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1998 Aprilia RS250 Cup BikeMSE Ratings

1998 Aprilia RS250 Cup BikeIt\'s a two-stroke sportbike. It\'s a racing series. It\'s a two-stroke sportbike and a racing series all in one.

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AddedDate Added: 8th September 1998
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Editor Contributor's Review

It\'s IROC for motorcycles. Well, maybe AROCH is more like it: American Race Of Champion Hopefuls. And that\'s it in a nut. You can\'t have one without the other; the RS 250 is available to licensed racers only and the Cup Challenge is for Aprilia RS 250s only. Sure, you might be able to get your hands on an RS 250 and never race it but I have to leave you to your own devices for that one.

Now that Aprilia has come to the States they\'d also like to get all of the gray-marketed RS 250s off the streets, so the Cup Challenge series is open to all RSs dating back to \'95. When Aprilia wasn\'t here they didn\'t have much to fear in the way of liability because if a foolish owner wanted to sue them there wasn\'t anyone around to sue. Now that they have an office here they\'re concerned about liability issues in our litigious-happy States, so Aprilia must protect itself up front. So, if you\'re riding an RS on the street you probably shouldn\'t try ordering parts from their American distribution center. Hide it or get it to the racetrack.

The idea behind the Aprilia Cup Challenge series is to offer riders a reasonably inexpensive place to race where riding, not tuning, can determine the finishing order. Modifications are not allowed. At this writing the chance still exists that the governing body of the series will even transport your bike to each event. Just show up, ride your bike, collect your money, kiss the girl, and go home.

The Racing Series

The Aprilia Cup Challenge for \'99 consists of four races run in conjunction with various racing series in the United States. Each race carries a total minimum purse of $5,000 plus whatever other contingencies might apply. The sale of the RS 250s and the governing of the Cup Challenge series will be handled by Zero Gravity, makers of aftermarket windscreens. For information regarding the series contact Richard Nelson at Zero Gravity, 310 Cortez Circle, Camarillo, CA 93012, phone: 805-388-8803, fax: 805-388-8285. Tell him we sent you, if you\'re actually going to get a bike. If you\'re just going to be annoying then tell him you found his phone number under a bush.
 

Aprilia Cup Challenge Rules

1.Get an Aprilia RS 250. $8,399 plus destination charges.
2.Put gas in it with a specific gravity of zero. No wait, that\'s the company running the events. Try gas with a specific gravity between .700 -.775. No oxygen or nitrogen bearing additives allowed.
3.Keep your meddling hands away from the engine, clutch, and gearbox.
4.And leave the ignition system alone, too.
5.And the frame too, with the exception of replacing the steel subframe with an exact design and dimensioned unit in aluminum.
6.Telemetry systems are cool but you can\'t use one.
7.If it doesn\'t say you can do it somewhere in rule 8, you can\'t do it.
8.Here\'s rule 8:
A. Carbs - can be rejetted.
B. Fairing and Bodywork - can be replaced with exact glass copies; no carbon fiber allowed. AirTech and Sharkskinz will be offering replacement parts.
C. Suspension, front forks - must be standard units for year of bike. Internals and springs may be replaced.
D. Suspension, rear shock - may be altered or replaced. Original linkage must be maintained.
E. Steering damper - it\'s a good idea.
F. Brakes - pads may be replaced with the material of your choice.
G. Brake lines - steel lines are recommended.
H. Clutch plates - plates may be replaced with your choice of brand.
I. Windscreens - aftermarket windscreens are allowed. Hmm… wonder where you could get one of those?
J. Hand and foot controls - you can alter them, whatever that means.
K. Air filter - aftermarket filters are a-okay.
L. Reed petals - ditto. What the hell are reed petals?
M. Exhaust system - likewise. You might want to give the guys at Arrow a call.
N. Fasteners - you can use aftermarket fasteners but no Ti.
O. Axles and rear brake caliper hangers - you can alter them to facilitate tire changes.
P. Any DOT tire allowed.
Q. That\'s it.
 

The Bike

The Aprilia RS 250 has a huge enthusiastic following in the States by lovers of two-strokes. It\'s Italian (sort of), it\'s an Aprilia (mostly), and it\'s a two-stroke sportbike. You can\'t ride it on the street in the States but why you\'d want to, I don\'t know. I\'ll admit up front that I\'m not a fan of two-strokes. I appreciate how the technology of two-strokes allows them to be lighter than four-strokes but what is given up in aesthetics of sound and moving parts is unforgivable. So shoot me.

The last time I rode a two-stroke machine was in the summer of \'80. It was a Yamaha RD 350 that I\'d bought used from a racer. I never could figure out what he had done to the bike\'s engine but that machine was frightfully fast. It also only got about 14 mpg on a good day and it was stinky, smokey, and…

I never liked that RD. Its speed was great fun but valves and cams and springs and shim buckets and such have an attractive aesthetic of form and purpose. Two-stroke engines are, to me, just devices with moving parts, sort of like clickable pens, vacuum cleaners, air conditioners, garage door openers, and apple peelers. Give me the romance of a complicated valve train any day. I know many who strongly disagree with me and I don\'t mean any of this to be taken as anything more than my foolish personal opinion. It\'s not right or wrong, it\'s simply my prejudice.

