Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/128085
Project Bike By Scott Rousseau Photos by Stan Han sen and Jamey Blunt ~ • g: en ,..; .2: E .. o o 28 f you have been following along as our for lorn old '76 Yamaha XTSOO has been turned in to a dirt track racer, then you're probably figuring that we're getting close to w rapping thi s pr oject up and getting it on the track. Well, for the purposes of the story line, you' re rig ht. Like I said befor e, d irt tracker s are nowhere near what is the now-standa rd package racer MX bike when it comes to pu tting the pieces togeth er. A savvy guy with a weld er, a dri ll press and a bench lathe could probably whi p ou t the necessary pieces to convert his motorcycle in a minimum amo unt of time. Ou rs sim ply . took a long tim e because I had to ferry th e machine her e or th er e in between putting in the usual am ount of work on th e n ewspaper. It go t es p ecia lly b ad when the time came to actually screw the bike together, right aro und our 1998 ed ition of eN issu e #50. The greatest singular block of time that was lost in the project was when the bike just sat still in the warehouse after the Christmas holid ay . Speed & Spo r t had delivered our chassis, w heels, hubs and a few other bits back from the powde r-coater. Matt Hil genberg of Speed & Sp ort a lso offered up a s et of ch ro me K&N di r t track bars, and a Tsuba ki chai n so tha t we co u ld ti e th e e ngi ne to t he re a r wheel. In the mean time, projec t overseer Dennis "Big 0" Voll punched out a sea t and built ou r ta nk from a Cham pionstyle mo ld that Rick Anders at Anders Racing Products had lying on the shelf. The engine had returned from Total Performance Racers & Restoration in Tulsa, Oklahoma . Our Power Pros exhaust sys- Yamaha 540 dirt tracker, part 4 (Above) Almost there: This the way our project flat tra cker loo ked just befo re heading off to Dirt Dynamics for it s fi nal assemb ly. (Below) Early track testing revealed that the fo rks were way off the mark. Further mod ification was necessary to get the front end to behave. . tem was rea dy an d waiting. But when it was time to pu t it all toge ther, it seemed like nobody had any time to spa re. Voll w a s slam med w ais t d eep in fiberglass and pa int wo rk for other custome rs, but he did take the time to lace and tru e th e wheels, thus get ting the machine up on its legs . Anders took a sho t at the buildup and at least got the engine in the chassis, but it was his busy time of the year , as he holds d own someth ing like four jobs in addi tion to his welding and fabricating business. We did what we could, bu t there were still small items that needed atten tion alo ng the way, suc h as machining va rious aluminum spacers, mounting the Airhea rt b ra ke syste m th at Jo hn ny Isaac s had supplied, hangin g the brake peda l, etc. And there we re ot her items tha t needed attention, such as the manufacture of the topout spacers for the forks. Enter Rick Doughty of Dirt Dynamics. You have no doubt seen that name quite a bit in recent editions of this publication, as well as in several others, as Doughty is the purveyor of Vintage Iron Internatio na l, which is alrea dy wo rld renowned for itsvintage and evol ution motocross bike restorations, parts and services. The fled glin g Dirt Dynamics is ac tually Dou ghty' s second co m pa ny , fou nded mor e as the mod ern bike arm of hi s Vinta g e Ir on o pe ra tio n . Dirt Dyna mics was co nceived to hand le everything from pro ject bikes to conce pt bikes, a one-off styling an d fab rication stud io if you will. To date, Dirt Dynamics has tackled projects such as one of the first installations of a Ho nda CRSOO engine into a CR2S0 aluminum perimeter frame, exotic minis and even singleand tw in -cy lin d er roa d racers . These projects all requ ire the kind of attention to detail that ou r machine so rely needed in order to ge t "trued up." . Dirt Dyna mics stra ightened out our w h eel s p ac er.s, m oun ted up a ra th e r m o to cro ss-l oo ki n g b u t n o n e th e les s extremely stu rdy brake setup, d ialed in the rear brake sys tem, mounted up our Works Performan ce shocks and Motion Pro ca b les t o t he M a gura con trols (which we re already on the bike w hen I fou nd it), installed the topouts to shorten the fork travel by a little over three inches, an d then turned us loose. When we go t it back, the machine had clearly taken a turn toward completion . All that was really left was the mounting of the carb uretor and air filter plus a few other bits , and the final fittment of the Big 0 bo dywork before we were read y for a test spi n. A word on the carburetion. Isaacs had suggested that we go with a 38mm Mikuni flat slid e u nit in ord er to coax the best power out of the bike. We contacted the good folks at White Brothers an d had them send one out to us , only to find that we could not make it fit into the intake manifold because of the bul bous oil tank /frame backbone on the stock IT. The bad news in all of this is simply that Isaacs felt our power would suffe r a bit if we had to go to a 38mm round slide. T he good new s is tha t 38 m m ro u n d s li d es can be ob tained fro m sa lvage yards for mini m u m d inero . O f course, we simply p ho ned White Brothers again and arranged for a trade. Proble m solved. It didn't take long to get the bike to fire up once it was finally all together, but getting it to run right w as another matter entirely. The motor sound ed okay jus t off idle, but it would fall flat on its face wh en it came time to really goose it. We figu red that the carbure tor was off, and swapped jets like an Ira qi fighter pilot in an effo rt to cu re th e st u m ble. With no luck, we then turned our attention to the ignition. The motor had been fitted wit h a prototype magneto that had never been tested in a working environment, and it turned out to be the culprit. We were forc ed to can the entire unit and go back to the stock points-type system, but the move made all the difference in the world . This time , the engine sounded mean, and even the slightest twist of throttle has the fr ont wheel dancing off the ground like Fred Astaire. Great. We had the power, bu t would the bike handle like it was su pposed to? Ju st as w it h th e engine, th a t was to o much to ex pect righ t off th e ba t. Vo ll and I too k the bike to Ken Maely' s hot shoe ma nor ou t in Coro na , California, to s p in so me lap s, and ri ght a way w e knew that the forks need ed mor e help . They dove un controllab ly when dri vin g into the tu rns, ma king the front end a wiggling nigh tmare. The steering was out the window, making it tough to ascerta in if everything e lse was in decent order. Back at Voll' s we tore the fo rks apart again, adding even more