Trials Competition Newspaper - Feb 2005
Test: 2005 Scorpa SY-175F
Good Things Come In Small Packages
The Foundation
In 2004, while pundits tagged the then new Scorpa 125cc 4-stroke as “just a trail bike engine stuck in a trials bike frame”, Loris Gubian was busy winning the European 125 Championship and proving the new Scorpa’s capability as a “real” trials bike. Designed to fulfill the 125cc limitation in certain classes, and the pending mandate for 4-stroke engines, the bike had an intended purpose and was successful in achieving it. Even so, the factory and others obviously considered early on that a larger displacement version might be appealing to an even larger audience. When Scorpa’s 4-stroke prototypes first appeared at the SSDT, there were two bikes with the 125cc engine, and two other examples sporting a larger 143cc displacement. And, when the very first production SY-125F 4-stroke hit U.S. shores last year, it went straight to B&J Racing, in Tennessee, for the development of various performance modifications, which included a 143cc kit. From the beginning, “larger” appeared as if it were a given.
Factory Hop-Up
With strong sales in 2004, the TYS-125F (LongRide) and SY-125F (Racing) have proven to be popular new additions to the Scorpa lineup. Building on this success, ongoing development of the Racing model resulted in new prototypes being shown during the year, including a higher performance 125, a bored 143cc version, and a bored and stroked 170cc version.
Among the results of this R&D effort are the many performance components (bore kit, stroked crank, cam, CDI ignition, carb, intake, exhaust, etc.) now offered in Scorpa’s new 2005 Performance Parts Catalog. But, the premier result has to be the new 4-stroke SY-175F racing model, which features a production version of the 143cc engine, select items from the new performance catalog, and the same top-shelf billet CNC components, Paioli forks, SACH’s rear shock, AJP calipers, BRAKING rotors, 32 spoke wheels, hubs, etc. found on the SY-250 2-stroke.
Impressions
We were pleased to accept when Mike Komer, of the Tryals Shop, (U.S. and South American Importer for Scorpa) offered us a SY-175F for a long-term test. Having now spent 10 to 12 hours ride time on the bike, we have had an excellent opportunity to experience the new Scorpa under a variety of conditions.
Straight out of the box, the bike strikes you with the compact packaging of the 4-stroke engine, which is further emphasized by the absence of an exhaust mid-chamber, cooling hoses, fan, or radiator. Its 164 pound weight is within one pound of the SY-250, yet gives the impression of being much lighter. This feeling continues when riding the bike, as it is narrow across the engine cases with an exhaust header roughly half the diameter of the typical 2-stroke pipe. The sensation that the bike is very light and nimble is an immediate impression that was shared by each of our test riders, with one commenting that, “It feels like I’m riding a bicycle.”
Prior to riding the bike, it would be natural to presume that the 143cc 4-stroke engine will be underpowered. Upon riding the bike, that presumption is quickly dispelled. While the bike does have “less” power than a typical 250cc 2-stroke, each of our test riders agreed that “underpowered” was not an appropriate description. The power is softer, and requires a more aggressive throttle hand on the larger stuff, but will motor right on up in its own unique way.
With the current prevalence of 2-strokes, there are a number of things about the bike that feel unique, such as the 4-stroke power delivery, torque curve, and compression braking. These characteristics manifest themselves through the very real feeling that the rear wheel is more consistently connected to the ground and better able to hold traction. It is interesting to note that this trait seems to be further enhanced by the smaller displacement engine. The softer power results in the ability to be more aggressive with changes to the throttle, without producing wheel spin. On an off camber surface, such as a turn across the face of a hillside, the result is less dabs due to the rear wheel spinning and kicking out from under the rider. There are a number of engine characteristics, such as this, that are a definite advantage and demand to be weighed against any disadvantages, real or perceived.
