Cycle News - Archive Issues - 1970's

Ab ove: What y ou 're seeing is a "p lug" - a fu ll-scale master bod y mo ld for Bob Geo rge's streamliner, and where it was built. Bob retains th e full-tap er tail, rejecting " Kamm Th eory " cu tof f, in hopes of avoiding stabili ty problems. Rear of tail will jettison to slow down, pulling ou t the f irst drag chute as it goes. Pair of deuces with a long tail By Lane Campbell Last summer, the newest member of th e Bonneville 200 mph club , Dave Campos, cracked the barrier not once, but twice, setting a pai r of records in the process (CN Sept. 24 , 1974). The partial streamliner he rode had two unblown Harley 74 V vtwin engines and looked li ke what Ge or ge Barris might have done to a cafe racer. The o w n e r /b u i lder o f the double H arley, Bob George o f Hawthorne, California , became so enthused with th e power potential he wa s holding, he began to think "why not go all the way ?" Yamaha MX400 (Con tin ued from page 25) . do es happen the fir st sign of it is a problem down sh ifting. The o ther problem wa s wi th th e premi x o i l. The own er's manu al rec o m mends a 20 : 1 Castrol blend with premium gas. While we were chec ki ng ou t th e shift screw prob lem Kasson pulled the head an d found ex cessive carbon buil du p th at would h ave re sulted in stu ck rings b efore t oo lo ng. This was with less than three hours on the engin e. Rid ers unfamiliar with Castrol told us we were runnin g it too rich and th at they had run up to a 3 2 : 1 mix without an y ill effects. A call to Ya maha In te rn ati on al brou ght a rec omm end at i on f r o m the racin g department to run Pennzoil 24 : 1 an d if that wasn 't available to run Torco 5 0 a t the same rati o . For so me reason no on e said to u se Yamalube, Other than the shi ft screw hassle the gear b ox performed flawl essl y with light switch quick shifts ei t her up or down the e x c ellently sp aced ratios. The en gin e/ gear bo x unit coupled wi th the smoothness o f the carb /reed valve set up is the main attrac t io n of the MX 400 despite its advanced suspension de sign . In the end result the Monoshock is prob a bl y a s effective as the new cantilever systems fro m Europe with the dis advan ta ge of hav ing excess wei ght high in the frame. What makes th e monoshock sys tem important is its alm ost inde structabili ty, th e variatio ns possible for th e ind ivid ual ride r, and being a new applicat io n of a design th at dates b ack to the Vincent. Bits and pieces Dr oppin g the front for ks down in th e yo kes to YZ specs resulted in a sligh t im pr ovem ent in str aight line stab ility but ca used the front end ,to flex more while co rnering. Th e stock I po sit ion . marked with a cut on eac h for k leg, wo rks ou t th e best for all ar ound use ... DID rims were up to their usual ex cellence and we ex perienced none of th e so ftness others have no ticed of lat e Left: Partially -comp leted fr ame with " mo ckup " engines in place to get f inal dimensions of engin e m ou nt plates. There 's ro om in the engine bay fo r blow ers - later. if un blow n engines d on't m ake th e ne cessary ho rsepo we r this year. All the wa y to a Bonneville biker means the absolute Land Speed Record fo r two-wheeled vehicle s wh ich Don Vesco cam e within a te chnicality of s e itin g last seas on . The long-tailed Ia y back full streamliner which Bob Gr een e is building (litera lly) in his bac ky ar d is intended as a full assa ult on t h at re cord (which still stands at 265 .4 92 mph , hel d by the late Cal R a yborn) , S in c e Bob's pa r t i a l streamliner, none too "clean." a shape at be st , set a 23 1.59 7 mph record o n fuel , Bob feels th e full 'lin er , with just a bit more power, has a sh o t at it. Power will come from a pair of wat ercooled Harley "74" en gines (usin g w at er j a ck et s w hich Bob, a p atternm aker b y t r a d e , des igned himself), usin g the late st design S & S in m aterial .. , th e radial h ea d and cy linder ar e bl ack with buffed edges and l o ok s g r eat sam e for th e black en gine Cases if yo u run in muddy weather, remove the co unte rshaft cover as it gets clo gged up imm ed iatel y . . , cases a r e m a gn esium lik e the YZ . . . white paint job looks good at first, but is eas ily st ained by p re-m ix splash .. . tan k ca p and fille r is t o o sm all and h ar d t o fill , , . tank de sign is best describe d as a fat YZ and ke p t riders' legs wide enough to almost clear the bulbous pi pe th at arches u p , over an d around t he cylinder head . . . seat is ab ou t one to tw o in ch es smaller overal l than the YZ , an d t he padding feels harder . .. fro nt and rear fenders ar e pl as t i c a nd s u rvived repeated so il sa mpli ng . .. small sile ncer d oe s a co m mendable j ob o f q uie ti ng ring ding st i n g . . . the ex pansion chamber is much bet te r mounted than the YZ unit with two sprin gs, o n e spring lo aded nut jb olt, tw o ru bber vibration dampers , one sp ring to the fram e, tw o bolted brackets an d a hos t cla m p on th e silen cer .. . still not a bad idea t o chec k ti ghtness of rubb er h ose con nec t ing air bo x and carb . . , black co n ta ct pap er on numb er plat e s w en t s o ut h in a hurry ... b ars ar e t o o wi de for most people but ar e o f sa tis facto ry bend . . . usual YZ kill bu tto n , alloy levers with dust co vers and quarter tu rn throttle . .. grips were of co rr ec t d esign bu t of the wron g mat eri al . . . rear chain adj us t ers should be ch anged for sturdi er st eel enduro m odels . .. a very handy si de st and i s s ta n da r d e q ui p men t . .. d ish ed o ut b o lts and othe r wei ght saving me asu res ab ou nd on th e bike . .. two b olt s h old th e seat in place and o n~ b olt and two ru bb er g ro m m e ts h ol d t he t a nk sec urely . . . front forks p rovided pl en ry of cus h , but so me riders have ad de d Te rry kit s to theirs and cl aim better performan ce. To tal ed up, the MX 400 is one he ll of a m ot or c y cl e arid t he st r ongest co mpeti t o r fo r th e YZ do llar. If y ou are really in to the YZ m ys tique yo u can always buy the yello w tank, fenders an d t h icke r seat and real ly blow so me minds. - August, , . I hope we get to go to EI Mirag e and test - get all that fal1ing over sideways done with there and ac t ua lly do so me th ing during the Speed Week . .. D a v e Campos will again do the driving, and will use th e sh ak edowns t o get used to a " lay d own" ride. Asked about Har ley factory help, Bob sai d "Nope. Not yet , maybe late in t he game. Fran kly I di d n 't know how many co n tingen cies were available unt il I t alked to Dennis Manning (of the Norton effort) abo u t it . " Lookin g at t he flawless surface of the body m a ster , ' f e e li n g it s silky s moo t h ness with the fmge rtips and l i s t eni n g t o Bo b George 's straight n o-n on sence mechanical approach, we sense t hat if the effort falls sh ort, it won 't be for lack of workmanship or de dicati o n , eithe r one . _ R ight: Last of the all-out Back y ard Sp ecials? It fuel carbu ret ors. S & S, wh ich is picking u p partial spo n sors hi p on the project, will build four co m ple te engines so Bob will have a spare set ready when he hits the salt this summer. "Performance Mac hin e is kicking in a lot o f time on this, " Bob told us, " and there 's at least six guys who 've been com ing over to vo lu n t eer their ti me. I can 't begin to count the hours we 've go t in so far." "We 've go t the main ch assis stru cture do ne and are abo ut finished with the cen ter-h ub st ee ring. The fiberglass plug (maste r mold) y o u saw is done and ready t o start cast ing th e b ody m olds. Looks like we 'll have it ready in Specifications • • • • • • • • • • • • • • • • • • • • • • • • N/A=lnfo not available 0 = 00es not ap ply to this model * =A vailable from Yamaha Part s Distributors, Inc . MODEL - IBM I,D, NUMBER Start ing Eng ine and Fram e N umber MX400B 510-000101 Buie Colo r (fuel tank) Wh ite/C om peti tion Ye llow Ne t WeIght ENGINE Bor e 2281bs. (wee . indu ct ion Str oke 51 0 C~ syste m ) hoder 2·stroke Aeed V alve Sinnle A ir-cooled D ispl ace men t 397 cc 124,22 CIDI 7,57 :1 Piston Sk irt Clearance (new/ max,) ,05 5 - .0 60 mm /.0022 - ,00 24'"" 0 ,1mm I ""4'"' Ring End Gap (top/2 nd/ 3rdl 0 ,4 - 0 .5m m /.0 16 - ,020 " ' lS ameld> R ing G roo ve Clearance (top/2nd /3rdl ,OS - .09 mm 1002 - oo4 '"' IS.meld> Va lve Cle arance (eng . col d ) Intake/E xhaust d> AUTOLUBE - Mi nimu m Pump Str oke/ Color Cod e cb [E n qine tubed bv 20 :' Premix) CARBURETOR (mfr) {rv pel tl .D. number) M ikuni VM3BSS 5iOOO Main Jet No . 350 Needl e Je t P-4 Jet N eed le/Cl ip Po sit ion 6F16-4 Cut Away 3.0 Pilot Je1 No . 60 A ir Jet N/A Sta rter Jet No. SO A ir Screw (t urns outl 1.0 18 .0 ± 1.0 mm Fl oat Level J( 'C 85 x 7Qm m x 1 Compression Ratio Air f ilt er (type x quantity) Wet Fo am Rubber x 2 O il Ta nk or Engine Sum p 64n4 2.667 H elica l Gear DK520T, 105L 50114 3.57 1 21 .429 36/16 2250 32/1 9 1.684 16.040 29/23 1.2 60 t2.008 26/2 6 1.000 9 .524 23/29 0.793 7.55 3 d> l .ooocc 133.8 oz .I 5AE10W30 Oil (Yamalube a-cvcrel d> Fu el Tan k 2 . 1 aal s. Prem ium (Pr em ix 20: 1) DRIVE - Prim ary (tYpe) ( teeth ) (rat io) Seco ndary (ty pe) ( tee t h) (r at io l Transmission Rat ios 1st (t eeth) (rati o) (O .A.) 2nd 3rd .eth 5th 6th CAP ACITIES - Trensmisslcn Fron t Fork s tsc.sce 16.4 oz.I 20 Rear Sho cks (MONOCR OSS) 2 75cc (9 .3 Tires (size/nom inal pressure) Fr ont : 3 .oo ·21 / 130si ELECTRICAL - Charging Sy stem (mf rl It vpel M itsubi shi No Load Vo ltage Ad j . (A C & DC generators) Rear : M.ax. !iene rator (M agneto) Output . ... .,. .. . . -. . ~ -. , ~ ..... . - - 1.02n . 6.0Kn --- -

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