The Aprilia RS 250 is powered by a Suzuki liquid-cooled, two-cylinder, 90 degree V-twin. Being a two-stroke there\'s not much else you can say about the engine. The fuel mixture comes in one end of it and exhaust gases go out the other end. Two 34mm flat slide Mikunis control the mixture. On the right side of the engine is a funny little lever that I haven\'t seen since around the time that I owned the RD. If you fold that lever out and push down on it the engine actually turns over. Cool. If you don\'t want to use the lever then all you have to do is learn how to run with the bike and then jump on it without falling over. If you like electric starters you\'re out of luck.

The RS 250\'s gearbox is a 6-speed extractable unit but that last feature can only be used to amuse your friends on rainy nights. The Cup Challenge series prohibits changing internal gearing.

The frame of the RS 250 is a combination of welded beams and castings of an aluminum/magnesium mix. Today\'s versions of the bikes have an aluminum subframe so I\'m not quite sure where that word of a steel subframe ever came from. Or rather, I\'m not sure from where came that word. Gotta watch them prepositions, you know.

The swingarm is of course aluminum and it has that groovy banana shape that\'s become synonymous with two-stroke sportbikes. The swing arm\'s movement is controlled by a fully adjustable Ohlins shock with the usual remote reservoir. The RS\'s forks are 41mm Showa upsey-downsey units that are as fully adjustable as the rear shock.

The brakes on the RS 250 are dual, four-piston Brembos up front clamping down on 298mm rotors with a single, twin-piston caliper, out back grabbing hold of a 220mm rotor. The cast aluminum rims are 3.50x17 up front and 4.50x17 out back that require tires of 120/70x17 and 160/55x17, respectively.

The RS gauges feature a digital instrument panel that gives the rider really cool information. There\'s maximum and average speed readings in kilometers or miles per hour, an adjustable rev limiter warning zone indicator, water temperature in your choice of scale, battery charge indicator, a clock in case you have to keep track of when to get home for dinner, and a chronometer that can remember up to 40 lap times.

The Aprilia RS 250 weighs a mere 295lbs dry not counting the spares kit, which includes 2 WP progressive springs for the forks, 2 light alloy front sprockets, 2 rear sprockets of equivalent alloy, 4 Ferodo brake pads, and a rear stand. The RS 250 Cup Challenge motorcycles are also delivered with fiberglass race bodywork.

And no street lighting because the races will all take place during the day. Aprilia tells us that the Cup version of the RS has about 10 more horsepower than the street version though we aren\'t sure exactly from where the extra power comes.

Riding the RS

Aprilia invited the press to try out the RS 250 Cup Challenge bikes at the Las Vegas Speedway in early February. Or was it late January? My, how time flies. Anyway, the Vegas track is easily this country\'s best road course within an oval. It\'s interesting, it\'s varied, it\'s technical and it keeps the riders away from the walls. Well, at least it has the illusion of keeping the riders away from the walls. And there are lots of casinos nearby that sell alcohol in all popular flavors. We had the added benefit of being in town at the same time as the national hair cutters convention. Everywhere we went people had great hair.

At the track we press guys were given a nice presentation about the 4 race Cup Challenge series and then we suited up and went outside to greet the RS 250s waiting for us. There were supposed to be press representatives present from six different magazines but one turned out to be a no-show so traffic was going to be at a minimum. Once the track was reported green, we each set out for a short session to familiarize ourselves with the RS and the track. I had ridden the Vegas circuit last year for the CBR900RR intro but it always takes me a while to refamiliarize myself with a track even if I already know which way to turn at the end of pit lane. Also, it was cold and it was going to take a little time to build heat and trust into the tires.
 

Getting the bike going was the first surprise. I know that two-strokes have little power down low but hey, aren\'t these things actually street bikes? I guess it\'s part of the two-stroke culture to have to rev the piss out of the machine just to get going. I can\'t imagine doing this in city traffic all day long. Maybe it\'s just me.

Yet even as I just started coming up to speed on the RS 250 for the first time, I came to realize why no lazy man ever won a 250 race. On a 250 two-stroke if you\'re "off the pipe", you\'re parked. Ixnay on the orquetay. Not only do two-strokes require learning a track, learning the bike, learning brake markers, turn markers, and acceleration markers, but on a two-stroke you have to learn all of these things to the inch, not just to within a few feet. Everything about riding a two-stroke competitively is about exactness of plan and execution. You can\'t just generally ride a two-stroke well although you can very easily generally ride a two-stroke badly. The best you can hope for is only to try to ride a two-stroke perfectly. That\'s the attempt anyway.

With barely 55 hp, and a power curve so short that it\'s kind of hard to ever really get a good feeling of just exactly how long it is, the rider of one of these bikes has to have a plan. A good plan. This might sound like a pain in the ass but I assure you that it\'s quite the opposite. All racing comes down to which rider can best maximize his bike and his riding to the contingencies of the track but on the RS 250 there\'s much more to doing it well.

