Ossa Pioneer 250

OSSA PIONEER 250

A Lightweight, Slim and Nimble, Good Just About Anywhere, But Happiest In The Boondocks.

SO WHAT’S SO BAD with duding up a workhorse? You’ve seen those big, hairy-hocked Clydesdale horses with feathers and plumes on them. Nothing fruity about that. And they pull those big beer wagons around rather well. So just because the Pioneer has some style, don’t think it hasn’t got what it takes. The engine’s a little bigger now, and stronger. It’s one of the ruggedest bikes made. A CW staff member was so impressed with the test bike, he bought an identical Ossa of his own.

Resplendent in orange and black high impact fiberglass, the Pioneer looks more like a one-off custom than a thoroughbred enduro bike. Glasswork is neat and smooth, devoid of rough spots or irregularities. Paintwork is similarly professional with a tough chip-resisting finish. While chrome is scarce on the Ossa, polished aluminum abounds, including the wheels, hubs and engine cases.

Ossa suspension is excellent. The front fork is from Telesco and provides consistent, predictable damping throughout its 7-in. travel. To ensure long life, bearing insert material in the slider legs is not bronze but babbit metal, which will embed foreign matter creeping in past the seal. The rear spring/ dampers allow 3.75 in. travel and are five-way adjustable.

The Ossa frame is conventional and strong, in keeping with the bike’s tenor. It is a duplex configuration with a large diameter backbone and made of seamless steel tubing. The stoutly gusseted steering head accommodates the fork stem with a pair of Timken tapered roller bearings, while at the other end, rubber bushings support the oval section swinging arm. In spite of some dreadful pounding, the frame refused to flex. The frame is the same as that of the Stiletto scrambler and the geometry is also identical. The Pioneer shows a slight reluctance to steer away from a straight line, and the steering is desirably slow. This actually is beneficial during high speed stints over rough terrain, as it enhances stability. CW testers Banzaied the bike at 40 mph over a series of one-foot high hoop-de-hoos with nary an errant waggle. Its light 242-lb. curb weight makes the Pioneer extremely nimble in tight going.

The seat is of ample width, but the frame and fiberglass work amidships is trim enough to allow a comfortable standing position with snug knee grip and feet secure on the pegs. Handlebar position and width allow good rider posture and good weight distribution.

The Ossa’s muffling system is quite effective. It silences the bike very well for street riding, even though it doesn’t look so sharp hung out there at the end of the expansion chamber. But for off-road riding, the small chrome, bulbous muffler can be removed in a matter of seconds. When not in use, the unit is carried on the back of the expansion chamber on the bike’s left side, and there it is held by a retaining spring. This is particularly convenient, as the machine is equipped with all the other state prescribed accoutrements, so you can use public roads en route to the boonies, fearless of the sheriffs scathe.

In the electrical system, a solid state regulator controls battery charging from the alternator coils. This should provide rehable performance for some time to come. The electronic ignition, though highly mysterious to many, is another Ossa plus. This system has been on these machines for a couple of years now with a great deal of success. But then, this arrangement is actually simpler than the more conventional battery-coil or energy transfer systems and inherently more reliable.

In the Ossa’s Motoplat ignition, current is generated as flywheel magnets sweep past pickup coils. This current is stored in a condenser. As the flywheel continues rotating, another magnet spins past the coil that “opens the valve,” releasing the stored-up current into the high tension coil, and consequently, the spark plug.

As moving parts within the system are minimal, and breaker points are eliminated completely, its advantages become apparent. Problems of point wear, bounce and adjustment no longer exist, and the system’s voltage rise occurs in microseconds (millionths of a second) rather than milliseconds (thousandths). Because the current build-up is so much quicker, usable plug life is three to five times greater than that of other systems. Instead of a portion of the current leaking away prior to plug sparking, as in non-transistorized units, the Motoplat delivers such a quick jolt that there isn’t time for electrical dissipation. It will fire a plug that’s literally dripping with oil.