As we expect will be the case with all the new 4-strokes, getting the most out of the new Scorpa will require a change in riding style. For example, much like a vintage bike with a heavy flywheel, the 4-stroke works better in most cases when you simply leave the clutch alone. The engine is content to pull smoothly down low and allow you to motor through the section just using throttle and brake control. This is also true when turning the bike downhill. Rather than pull in the clutch and use rear brake modulation skills to try and control wheel lockup and slide, you simply leave the clutch out and let the engines braking compression work for you. While testing, one of our practice sections had a leaf and pine needle covered downhill. On a 2-stroke, our test riders would inevitably have some degree of rear wheel lockup and slide, while the Scorpa 4-stroke would almost naturally maintain traction and control during the descent.
Considerations
When we first unpacked and ran the SY-175F, our initial session was shadowed by an inconsistent idle and a tendency for the bike to easily die without warning at low RPM, such as in a tight turn. We chalked it up to a new engine and clutch that needed break-in time. After a few break-in hours, there was some improvement, but not enough. The diagnosis was lean jetting starving the engine of fuel. On advice from B&J Racing (www.bjracing.com) we changed from a 15.0 to a 17.5 pilot jet. The results were impressive as warm-up time decreased, a smooth consistent idle was achieved, and the engine now runs clean down to very low RPM. While at it, we also performed their recommended modification to the silencer core by removing the four restrictor rods. There was a VERY minimal increase in exhaust noise, yet a mellow bark and improved bottom-end were realized.
Another of B&J Racing’s various performance enhancements for last years SY-125F involved the clutch. By modifying the steel plates for greater oil flow, using friction plates with a different fiber composition, a different cable, and a clutch lever with greater mechanical advantage, the competition capability of the clutch was improved. For the new SY-175F, the Scorpa factory has replaced the manual pull lever and cable with a Magura hydraulic unit that results in 20% less lever pull. An added bonus of the Magura setup is the handlebar mounted choke lever, which makes the cold starting procedure easier than ever and a gloves on proposition.
While the new Magura hydraulic unit signals the factory’s desire to improve the new racing model’s competition performance, we have not yet confirmed whether any changes have been made to the steel plates or friction plate material on the SY-175F. The clutch does continue to improve with break-in time, but we have so far found the feedback to be somewhat vague with a range of engagement more narrow than we would prefer. As a solution, rather than locate the clutch perch at a point where the index finger naturally falls near the tip of the lever, we instead located the perch further out toward the end of the handlebar, where the index finger falls closer to the levers pivot point. Most of our test riders felt that this provided better feedback and control over the clutch’s range of engagement. As stated earlier, the SY-175F often benefits from relying on the engines low end torque, rather than the constant use and modulation of the clutch anyway. Still, in very tight technical sections, clutch modulation is a necessity and a wider range of progression would be a plus. If we learn that the factory has not implemented a new design for the steel plates and friction plate material on the 175, curiosity may result in our trying the B&J Racing clutch modifications. If so, look for more details in a future issue.
Conclusion
For 2005, Scorpa continues with the division of its model lineup into the “LongRide” and “Racing” families, with the Racing models featuring the higher end components intended for competition. As a member of the Racing lineup, the SY-175F is no exception. Overall, we find the package to be well designed with an excellent build quality. With no premix, racing fuel, radiator, fan, thermostat, coolant, coolant pump or hoses, there is no denying the rugged simplicity of the air-cooled Yamaha 4-stroke engine, long proven bulletproof in the TTR trailbike. But, to dismiss the newest 4-stroke Scorpa as a trailbike in disguise, or just a beginner’s trials bike, would be an unfortunate mistake.
Specifications: 2005 Scorpa SY-175F
Engine Type: Air-cooled 4-stroke SOHC
Capacity: 143cc
Bore x Stroke: 58 x 54 mm.
Spark Plug: NGK CR4HSA
Ignition: Boitier CDI Racing
Fuel: Unleaded
Carburetor: Mikuni VM20SS
Transmission: 5 speed
Oil: 1 Liter Motul 300V 100% Synthetic
Final Drive: Chain (14 x 57)
Brakes: Disc (Front/Rear)
Suspension:
Front: Paioli/Scorpa Racing 36mm
Rear: SACHS Linkageless