shaft drive. Only Honda could do it.

degree Vees have been tradittonaNy chosen for smoothness because they provide perfect pt'imary balance. All o ther Vee configurations inherently produce more pt'imary vibra tion. often enough to turn a bike into a real shaker. Engine counterbalancing sys tems. sometimes emph)ycd to counteract pri-

mary imbalances, add weight, bulk, complexity and cost.

Unfortunately, a twin with cyltnders onset 90 degrees takes up a k>t of space, IOI'cing other design compromises. In the past, engine designers have followed one of three paths. Buikt

a Vee less than 90 degrees and live with the vibl'ation. Or add counterbal· ancers and cope with the complexity, etc. Or build a 90-degrce Vee and extOl the virtues (and ignore the drawbacks)

of a long wheelbase. typtcalty unavoidable with that configuration. Honda. with its technological cxp cr· lise. searched for a different route. The factory amended the book on V·tWin design by introductng to the motorcy· cling world a slick bit of established engineering: staggered crankp1n s. Typ· ical V·twin motorcycles have a c om· mon crank pin for the two connecting rods; not the VT750. The Shadow uses two offset crankpins separated by an unsupportod flywheel (like the Okt Brit· ish vertical twins). Honda's engineers offset the crankptns to "fool" the en· g1ne 1nto acting as if it h as perfect pri·

mary balance even though the actual cytinder angle is narrower than 90 de·

grees. Honda' s engmeers developed the formula

X- tao•- 29.

where

X is 33


the amount of cnnkpi"l otf$Ct neces-

sary with a cyinder angle ot 9

degrees. So for a 45-d&gr&e Yefl, X - tao•-(2 X

45•). In this case, X works out to 90 degrees ol ~pin offset . With thiS

lorrTIIJa, Honda's engineers can de\lelop a V·twin o f any practical conl9uration w.th perfect primary balance. The new VT500 V·twin, as an example, has a vee angle ol 52 degrees and a crankptn oftset o t 76 degrees. While this bit ot eogmeemg sleight ot hand eftectively e6n"'inates primary

imbalances, !• &Q<18vates another type

of engine vrbratiOrl: rodung couple. Stretchng the o ffset between cyindef bore centcrtinn increues rocking couple, and thanks to the duai·Cfri·

..

pin and center-llywtleel arrangomont, the comecting rods in the VT's plain· bearing cr ank are centered about 38mm apart. The b6g Ducati l30-degree V·twin. in comparison. has a C)tndef offset ol oNy 22mm because it uses a common crankpln. So in this aspect Honda sill struck a compromise. The Shadow has bore and strOke of 79.5 by 75.5mm and 153mm connect· ing rods. A rod leogth two times the stroke distance iS la.irfy lOng l or a mo-torcycle, but not unusual; more lmpor· tanl, it helps reduce secondary engine imbalances. A "'-'-domed piston turther reduce$ engine '-Abration by trimming reaprocahng wetght-important when yoo're dealing with two big Slugs. The three-valve VT head uses a compect, heart-shaped ¢01'1"1bU$1i0n Cham-

ber teaturing two spar'll plugs, one on each stOO of the head. A singte ignition coil fires the two plugs Simultaneously, enhancing rapid and c omplete fuel buming; Honda claims the dual·p4ug design rrrp-oves luel economy by up to 30 percent ' ' low engne $pll$ds. The two-plug setup may also reduce exhaust emissions: the VT ignition curve runs with a maximum advance o f Ody 26 degrees before top dead center (35 degrees BTDC is the norm theSe days). CVQ.(


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A QUICket' tgf'lllion bum also lorestals desp~te a relatively high

detonation,

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porta. Tht Shadow's vaiV'e atemt are lOng and llim. and the vaNe heada

9.8·1 comptHtion rabo, the VT ran on hi~ a tulp Shape for mproved Aow a1 grades ot puonp Qat WithOut pinging. Alto, the porta are de.an and ahlped The two illlake vaMtl each rneUI.II'e lor opt1mum Uow; each port 111e1 31nm In dwnetlf, whle 1he exhaust str•t out of the valve . . ., .,.., to valve • 40rrm KrOSS, the ll"'duded valve .ngle II 1 retnllkabty nanow :rT

T'ee-Y81Ve hMds ott• two-valve OYef

11'-

ptOmOte good breattwo, then bendl

Tht VT750 bnngs a ~ong-overca.. advanlagos t•h.r"e to motorcycling. mu'\ten.noe-

designs because they

fr.., hydral.fic vatve ad)Oatment AI

Each of the VT'a rockar arms mounts on an ecceotnc shaft that fi"'I\\es back

and forth as the rodter arm pfvot1. AI the ecc«llric rocktf·arm lhlf1 IUIM it raises or loweft the rocktt to tNWitain a zero-dearance retlbOnthp between the vatve, rock• and CMI:IIhaft Con atlnt pressu'e on e&thet the bottom oC the rocker-arm Wll (from • trycha.* ift•l or the top of ttMI Wit (from an ISM-I spring and Shalt) helpe keep It

can low benet on the Intake stroke. thOugh the Shadow uses a lingle I'TIOVII"IQ 1'1 the ptOC* dirtctiOO. especialty at lOw levefs of valve hft Stl. the valve treln Ia 11mpler and less

0"--ilfhelld camshaft and rocket armt, It

crowded than a lour·valve configuration, and fOfelng spent gases out on the exhaust attoke is seldom a problem. The ~ exhaust valve design allo eliminltet the diffio.lt-t<HXW'Itrd hot spot betwHn the two exhaust

l1ke thOle common to e.utomobl&4" ln-

dottn't use a hydraulic tappet system atelld of using camshaft·actuated tappets Wl the valve train, the VT has a vtriatiOn of the eccentric shift Mtup liNd to atter vaMt clearances n ttMI okt

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1n addition to being mtintenance· free, the hydrauNc vllve-tash adjutters offer another bonus. The running toltfances necessary With 1 manualy set valve tra.10 typecdy requn camlhlft k>bes With king. gently IIOped to open the vahoel ltOwty; this can CM.~M sm.~ variabOnl i'l tm-

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k>Oks emost ~ke an overgrown oil lrT7511C SIIADDW 11coolef An Metric tan, mounttcl be-

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r.o tl'\at hurt 10w «Ki power and muo

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~Kit

=

poorly With the vaMt

ltM"' I'\II'WW'IQ ~Iandy at z.a dnr· MOe, VIIYt tltY-.g holds c:omtanl and

the cam prolilll can be mote r.oal, the vaiYes open • lillll

Eectl held has Its own sltnt-type

Chain to dl'rVe the cams; the front cylin· deri8dl'lvefloflthetefllidtofthl c rr i, thl roar cyindef oft the right E1Ch camcht111 has its own automatiC ttntior'loer, ending adjusltrlef'll wornot The C)'tindera' bold !inning is primer fy cottntbC-the VT750 reliel on lkJJid coot.ng The long, narrow rad.ator moun11 on lhl front of the lr~m~ where

twld the raclatOf, tupp6ements altlow lJke •tt iQulcf-<::ooted r•t~vtt. the Gl.1100 Go6d W.-.g and the V45 s.br.. Mlgnl. the Shadow hu cytinders With cet1«11._.,10~hiNIIrMtltt

Unliketheothertwobilkn.thevracylinderl are not pw1 of the erankc:Uet; the Stwdow uses vertiCally spirt cases and MJ)arate betfet.. TO r~ produetb-1 eo&ta. the cyt.nc~«a and ho.ot •&eh a..e ~from comroon cast.nga~ verlatiOf'ls in mach.ning dllltrtf'ltjatt rear from front to proven! acctdtntal IWiiehwlg Large straight-cut geata pe.M power tromtheaanktothetr~ The big 66-tooth dnYen pmwy QNII' • ac-

tualy two thrner geata "ap6it" and off· set w1th spring tentlon Th1s trrangement reduces backlash bl· tween the pnrnary geltt. CUI!Jng gear wh1ne Power passes through the dutch to • tbl-spMd geetbolt. the bot·

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jump to the OW«tHe lixth The VT750't c:Mch illl"'f''IYative 11'11 rurber of ways Fnt, the dVICh actu· ties vta tlydfatMct rtthef than cab'e In additiOn to PfoY!dlng light dutCh pVI, the hydraiAic setup automttiCIIy cOlT\' pensates lor wear, fMimlnltii'IQ thl r.eed tor adJUStment A diapt~~lgm dutch spMg replaces thl mote common ooil springs. narrowing the eotwt un~t Al-

tnougll<>aplvegm---· taon

oYet <::011 spMgt (1eYet effort <""-£


-111'75DC SIIADDIIII remains more cons•stent throughout

the lever travel), the switch was lafgety dictated by the add•tiOn of a Sprague ~one way) clutch, InCreasing the diameter of the assembty. The idea of addng a Spraguo clutch actualy came from the NASOO r&(ing

program. The one-way clutch

1S

de·

sfgned to eMw'late rear-wheel lockup

caused by high engine compression during rapid deceleration and quick downshiftiOQ. Tho Sprague d utch con· trois half tho dutch plates, which wotk w1th the other dutch P'ates to deliver

saddle it's time to find a rest stop. The Cruiser mode may wort< on the show· room floor and lor quick trips around town, but the riding positiOn defeats even medium-range touring and effec· lively discourages fast rid •ng o f any k1nd. Two-up hauling IS alSO dif'ficlAt, our passengers condemned the thin, short and narrow seat and complaW\00 about the shOrt Sissy bar, whiCh o ffers l ttle back support. The VT' s chassis and runn.ng g ea r limit the bike's vefsat ~ity jus t as much as the seating poSJtion. The suspension is soft, conformng to the 750's boulevard c.u•ser applicatiOn. Fof1( ac· tion is good on the freew ay, but the rear end sacks so much under the rid· er's weight that the ride 1~ harsh: hoaVIOf testers ccxAd readily bottom the rear end over large bump$ and hOles. Overall, the freeway ride is ac· ceptable-but not state of the art.

