Big-Time Racing On Small-Scale Bikes
Big-Time Racing on Small-Scale Bikes
Mini-roadracers and their machines
AS WITH ANY GP FORMULA, THE RULES GOVERNING THE California Mini Road Racing Association’s 80cc GP class promote variety in machinery. The following are just a few examples of the bikes and racers Team Cycle World's KX80 confronted on the track.
Sherri Lyons
YAMAHA TZR8OR
Mini-roadracing is still predominantly a man’s world, but Sherri Lyons is winning >of that women can com-
pete, too. The 19-year-old from Lake Elsinore,
California, started racing Yamaha YSR50s in 1991 and soon established her abil-
ity to run up front. Three seasons on stock, modified and Formula 50 YSRs gained Sherri
several top-three rankings in season class points and an Amateur Modified class championship.
This year Sherri moved up to the Expert 80cc GP class. Her father, CMRRA President AÍ Lyons, built what they call a TZR80R, which is based on a ’91 Yamaha TZR50R imported from Japan. Lyons swapped the 50cc motor for a ’91 YZ80 motocrosser’s engine built by Mark Richards Racing Technology in Riverside, California. The chassis has also been upgraded with an Öhlins shock and Posh rearset pegs. Since the time of this photo, a complete Honda RS125 front end-fork, brake rotor, caliper, 17-inch wheel-and a JLF braced aluminum swingarm have been fitted. A custom-built pipe by T.C. Exhaust and Air-Tech bodywork round out the mini, which Lyons estimates is worth about $3200.
Why not follow standard practice and slap an 80cc motor into a YSR chassis? Simply put, the YSR’s 12-inch wheel diameter is too small to offer the level of steering feedback and chassis stability we were after.
Wheel size is also the reason for selecting the Kawasaki KX80 over an 80-class Suzuki, Honda or Yamaha motocrosser. Unlike other 80s, which only come with 14inch rear wheels, Kawasaki’s KX80 is also available in a Big Wheel version with a 16-inch rear. Although both KX80 models have a long enough swingarm to accept a 17inch-diameter wheel and road tire without interference from the arm’s crossbrace, we chose the Big Wheel for its stout cartridge-style upside-down fork.
Staying with 16-inch hoops was an option, but our decision to go with 17-inch wheels was based on the availability and selection of race tires in that size, including current 125 GP rubber.
Still, finding suitable rims of the proper width wasn’t easy since the KX80 wheel hub uses 28 spokes rather than the common 32and 36-spoke patterns. Buchanan’s Frame Shop provided the best solution we could find for the front. Its wheel specialist laced a 2.75 x 17 extruded-aluminum Sun Rim to the KX hub. The 2.65/3.25-17 Dunlop KR149 roadracing slick we’re using calls for a 2.5-inch rim, but we haven’t noticed any ill effects caused by the wider wheel. At the rear, a Kosman Specialties 3.5 x 17 extruded-aluminum Akront rim carries a 110/65R17 Dunlop KR106 radial slick.
In stock MX form, the KX80 has nearly 11 inches of suspension travel at each end of the bike, too much for a roadracer, so our next task was lowering the bike and firming the ride. Lindemann Engineering was called upon to handle the modifications to the stock suspension components.
Fork-tube extension was reduced 5
inches by installing a 5-inch aluminum spacer into the cartridge. Lowering the front in this fashion-as opposed to simply pulling the fork legs up in the triple clamps-not only looks better, but provides a more rigid fork due to the increased overlap of the stanchion and slider. The stock springs were shortened to obtain a stiffer rate and valving was altered to better suit roadcourse conditions.
Lindemann also installed an adjuster screw into each fork leg to control both compression and rebound damping. The adjuster is accessed with an Allen wrench after removing the air-bleed screw from the fork cap.
Similarly, a 1.2-inch spacer was installed into the fully adjustable stock shock, lowering the bike 4 inches at the rear. Lindemann also revalved and rebuilt the shock. Through test riding, we settled on a 350 pound/inch spring for our 150-pound rider.
Next on our agenda was upgrading the KX’s front brake. To keep costs down, we made use of the stock master cylinder and caliper. The stock stainless-steel rotor, however, did not perform well under roadrace conditions, overheating and warping when subjected to such abuse.