The Pioneer’s engine is much the same as its 230-cc precursor, the main differences being a 2-mm increase in bore (now 72 mm) and a drop in compression ratio from 11.4:1 to 10:1. It seems that the factory has opted to detune the engine slightly along with its displacement increase, maximizing long-term reliability.

The crankshaft assembly rotates in ball bearings, while the connecting rod has roller bearings at the big end and needles at the wrist pin. The three-piece crankshaft is pressed together at 15 tons pressure to ensure alignment under prolonged stress. The tapered piston is cam ground to provide for almost exact conformance to clearances within the iron cylinder liner at operating temperatures. On the crankshaft’s primary side there is a hefty, spring-loaded cush-drive to absorb any shock impulses transmitted by the duplex primary chain. The four-driven, four-driving plate clutch performed flawlessly, with no hint of slippage, overheating or related vices.

In the gearbox, each shaft is individually shimmed to the specified tolerance. The mainshaft is supported by a doublerow needle bearing at the clutch end and a ball bearing at the opposing end.

Due to these closely followed clearances, the transmission was at first a bit tight, resulting in an occasional missed shift. Things loosened up in a short while, however, but patience may be required of the new Ossa owner.

Another dash of sophistication is the double needle IRZ carburetor. In this unit, there are actually two venturis and metering systems. A horizontal divider in the carburetor bore separates the two systems. In the slide, there are two needles, the low-speed one in front, looking from the intake side. At smaller throttle openings, the slightly raised position of the slide leaves only the low-speed system in the airstream, the high-speed system being isolated by the divider. When the slide is tugged higher, the other metering nozzle is exposed, bringing it into play. Simple and neat, the carburetor allows clean and smooth throttle response under all conditions, but particularly at low engine speeds. One would expect a surge or flat spot at the transition point between the two metering systems. Not at all. Carburetor response is totally consistent. An unexpected benefit of this design is the Pioneer’s modest fuel consumption, a definite advantage for an enduro bike.

The cylinder head is tapped to receive a compression release if so desired. Among many motocross riders, the things aren’t so popular except to aid starting larger two-strokes. But for enduros and trailing, they can be quite valuable. When attempting a precarious descent with marginal traction, for example, you can steady yourself with both feet on the ground, and brake with the release. But the Ossa, like any other bike, can be damaged by indiscreet use of these gadgets. When the lever is pulled, the engine inhales a lot of air, usually unfiltered, and often to the point of disrupting lubrication.

The Pioneer’s brakes, identical to those on the street-going Wildfire and the hot Stiletto scrambler, measure 6.2 in. in diameter and 1.6 in. wide. With such comparatively large brakes on such a light machine, you’d think the wheels would lock at the slightest application. Not so. Although steep hills require a certain amount of caution, the brakes seemed not the least pugnacious in the dirt. Nor did the cable-operated rear brake tend to chatter or grab. Throughout the test both brakes proved strong and smooth.

There is one minus point, however, and we wouldn’t even mention it if the bike were touted as a scrambler rather than an enduro machine. There is no trip reset knob on the odometer. These buggers are a necessity for enduro events, as they allow the rider to more accurately compute checkpointto-checkpoint progress.

Thanks to conservative port timing and strong ignition, the Ossa never needed more than a couple of easy kicks to get started. Warming up, there is little audible piston slap, indicating a snug piston fit. The primary chain is also very quiet, a pleasant change from the whir and thresh we’ve come to expect.

Because of its generous torque at low revs, the Ossa will pull away cleanly at idling speed in low. The width of its power band is excellent. During the test, one staffer found himself at a dead stop halfway up a steep, powdery hill. Instead of curling up in the fetal position, which might be appropriate in such frustrating circumstances, he quickly restarted the torquey lightweight, toed it into low, and with a wisp of wheelspin, continued to the top. Truly, in such a predicament as that, only a machine of the Ossa’s excellence could have dispatched the challenge.

The Ossa makes little pretense of being extremely fast, extremely robust or extremely anything, yet we are left with a particularly strong impression: mechanically, nothing is highly stressed in this bike. Strength and reliability have received the most emphasis in its design and few other machines, regardless of price or purpose, have achieved design objectives so completely. [o]

OSSA

PIONEER 250

$785