Special Forces

SPECIAL FORCES

A crack team of performance commandos infiltrates the 250 MX class

WE'LL ADMIT IT. WE'RE greedy. There's an inescapable principle governing interactions between human beings and motorcycles. The more we get, the more we want. So the better a motorcycle is, the better it has to be. You want examples? Take a look at the motocross world. No matter how light, fast, smooth or trick the new models are, we, being only human, want them to be lighter. faster, smoother and tricker.

That's why we've regathered the 1990 250 motocrossers here. Last February, Cycle World came to the conclusion that this was the most awesome group of production moto crossers ever made. The Honda CR25OR had an unstoppable motor, Kawasaki's KX250 had excellent suspension, the Suzuki RM250 could outcorner a jackrabbit, the Yamaha YZ250 was a masterpiece of line holding stability.

But till, our~want-glands were se creting way too much greed into our bloodstreams, and as awesome as the 250s were, we wanted them to be bet ter. So we took each of them to a dif ferent aftermarket firm, and trying to hide the slight glint of saliva drooling from the corners of our mouths, we reported that we wanted more. Much to our surprise, we got just that.

c' J And this time around, we threw in a wild card. Although scheduling problems prevented us from includ ing a modified KTM250 (we'll have a report in a future issue), we did get a hold of another non-Japanese 250 motocrosser, though, the Husqvarna WMX250. The Husky arrived too late to make it into our February shootout, but we did put some time on it afterward. We discovered rather quickly that its suspension didn’t work very well, even compared to the worst of the stockers, so we decided to have Z Racing perform some of its magic on the White Power fork and shock. Mark Zoller is the firm’s suspension specialist and he concentrates on personalizing suspension to an individual's needs. In the case of the Husqvarna. he increased the spring rate in the fork and did some serious revalving at both ends. The cost for the fork was $170, and the shock modification was $ 130.

The Honda got very similar treatment. It was the top bike in our original comparison, and our only complaint at the time was that its suspension wasn't up to par with the rest of the machine. So suspension sorcerer Bill Rychlik at White Bros. Cycle Specialties was put on the case. He revalved the fork and replaced the springs with AMP Research fork springs (White Bros, has since switched to Noleen springs), for a retail cost of approximately $230, including parts. The price can vary depending on the condition of the fork when it falls into Rychlik’s hands. The rear shock was revalved as well, but Rychlik elected to leave the stock spring in place, which kept the price for the rear end down to about $ 150.

Like the Honda, we had only one serious complaint with the Kawasaki, but it had nothing to do with the suspension. The KX’s power delivery was too abrupt, making the bike hard to handle. Bill Keefe at Klemm Research stepped up to that challenge. He ported the cylinder and machined the head to his “National” specs, with slight deviations to make the bike mellower, as per our request. The head’s squish band was reshaped, the bottom of the cylinder was shaved and all the ports were altered. Cost: $245. Keefe also blueprinted the motor (its crank was trued, gasket surfaces lapped, cases pressure tested, etc.) for $285. For another $55, he modified the shift mechanism so the bike would shift easier, and for $94.50, he bolted a Klemm carbon-fiber silencer onto the stock pipe.

Unlike Rychlik and Zoller, who do only suspension, and Keefe, who does only engines, Rusty Hadley and crew at Suzuki Country Racing do both. So when we gave them the RM250, they went a wee bit overboard with modifications. First of all, their “Stage 5” porting was done ($169.95), then they, too, reshaped the head ($85). They bolted on the SCR Pro Pipe ($ 159.95) and the SCR reeds ($24.95), and then they installed a bored and heavily modified Keihin carburetor ($264.95). SCR went on to do suspension work, even though we rated the stock RM quite highly in that department. They felt they could do better, so both ends were revalved for $ 149 each.

Then they started bolting on some of their accessory parts, none of which made the bike any faster, but all of which made it a lot tricker. These ranged from an assortment of carbon-fiber parts (silencer, disc guards, chain guide) to SCR’s machined T-6 aluminum triple clamps. The result was a very flashy package, and an expensive one, too. The SCR RM received a total of $2450 worth of modifications and accessories.

As for the Yamaha, it got the complete treatment from Paul Thede’s Race Tech. Thede has long had a reputation as a man who does some of the best suspension work in the industry, but recently, a great deal of his business has involved engine work, as well. For revalving the fork, he charged $120, and for the rear shock, it was $175. If the rider’s weight or riding level calls for a heavier spring rate, Thede will modify the stock units for $40 each. He also did $200 worth of modification to the ports and the powervalve, and he modified the head’s squish band for $70. Weight was added to the bike’s stock flywheel ($90) and then he bolted on a $120 Race Tech shifter, which many riders consider the only real cure for the YZ’s notoriously notchy shifting.