Increasing the rotor diameter in conjunction with fitting Galfer Kevlar pads gave us the improvement we were looking for: greater power, feel and resistance to fade. Kosman Specialties machined an aluminum center to adapt its floating 10.0-inch cast-iron rotor to the stock wheel hub. Minor machine work on the hub’s flange was required to provide clearance for the bolts that fasten the rotor to its carrier.
To achieve more of the look and feel of a roadracer, we bolted on AFAM’s M5-Works Superbike handlebar, made of 5mm-thick, 7/8-inch aluminum tubing with a titanium color anodized finish. Other finishing touches: a customlength braided-steel brake line with protective vinyl sheathing, a custom front fender via hacksaw, and a new Ceet Kevlar Dynotec seat cover (complete with silkscreened Cycle World logo on the sides).
We were now official and ready to race.
Prior to our racing debut with the Team CW KX80, many in the mini-roadracing fraternity believed that bikes with small, 12-inch wheels were unbeatable on cart tracks. But we may have opened a few eyes with Road Test Editor Don Canet’s success. He remains undefeated in the Expert 80cc GP class after eight sprint races. In the process, Canet and the KX have set the fastest lap at each of the three tracks we’ve raced.
In a test of the bike’s durability, Canet teamed up with former racer Greg Tysor for a two-hour endurance race at a cart track in Phoenix, Arizona. Team Cycle World convincingly topped the field, winning by six laps. “In my entire racing career, I’ve never had such an equipment advantage,” said Tysor.
Our first few victories were achieved running a stock motor. In the name of easier wheelies and further development, we sent the head and cylinder off to FMF Racing. An FMF Gold Series pipe and silencer were bolted on, along with FMF-ported cylinder, reworked head and FMF Quick Rev reeds, delivering a noticeable boost in midrange and top-end power with the rev range extended up top.
Chris Ulrich
MORIWAKI MH8OR
Chris stranger Ulrich, to the 14, world is no of motorcycle roadracing.
But the youngest son of racing journalist John Ulrich didn’t turn a wheel on the track until last year when he went racing on a stock YSR50.
In the beginning, it wasn’t all trophies and roses for the Lake Elsinore teenager. “I fell down 21 times on 50s,” says Chris, who suffered a broken arm in one of the shunts. Before long, however, he was clearly on the fast track, tallying a number of 50cc Beginner-class wins.
Ulrich graduated to 80cc racing eight months into his budding career and is now well on his way to winning a CMRRA Amateur 80cc GP Championship.
His $3500 bike, developed for Japan’s popular GP80 class, is a Moriwaki MH80R, basically a Honda NS-1 streetbike chassis modified to carry a CR80R motor. A Moriwaki exhaust pipe, aluminum fuel cell, rearsets, clipon bars, fiberglass bodywork, tachometer and water-temp gauge add a professional look. Additional mods include a Fox Twin-Clicker shock, mild cylinder work and Team Valvoline paint scheme.
Recently, Chris competed in a round of the WERA F-3 National Series aboard his father’s Honda RSI25. He’s since become a strong advocate of big-wheeled minis, calling the 17-inch Moriwaki MH80R an ideal 125 trainer.
SUPPLIERS:
AFAM USA
5953 Engineer Dr.
Huntington Beach, CA
92649
714/379-9040
M-5 Works handlebar: $40
WorksLite rear sprocket:
$46
Countershaft sprocket: $6
BUCHANANS
629 E. Garvey Ave.
Monterey Park, CA 91754
818/280-4003
Front wheel: $244
CEET RACING PRODUCTS
1220-B Liberty Way
Vista, CA 92083
619/599-0115
Seat cover: $70
DUNLOP TIRE CORP.
P.0. Box 1109
Buffalo, NY 14240
800/828-7428
Rear KR106 slick: $149
Front KR149 slick: $105
Rear KR444 rain: $160
Front MR677 rain: $149
FMF RACING
25933 Frampton
Harbor City, CA 90710
310/539-6884
Head and cylinder modifi-
cation: $250
Gold Series pipe: $170
Silencer: $70
Quick-rev reeds: $30
GIOCAR AMERICA CORP.
