Funny front end…

The odd­est ball of all

Classic Racer - - WHAT’S INSIDE - Words: Alan Cath­cart Pho­tos: Phil Masters

The Bi­mota Tesi YB wasn’t what you’d call suc­cess­ful out on track, but as a piece of track-in­spired en­gi­neer­ing it de­serves its place in the an­nals of his­tory. Not just for the clev­er­ness around the whole bike but the sheer au­dac­ity of that front end…

Tesi means ‘the­sis’ in Ital­ian, and that’s how Bi­mota’s re­mark­able al­ter­na­tive mo­tor­cy­cle started out, as a com­bined ef­fort be­tween the com­pany’s then-chief de­signer Federico Martini, and two Bologna Uni­ver­sity post­grad­u­ate stu­dents, Roberto Ugolini and Pier­luigi Mar­coni, who spent six months dur­ing 1981-82 work­ing in the Ri­mini fac­tory as part of a work/study pro­gramme. The hub-cen­tre Tesi de­sign they cre­ated there, based on a Kawasaki GPZ550 en­gine, rep­re­sented the de­sign the­sis for their Imeche me­chan­i­cal en­gi­neer­ing doc­tor­ate course, and their uni­ver­sity’s com­puter was em­ployed in the pre­lim­i­nary de­sign work, on what was the world’s first mo­tor­cy­cle with hy­drauli­cally-op­er­ated cen­tre hub steer­ing. The first run­ning Tesi pro­to­type ap­peared soon af­ter Mar­coni joined Bi­mota full-time in 1983 and was the fo­cus of much at­ten­tion when it was un­veiled at the Mi­lan Show that year. Pow­ered by a VF400 Honda V4 en­gine, the Tesi 1 was a street bike that cov­ered sev­eral thou­sand kilo­me­tres on the roads around Ri­mini as a rolling test­bed, be­fore end­ing up as a static ex­hibit in the fac­tory lobby, when it was su­per­seded by the Tesi 2. This also em­ployed a V4 Honda mo­tor, but one of an en­tirely dif­fer­ent na­ture – a full-race 750cc Honda fac­tory race en­gine pur­chased di­rectly from HRC for en­durance rac­ing in the TT F1 class, in which the rad­i­cal Bi­mota made its de­but at the Aus­trian round of the World En­durance cham­pi­onship in June 1985 in the hands of de­vel­op­ment rid­ers Da­vide Tar­dozzi and Mau­r­izio Rossi. The in­evitable teething trou­bles man­i­fested them­selves be­fore Rossi’s spec­tac­u­lar get-off that fi­nally side­lined the bike. It next ap­peared in Septem­ber’s Ital­ian En­durance ti­tle round at Misano, when it went much bet­ter… un­til a valve dropped in the Honda en­gine.

The first Vf400-pow­ered pro­to­type de­signed by Martini with Mar­coni’s as­sis­tance had em­ployed a box-like chas­sis, made from sheets of al­loy-faced honeycomb M-board by CIBA-GEIGY, glued to­gether to form an ul­tra-strong struc­ture with a high stiff­ness to weight ra­tio, like the con­tem­po­rary Heron-suzuki 500GP racer em­ploy­ing a sim­i­lar frame. How­ever, the VFR750R Honda F1 en­gine was too bulky and, es­pe­cially, too tall to per­mit this type of so-called card­board box de­sign on the Tesi 2, which there­fore fea­tured a twin-spar frame in car­bon-fi­bre honeycomb com­pos­ite. The en­gine now acted as a semi-stressed mem­ber, sus­pended from the frame, which weighed just 5kg com­plete, less the swingarms. That’s plural and not sin­gu­lar, be­cause Mar­coni re­placed

the front fork on the Tesi se­ries of bikes with an ar­tic­u­lated par­al­lel­o­gram cen­tre-hub de­sign, dubbed the DSC or Drive Con­trol Sys­tem. WhileWhil on theh Te­siT 1 the front Mar­zoc­chi suspension unit had been lo­cated hor­i­zon­tally be­hind the front wheel and partly be­neath the en­gine, on s sub­se­quent ver­sions this was mounted ver­tica ally with a pro­gres­sive link, sim­i­lar to that em mployed at the rear of the bike. Rather than mou unt­ing the twin front swingarms in par­al­lel on the e same side of the wheel, these were hor­i­zon­tally y op­posed to each other in or­der to give the e more than 30° steer­ing lock nec­es­sary for st treet use. A pair of tie rods al­lowed the trail – no less than 120mm to com­pen­sate for what Martini per­ceived as an in­her­ent lack of s sta­bil­ity in cen­tre hub de­signs, cou­pled with an ul­tra-steep 20° ef­fec­tive head an­gle – to be var ried al­most in­fin­itely, while there were auxil iary brake and steer­ing links. Con­tin­ued pro oblems with the Honda race en­gine rather th an the Tesi’s rev­o­lu­tion­ary chas­sis re­duced d the Tesi 2 en­durance racer’s pub­lic out­ings to o a hand­ful, though it was tested ex­ten­sive ely in pri­vate through­out 1984/85. At this point, Martini was ready to move to the nex xt stage of de­vel­op­ment and the Tesi 3, with a tubu­lar steel space frame, ap­peared at the 1985 Mi­lan Show. This could be more eas­ily adapted to se­ries pro­duc­tio on for street use than the ex­pen­sive carbo on-fi­bre chas­sis, and test­ing be­gan the fol­low wing year, still us­ing the trou­ble­some V4 Honda en­gine. Martini’s Tesi 3 de­sign es­tab­lis shed the tem­plate for fu­ture Tesi mod­els, al­beit re­tain­ing his favoured hy­draulic steer­ing. But Bi­mota’s suc­cess in World Su­per­bike rac­ing with the Yamaha-pow­ered YB4EIR slowed the Tesi’s de­vel­op­ment, and early in 1989 Martini moved to Gil­era, leav­ing Pier­luigi Mar­coni to as­sume the mantle of Bi­mota’s chief en­gi­neer and he re­gained con­trol of the Tesi project that he’d been re­spon­si­ble for con­ceiv­ing in the first place.

Jet­ti­son­ing the Tesi 3’s boat-de­rived hy­draulic steer­ing in favour of a me­chan­i­cal sys­tem, Mar­coni had an all-newybtesi pro­to­type run­ning in­side just two months, now fit­ted with a Yamaha FZ750 en­gine, but em­ploy­ing the same es­sen­tial ar­chi­tec­ture as the Tesi 3. This, in turn, led the fol­low­ing year to the Du­cati-en­gined Tesi 1D that, af­ter a sea­son of rac­ing in the Ital­ian Su­per­bike se­ries pro­to­type class, was launched as a se­ries pro­duc­tion street­bike at the Oc­to­ber 1990 Cologne Show. Over the next three years, 417 cus­tomer ex­am­ples of the var­i­ous Du­cati-pow­ered Tesi mod­els were built, in­clud­ing 51 fit­ted with the 400cc air-cooled desmodue mo­tor for sale in Ja­pan. Pro­duc­tion of a model that had rep­re­sented a per­sonal voy­age of dis­cov­ery for Pier­luigi Mar­coni ended in 1995, and in­spired a cult of like-minded be­liev­ers who bit­terly re­gret­ted the Bi­mota man­age­ment’s de­ci­sion to axe the high-pro­file, but also high-priced, low-vol­ume model.

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