So what happens when you take the world's best motocrossers and make them better? Your standards change, that’s what. Suddenly, flaws that were invisible before are all too apparent. Human nature is human nature, so once old complaints were cured, we simply invented new ones.

For example, the Z Racing Husqvarna was worlds better than the stock version. The suspension seemed to appeal most to Intermediate-level riders, whereas before the modifications, no one could tolerate it. But without the suspension woes clouding our vision, we were able to see a multitude of other problems, such as erratic power delivery and an awkward riding position. Had the stock Husqvarna been in our original comparison, it would not have done well. And, had the modified Husqvarna been in that test, it, too, would have finished in last place, although by a lesser margin.

We didn’t give the Honda much more work than the Husky, but the finished product was much more palatable. Making an already-excellent product even better is a tough job, but the people at White Bros, came through. The modified CR was impressive, as our Proand Intermediate-level riders could come up with nothing to complain about, suspension-wise. But not so in the power department. By comparison with the 250s that had undergone engine modification, the Honda seemed a touch too mild. Sure, it was fine back when it was running with the Stockers, but suddenly the CR was keeping more serious company. Its powerband still was smooth and easy-going, but just a pinch more horsepower would have helped out tremendously against the others. Amazing how quickly standards can change.

We ran into a similar situation with the KX. With the engine’s flaws occupying all of our attention, we didn’t think its suspension was a problem. But in this reworked, revalved field, the stock KX suspension simply wasn’t up to the task. Klemm Research’s motor modifications, though, did a remarkable job of smoothing out the KX’s powerband. The bike no longer had a raspy, sputtering low-end leading to a harsh mid-range. Instead, it was the smoothest motor of the bunch. The machine almost felt like an enduro bike, with a powerband so smooth and flat that you almost could go bowling on it. Perhaps it was too smooth. More experienced riders will want some extra punch, so it’s easier to lift the front wheel over obstacles. Most of our riders found that the bike’s peak horsepower was disappointing. We accept part of the blame; after all, we did ask Keefe to mellow out the bike’s manners. On a positive note, the vibration that we complained about in the original test was all but eliminated when Keefe rebalanced the crank.

The Race Tech Yamaha was much better received, especially in the suspension department. Most riders initially felt that both the fork and shock were too soft, but in almost every case, they changed their minds after spending some time on the machine. The bike worked surprisingly well on all the little stuff, and never asked for any kind of toll in exchange. It absorbed big impacts without bottoming or doing anything nasty, making fans among all levels of riders.

In the case of the YZ’s power, the stock engine was perhaps the farthest off the mark, mostly because it ran out of beans too early. After Thede had worked the powerband over, though, the YZ had a motor that was more impressive than either the stock Honda or the Klemm Kawasaki. It was delightfully smooth, with power coming on much earlier and lasting much longer than before. It still was a short-shifter, without much of a kick on top. But the lowand mid-range power was so much fun that it didn’t matter. The Race Tech YZ gets the award for most-improved 250.

But when it came to sheer horsepower, the winner of the group was the SCR Suzuki. The meat of its powerband didn’t necessarily start at lower rpm than the Stocker’s, and it didn’t necessarily rev any higher. But, brother, what it did in between. The SCR RM jumped into its powerband sharply, pulled through a positively rabid mid-range, then left you wondering if you were ready to upshift and do it all over again. Its powerband was pretty much the same as the stock RM’s, it just made more. Lots more. On a technical track, the SCR RM could be a bit of a handful, demanding a skilled right wrist, but when the venue was wide open, the Suzuki was the bike.

In the suspension department, too, the SCR bike catered to a Pro-rider mentality. The faster the rider went, the more the bike liked it. Both ends were a touch stiff, but otherwise worked quite well. It was a bike that could intimidate beginners and even some more experienced riders. But that wasn’t enough to keep the Suzuki from being our favorite bike of the bunch. Its horsepower was just too good not to like. Of course, the Suzuki had the most money thrown at it, and that showed.

We’ll chalk that up as a lesson well taken. There are some things that money can’t buy, but MX-bike performance isn't one of them—you really do get what you pay for. What else did we learn? Plenty. First of all, we confirmed our suspicions that humans, being only human, can never be satisfied. Despite how good these bikes were in the first place, we had enough gall to want them to be better. And perhaps most important, we learned that we shouldn't ever be satisfied. Because no matter how much you get, when it comes to race-winning technology, you can always have more. 0

SUPPLIERS

Z Racing

2350 E. Orangethorpe Anaheim, CA 92806 714/449-1271

White Bros. Cycle Specialties 14241 Commerce Dr.

Garden Grove, CA 92643 714/554-9442

Klemm Research 139 N. Maple, Suite G Corona, CA 91720 714/272-8480

Suzuki Country Racing 2057 N. Hammer Ave.

Norco, CA 91760 714/734-0640

Race Tech

3227 Producer #127 Pomona, CA 91768 714/594-7755