104 San Federico Ave.
Santa Barbara, CA 93111
805/967-2726
Galfer brake pads: $43/pair
Brake line: $58 front
KOSMAN SPECIALTIES
55 Oak St.
San Francisco, CA 94102
415/861-4262
Rear wheel: $285
Front brake rotor: $275
Caliper hanger: $50
LINDEMANN
ENGINEERING
520 McGlincey Ln. #3
Campbell, CA 95008
408/371-6151
Fork modification: $220
Fork rebound damping
adjusters: $90
Shock modification:
$155
Shock spring: $90
Kevin Sheafer
YAMAHA YSR/RN8O
he high cost of racing big bikes got to be a bit too much for Kevin Sheafer when two seasons aboard a FZR600 and an EX500 at
Willow Springs Raceway netted a Lightweight Twins Championship but very little in the way of sponsorship. So the 27year-old
from Escondido, California,
decided to scale back his program.
Since getting into mini-racing mid-season of last year, Sheafer has found more than just cheap thrills at the cart tracks. Late start and all, he finished second in CMRRA points last year, riding YSR50s in the stock, modified and Formula 50 classes. This year, he took the Expert 80cc GP Winter Series title.
Sheafer’s preferred weapon is a ’90 Suzuki RM80 motor in a Yamaha YSR50 chassis. Key aspects of the 80cc conversion include a lengthened swingarm, Works Performance shock, standard YSR fork mods, routing the RM pipe out the tailsection and mounting the RM radiator. Sheafer figures $2000, with good buys on used equipment, could put you onto a similar bike.
He hopes to land a 125cc ride sometime soon. Until then, Sheafer keeps his riding skills sharp and spirits high racing with the CMRRA. “It’s fun,” he says of the 80s. “You work on ’em, prep ’em to get ready for the race weekend, then come out and have a ball.”
Kawasaki had a 99cc big-bore kit for the KX that included a Nikasil cylinder, piston, rings, wrist pin and gaskets (it will offer a KX100 in ’95, so the kit has been discontinued although the individual parts are still available). We nabbed one of these $342 kits and let FMF add boost ports to the cylinder and a window in the piston skirt. Definitely the ticket to wheelie heaven!
Sure, kick ’em when they’re down, you’re thinking. Naw, we just needed a stronger fix. After all, speed can be addictive. Now, if we can get promoters hooked on the idea of adding a 105cc GP class.
Only time will tell whether this type of bike catches on with the mini-roadracing crowd. We have clearly demonstrated the bike’s worth by stealing the show and the tallest trophy wherever we’ve taken it. There has been a bit of grumbling in the ranks about our larger wheels offering an unfair advantage. Maybe so, but where would full-scale GP technology be if no one ever gained an advantage working within the rules?
We think of this bike as a Minimoto, a scaled-down version of the half-dirt, half-street Supermoto racebikes that have become the rage in Europe. It would make an ideal training tool for an ambitious pre-teenager following in the footsteps of Roberts, Lawson, Spencer or Rainey-each of whom honed their skills on dirt-tracks prior to winning multiple 500cc world roadracing championships. Think of it, dirt-track on Saturday night, roadrace on Sunday-all on the same bike. □
For more information about class rules and race schedules, contact the CMRRA at 15023 Valencia Wav, Lake Elsinore, CA 92530; 909/674-5357.
Hikaru Miyagi
HONDA BAJA MONKEY
hat’s a former 500cc rider doing in mini-roadracing, a sport viewed by many as stepping stone or budget racing? Giving the two-stroke riders a run for their money a $10,000 jewel of a Honda Z50, is what.
Up until a few years ago, Hikaru Miyagi rode a works Honda NSR500 in the AllJapan 500 GP championship. In 1991 he suffered serious injury in a streetbike accident, ultimately costing him the factory ride. Now the cheerful
31-year-old from Osaka, Japan, is on the comeback trail, racing here in the states for Erion Racing in AMA national competition.
When Miyagi isn’t aboard Erion’s CBR900RR and CBR600 racebikes, he can be found tinkering with his Baja Monkey, a limited-edition version of Honda’s venerable Mini-Trail. Built to 106cc, Miyagi’s racebike is chock full of beautifully crafted bits from Takegawa, a Japanese company that specializes in hot-rodding the Z50. Only the frame, bodywork and engine cases are stock; virtually every remaining item comes from Takegawa and is now available in the U.S. through Two Brothers Racing.
When asked if riding the Z50 is an integral part of his return to racing, Miyagi says with a smile, “Racing the Z50 is my hobby and very fun. Both need the same kind of concentration, so in that way it is the same.” -Don Canet