On the street I\'m a lazy rider and so there\'s nothing like big-bore torque to make me smile. But racing is a completely different beast than street riding. Racing, at its best, is intense problem solving. Racing well demands a continuous effort of learning, planning, and execution. And more learning. The best tracks are the ones that take the most thought to ride well and it follows that the most fulfilling bikes to race would be the ones that take the most thought to ride well, too. Big, fast superbikes require superlative skills of discretion of rider input but for those of us with too much imagination about the consequences of indiscretion, the fun factor is shadowed under a big cloud called fear. On a racetrack, big bikes take a commitment of the soul. More horsepower means that you\'d have to be braver, but not necessarily smarter.

The more laps I did around the Las Vegas circuit on the RS 250 the stupider I felt. Once I decided to stop riding like the lazy fool that I am, I realized that riding one of these bikes well was going to take more than just one afternoon. Every time I came clean and gave the extra effort to ride the bike properly, I found myself having to work extra hard because of where those new efforts led me.
Committing to extra up-shifts on the bike between a couple of turns caused me to then have to follow through with extra downshifts. Every extra effort that I put into riding the bike properly seemed to create the need for three times the work in order to really profit from the initial commitment. But that is the very joy of racing one of these bikes. It is because it is such a pisser to ride an RS 250 well that it is seductive.

Even riding the bike up onto the Vegas front tri-oval properly was a challenge. While leaned over in the fast sweeper to the front straight, the bike was nearing redline in fifth gear at about 119mph (I knew the speed because the big numbers displayed on the digital speedo are nice and easy to see.). As the bike reaches the banking and it is stood up onto the top of the tires, the revs drop all the way out of the power and the machine just sort of stalls. This catches four-stroke fools like me completely by surprise. The solution is that as the bike is stood up the rider needs to jump back down a gear. Even simply accelerating out of a sweeping turn presents a problem. Work, work, work.

The brakes on the RS Challenge bikes will have steel lines but the bikes we rode still had the rubber hoses in place. This took away from some of the bike\'s potential and gave the brakes an average rather than impressive feel. A hint at the brakes\' real abilities was easily grasped, though. At the end of the back pit straight, when I jabbed the brake lever, the rear wheel jumped from the ground. With steel lines this jump could be a controlled stoppie.

Each bike was fitted with a steering damper and I never bothered turning any more damping into the one I had from the pits to the track. The bike was just plain stable and decisive everywhere on the track.

The RS 250s as we rode them actually were set up with the wrong size rear tires. They were fitted with Pirelli 150s rather than 160s or 170s. I wasn\'t sure if this would really cause a problem or not but after a few sessions I had the rear come around on me while exiting the tight turn back into the infield section from the back straight. Looking at the tires after that experience revealed that the front had almost three-quarters of an inch of unused tread at each side while the rear tire was worn to the edge. On closer inspection of the rear tire we noticed that not only was it worn to the edge but that the outer lip of the tread had been folding over into the sidewall, leaving a small crease just below that lip. There was just no more lean available in these tires. This provided a good excuse to start experimenting with the suspension.

The bike had all been set up for racer Jake Zemke who had ridden one of them here during the season final of the AMA superbike series. Jake is about 4 inches shorter and about 25lbs heavier than I am. The bike I was riding had been set up 40mm of sag in the front and 31mm of sag in the rear. Or so we thought.

To try to get the bike to hook up better in the tight hairpin, John Ethel, the Aprilia mechanic, went three clicks softer with the rear compression. He and I had our doubts about this working but it is the easiest adjustment to make and changing it could then show what really needed to be altered. Just as we had suspected, the bike now was too softly dampened in the fast turns and still too harsh in the tight turns. So I returned to the pits and John took out 2 turns of pre-load which translates to about 4mm of sag. It turned out that the bike I was riding actually had only about 26mm of sag in the rear and so our adding of sag brought the number up to around 30mm. We left the compression where we had moved it to so that I could feel each change we made individually.

Out on the track the bike immediately felt much more planted in the tight turn. I could get on the gas harder, sooner, and concern of the rear coming around disappeared. In the fast sweeper, though, the rear felt gushy and uncertain after about halfway through the turn. I returned to the pits and John put back the three clicks of compression that he had initially removed to stiffen the rear damping back up. This proved to be by far the best compromise.

The point of the suspension tuning was just to see what the changes would do to the bike\'s handling. I needed an excuse to make the changes and if the tires had been of the proper specifications, I might not have been able to find anything to complain about without having to push harder. I am thankful that my job was made a little easier. The result of the experiment showed that the suspension of the RS 250 allowed for changes that were meaningful and easily felt by the rider.

Although the RS is certainly one of the lightest bikes I\'ve ever ridden its handling wasn\'t stunningly better than the latest of the 600s. But I think that that is due to the fact that I just wasn\'t riding the bike hard enough. Since these things are about 100lbs lighter than modern 600s it takes more effort from the rider to work the suspension as hard as a 600\'s. Since my butt is tuned to judge overload on the heavier four-strokes I was clearly being a wimp on the RS. What is also clear is that this bike is tons of fun because it is a lightweight two-stroke regardless of my prejudice of what\'s under the fairing.
 




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