Cycle News - Archive Issues - 1970's

or Going Half-Hauig into speedway racing By Lane Campbell It's one of those "They said it couldn't be done" projects, but as the crew at Jim Wismer's Harley-Davidson Westminster co n tem pla ted mechanic Denis Porter's Jawa/ESO speedway bike, the feeling grew - they could do it: cut a 1000cc Sportster engi ne in half and make it fit in the speedway fr ame. Even (fingers crossed) provide a co mpet itive American-built alternative speedway power unit. Far out id ea ? Maybe, but this shop is no stranger to far out projects. They set up Larry Bornhurst 's Baja record Sportster last year. They had a 1973 Sportster engine, an d shop owner Wismer decided "hang the cost , let 's do it . " After months of planning, trial fitting, parts matching and careful machining, their "impossible project" looks as if it were designed that way. Getting th ere was half the fun . Here 's how: 8 The greatest plansof mice and men . . . Fitting and gearing Denis Porter (who will ride the bike in Division Two next season) made up a set of engine plates to carry the engine and the J awa gearbox in a rigid unit. The crankshaft end is splined for a floating Jawa drive ~--~z o ~ > S U Engine Burkhardt Engineering d id the case cutting and heavy ma chining, taking awa y the gearbox casing and everything aft of the rear crankcase wal l. The rear cylinder is gone, and the front cy linder operates with a rear rod, using a center spacer in the split big-end. An MC 10.5: I forged piston to ps off the reciprocating pieces. Weld craft relocated the intake tract to pl ace the carburetor on the left side, and Denis Porter made a flange to accept an S & S drag bike car b th at is little more than a humongous velocity stack with a butterfly valve and a float bowl a ttach ed . Tuner Tim Marks expects to run about 20% nitro in a methanol base with this carb o "It would be possible to run 90% nitro through this thing," he says, "but th at would be cheating a bit . . . " Jerry Branch did the fin al chamber shaping on the heads. The valve train is o ff-shelf, XLR valves, Burkhardt Engineering pushrods, and a Sifton carnset , using two of four lobes. The re ar ca m drives are still fun ctional - the rear in ta ke cam drives the magneto (a turned-around Sportster unit with a modified baseplate. single rotor and single lead cap ), while the rear exha ust camdrive is fL.l ed with classified materi al. Tim Marks isn 't letting on how he modified, blanked off and re-routed the Sportster's lubricati on and breathing pas sages. h's hi s secret of making the V-twin work like a single without pumping all its oil overboard. Oil is recirculated through the fr ame. on the engine. Yet to finish the primary chain shoe, some mods to the primary case cover, a rider's leg shie ld (if needed) and a spray shield to guard the carburetor air horn. It fired up q uickly in the shop parking lo t, and with Denis aboard, grinning ear-to-ear, it came on as a smooth and st rong runner . Extensive track test ing is st ill to come. "None of that polluting total-loss for us ," says shopowner Wismer. Edelbrock ligh tened and re-balanced the crankshaft to 60 % of recipro cating weigh r, The crew has had several flywheel sets made up in different weights to tailor power delivery for _d ifferen t track condit ions. Of course, a special blanking plate had to be ma de for the rear cylinder hole (it carries two breathers with Filtron sock type filters) . Both ca m drive side an d primary drive side covers are special items. III ..J "' 'c"r 1: u > III III o ~ o .._ - - - - -- - - - - - - - _.. ! Cut-ou ts for b ig kids. hub, so that th e j awa primary spr ocket sets can be used. This was done to take advantage of available quick-change gearing. A Sportster ch ain shoe controls primary chain tension, so the gearbox can he mounted rigidly (adding to th e frame stiffness) and so primary gearing ca n be changed without disturbing the rear chai n. U\Ve figure with this set-up, we can change gearing faster th an any body ," Den is says . " Plus with th e gearbox rigi d in th e frame , we don't have cha in dri ve power lo sses due to fra me flexing. " There's a h ead brace fo r adde d engi ne support and rigidity. When Cycle New s viewed it , the project was virtually co m ple te , with a co up le of tri al runs alread y "We had ho ped to get it ready to ru n the Ascot half-mile, but now we've got all winter to de-b ug it and get it righ t;" Even with the waiting to get all the needed parts together, Jim Wismer is stoked, as is the rest of the crew: rider Denis , tuner Tim, and pitman Joe O'Day. Denis is hot to try it out next season . He 's had several good seasons of Class "C" style racing at Corona, and figures speedway ought to be a blast. Tim is enthusiastic about the horsepower potential. "There's no way that the ESOs can run the size valves we can, or the size carb, and they haven't got as good a chamber design as we have. I've been thro ugh the Jawa - it's a good engine, but it's limited." Wismer, who has bankrolled the project to the tune of some 54000, feels that if the ha cksaw Single proves competitive, he 11 get his money back. "Burkhardt has already developed production tooling while they were doing this one, so if any th ing broke, we could be repaired and out next week. We can, if we want, mak e up a basic kit so a customer can set one up to his own specs." He's stoked on the idea of a market for an American-made speedway engine (a "Buy American" fervor pervades the whole shop, naturally) . Sin ce much of the equipment they 've used takes advantage of the existing network of drag bike parts suppliers, limited production is not as blue-sky as it would seem . With he lp and advice from Ed Schafer at Speedway Research and Specialties, they've got a way to go in learning to ma ke the bike competitive. The iron-barrel engine is significantly heavier than the ESO, weight distribution will be different, top-h amper will be different, and its handling responses will have to be learned from scratch . Keep an e ye o n the Division Two tracks aro und Southern Cali forn ia for th e racing debut of th is interesting an d ambitious project bik e. Their learning process ma y be long - pain fu l even - but it will never be dull. Not for th is crew. Their kind of enth usiasm doesrr'tcome easy . •

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