Suzuki Rm250t
SUZUKI RM250T
CYCLE WORLD TEST
Not Much Changed,But Still Comnpetitive
Almost every part of Suzuki’s 1979 RM250N was new. The bike proved raceworthy out of the crate and many local
pro riders won with
virtually stock motorcycles. Most racers didn’t change things, even the shocks—which are excellent—until the parts wore out. Even with this enviable record, motocross progress is measured in weeks and most expectations were that the 1980 RM250 would be as changed as the ’79 RM250 was.
Nope. The RM was a winner last year, R&D has had lots of other work to do (as in the PE, DR and GS lines) so Suzuki figured the 250 could be given some minor polishes and be competitive for another season.
The ’80 version is labelled “T”, another big jump in the numbers series. Originally the RMs came as A, then B, then C, and then N, we were told because the radical changes made the bikes—get it?—New. So what does T stand for? Nobody will say, but then again, they couldn’t call the new race bike an “O”, could they?
The most obvious change on the 250T is the chain guide. It's a large unit that guides the #520 chain onto the aluminum rear sprocket while wiping mud off the sides of the sprocket. Last year’s spring-loaded tensioner has been replaced by a stationary roller under the swing arm and a plastic rubbing block that protects the arm’s top and bottom.
Another small but equally important improvement are the rear sprocket bolts. The old ones, with recessed heads, in the past have caused broken hubs. The new bolts have thicker heads and the alien wrench head size has been increased from 5 to 6mm. A washer is also used between the self locking nut and hub. Past problems occurred when the bolts weren't tightened enough or the shouldered bolt stretched and the nut bottomed against the shoulder, giving a false impression of being tight. Either condition soon caused a broken hub. The hub has also been strengthened by adding two more webs. The changes should stop the hub and sprocket problems of past models. We raced ours several times and the sprocket never loosened.
A non-RM owner may not notice a difference in the KYB reservoir shocks, but they have been significantly improved. Rebound damping adjustments have doubled. from two on the N to four for the T. Three spring preload positions remain, but the shock’s most notable improvement is the addition of an air valve mounted on the reservoir. The valve allows oil and pressure changes. Unfortunately they can’t be completely rebuilt because the top of the shock body isn’t removable. KYB shocks have a reputation of lasting a long time and seals don’t start leaking often, but when they do. they will have to be scrapped.
The RM’s rear brake linkage has changed from a rod to an exposed cable.
The exposed cable has eliminated the chatter sometimes experienced when braking hard with the N. Another small but important addition is a return spring for the rear brake arm. Past RMs have suffered from brakes that stuck partly on when used in mud or extremely dusty conditions. The new spring fits between the brake arm and backing plate, forcing the arm to the return position under the most severe conditions. Unfortunately, the large full width front brake doesn't have a similar spring. We have added return springs to the front brake arm on staff owned RMs for years. The front brake lever on our test bike started sticking the first ride. We disassembled the unit and greased the brake cam, which helped, but even then the brake had a sluggish return.
A less obvious change is the CDI advance curve. It has been changed to give better torque and horsepower. And the T has plenty of both. It has about the same power as Yamaha’s 250G but better low end torque. It pulls from low revs with no explosiveness or bad manners. The transmission has five gears, with ratios perfectly matched to the engine’s power and final gearing is right for most motocross tracks. The CDI is about the only new part on the T’s engine. Cylinder porting, case feed reed valve induction, crank, rod, piston, 36mm Mikuni carb and cases are the same. These parts were mostly new last year and performed fine so a change wasn’t needed.
Plastic parts on the T are both new and old: the fenders are a new smooth wide shape styled after the Suzuki works machines. The number plates and tank are the same pleasant shape the N used. The tank holds 2.2 gal. of premix, has a good plastic cap and a reasonable sized filler hole.
The seat is another item that hasn’t changed. It has a nice shape and looks thick enough, but long motos prove appearance wrong. Like Suzuki RM seats of the past, the foam is the wrong density and a sore butt results from extended riding sessions.
Most controls are properly placed and shaped on the T. The handlebars are the right width and bend, the hand levers are easy to reach, the rear brake pedal and shift lever are the proper length and placement and have rough ends to prevent boot slippage. That leaves the throttle and kick lever; both poor designs that Suzuki continues to use year after year. The throttle works all right, but it is too short. Large hands don’t fit and aftermarket grips have to be trimmed. The kick starter is another matter. It has a nice rubber cover to keep mud out of the pivot, folds completely out of the way, but misses the boat with its slippery non-ribbed end. Kick starting an RM with muddy or wet boots can be torture. Every time the engine fires the kicker’s boot can slip off and the lever usually digs into the calf of the operator’s leg. Even dual purpose bikes furnish ribbed kick levers.
It seems strange that Suzuki can have the worst kick starter, and the best footpegs^ on the same machine. And the RM pegs are the best. They have' many small teeth that grip the boot soles without cutting them and strong return springs. They never stick up when the bike is used in mud.
All of the ’79 RMs had new forks and they are unchanged for ’80. Stanchion tube< diameter is 38mm, travel is 11.2 in. and they are air adjustable. Triple clamps are aluminum and the top clamp has rubber mounted handlebar mounts to cancel shock and vibration. Good gaiters are furnished and the fork seals don’t leak or have excessive drag. «
The frame, another part totally changed last year, remains the same. It is constructed from chrome-moly steel and its shape is similar to the Suzuki works motocrossers. The single downtube design places the swing arm pivot close to the rear-set countershaft sprocket and4 provides good triangulation under the tank and seat.
An extruded aluminum swing arm. also new last year, is lightweight and neat looking. It pivots on needle bearings and has wheel adjusters that stay in place when the axle is removed. Suzuki has one of the best rear wheel adjusting systems around. Adjusting the wheel doesn’t require loosening the axle, just the two large nuts closest to the arm. And axle removal doesn't disturb the chain adjustment or create an avalanche of falling parts.
We raced the RM at several local events. It proved competitive in spite of being little changed from last year. Horsepower is good and the racer won’t be outrun to the* first corner if the other racers are using stock engines. Transmission gear ratios and final gearing are good and matched well to the engine’s torque curve. Shifting is positive and smooth, and restarting a stalled engine is simple, due to the primary kick starting. Suspension is well balanced and works fine on a variety of terrain; it is supple over chatter bumps, and doesn’t bottom hard in deep gulleys. The bike stays straight overjumps and lands softly without excessively jarring the rider. Both brakes are strong and progressive and don’t chatter when used hard in downhill whoops.
The T is a reluctant turner without a berm. It goes through a bermed corner like it was on rails but skates the front tire without one. We dropped the front of the bike by pulling the fork tubes up through the triple clamps a half inch, improving the cornering considerably. Although better, the RM still takes second seat to a Maico or Yamaha YZ-G in a flat corner. Forget about sitting on the seat through a slippery off camber corner, the top of the tank is the position required to get the RM through ^such a corner quickly, otherwise the front tire will skate. We changed the front tire to a 3.00-21 Hi-Point and reduced the skating some but a far forward, half seat.-half tank position was still required for quick turns. The RM simply doesn’t turn as well as some of its competition, but a full time racer can adapt and set some impressive lap times on most tracks anyway.
SUZUKI
RM25OT
$1819
The new RM250T won’t dazzle many with its few really new components for 1980 but it is still competitive and worth the asking price.