One fast trip down a rwisty road ro· veals a number o f handing shortcomi ngs. The fork is underdamped lor h ig h·speed, ba ck road cru1sing. The shocks perfOI'm poorty. In l ast sw eep· ers, bumpy or smooth, the rear eod I"IObby·hotscs. II this happens in a left· handll'r, things get 8XCIIW"Ig qvickly; the sidestand grounds heavly and keep s b oun c ing o ff the p a \lement as the hobby tlorSing continues. Considering its steel'ing geometry, 32.0 degrees of rake. 5.510Ches o f trail and a 60-irlC-h wheelbase, the Shadow steers hghtly. We expected trvck·~ k e handling, but the VT responds wei to rider 1nput. Tho front end , however, doesn't inspwe cornering coofideoce: il giVes little feedbaCk through the handlebar, so you're unsure if the front is shcklnQ or losing traction. The brakes are one of the Shadow's strong points, ~onPfl(}fi "8J

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power in the normal !ashton during acceleration, crui sing and notmal de·

celetahoo. But with heavy backloadiog , when engilc braking wovld normally be sufficient to lOck up the rear wheel, the Sprague ck.Jtch slips. This diverts the backload•ng IOfce through just half

the ClutCh, whiCh keeps me rea~ wtteet from lOcking yet s til provides plenty of eogine·compressfon braking . Although the clever dutch system makes much sense lOt race bikes and sport bikes . it seems out of ptacc on the Shadow, ob· viously designed few cruising. If you realy w an1 to ride, the Shad· o w' s seating poSJiion is a wkward and wrilating. The footpcgs and controls are much too far forward to l)(ovide rider support and the sloped po!'tion o f the dished seat forces you into the "taid·back" riding posture whether yoo like it or nol. The pul ·back handlebar o ffers no help: it too fOrces y0u to sit back. Togethet, these pieces demand that you nde in one uncomfotlabfe po· s•tion : you can't lean forward, you can' t move back on the seat. and there ts pract•caJiy no way to use the passen· ger pegs l or relief. You' re s1mply trapped. A fter an hOur or mote in the

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Hond• VT750C ConMue<1 38 the front dual discs provide plenty of stopping power with good feel, and the rear drum wOt"kS weN. The Shadow's engine is strong for a V·twm, though untemart<able for a 750. Wrth a showrng of t2.87 seconds at 101.92 ITIIIcS per hour, the VT is quicker than Yamaha's Viragos, but it trails the current lour-cylinder 750s. But big twins, of course, are known and appro· ciated lor therr tow-end torque and overall power characteristics. In these respects, the Shadow does well. It has a wide power spread and revs willingly. Despite Honda's tnnovative use of offse t crankplns, vibratron appears at certain eng1ne speeds. At cru1sing speeds vrbratron is well controlled. Thanks to the overdrive sixth gear, when tho VT turns a modest 3488 rpm at 60 mph, only an unobjectionable throb cornes through the handlebar. After 4000 rpm the Shadow is down· right buzzy. The mrrrors blur and the vi· bration that works its way through the seat, pegs, bar and tank as the revs climb becomes impossible to ignore .

We identity the fairly high-amplitude, medrum-frequency vibration as a rock·

All these features may well trp tho scales in favor of the Honda when it

through the rpm range. We averaged a frugal51 .7 mies per gallon in our test· rng, with a fuel capacity of 3.3 gallons, the VT should easily cover t50 mUes before the fuel level warning light glows red. The petite tank doesn't hold all the fuel; a small interconnected auxirary tank hides under the seat. The Honda holds a number of addr· tional labor-saving devices that make the Shadow almost maintenance-free. In addition to the automatic valve-lash adjustors, camchain tensioners and hy· draulic clutch, the VT750 has a point

ing·couple imbalance-the inevitabte

less •gnition, a brushless generator,

trade-off wrth this particular system. Our Shadow's carburetion was spot on. Cold startrng was hassle-free and there were no glitches or staggers

and shaft drive. Only the spark plugs, eng•ne oet and filters require attenhon; no motorcycle has ever offered such hassle-tree ownership.

comes time to buy a custom-style mo· torcycte. Anyone who buys a Shadow wiU, we think, do so on the basrs of its radrcal looks and in sprte of rts radrcal ergonornrcs and cornpromrsed versatrt· rty. It is precisely this cornpromrsed versatitrty that we find troublrng, because as a functional motorcycle the Shadow offers no better performance than what Honda believes the target audi· ence need s. That's distressing be· cause historically Honda has boon such a strong engineering companyand it still is- and it cont1nues to build a host of motorcycles devoted to func· Iron. We like motorcycles wrth almost decathlon broadness; but here Honda has grven us a beidy·buildrng cham· pron. The Shadow guy probably won't be troubled by this show-time narrowness. this compromised versat1llly He probably won't want to be bothered wrth hrs motorcycle's workrngs and is httle concerned abou t Its ultimate per· formance potential. For this guy, the Shadow Is a suitable motorcycle-tow on maintenance and high on M1lwau· kee style. We won't hazard a guess as to how many enthusiasts w1U go for Horida's radical new VT; we win say unequivocally that anyone who does choose the Shadow is sacnlicrng performance tor aesthetics. •


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