Suzuki Rm125t
SUZUKI RM125T
A New Rear Hub and Adjustable Shocks Make the '80T a Better Bike Than the '79N
CYCLE WORLD TEST
Suzuki's RM125 has seen more than its share of winner circles. Last year (1979) like the rest of the RM line, the 125 received major design and styling changes. Mechanically the '79 RMN was very good. but the Star Wars styling met with mixed reaction. Most people thought the strange fender shapes would be better in a science fiction movie.
For 1980 the RM125T has the look of the Suzuki works machines. The fender shape is more rounded and simple. Tank decals and seat logo are also new but only an owner of a 1979 Suzuki RM 125 would notice the difference.
Mechanical changes are minor. Most were aimed at polishing the rough edges and improving an already good package.
The 428 final drive chain has finally been discarded. In its place is a beefy 520. Final drive sprocket sizes have been shuffled around—the '19 used a 12/51 combination, the ’80 uses a 14/59. Final ratio stays almost the same but the larger front sprocket means the chain doesn’t have to make as tight a turn, which means longer wear.
The spring-loaded chain tensioner from last year has been scrapped. A stationary roller just below the swing arm pivot takes its place and does away with the troublesome spring. The small plastic roller mounted on top of the swing arm has also been eliminated. In its place a flat plastic skid pad keeps the chain off the beautiful extruded aluminum swing arm and doesn’t need constant replacement.
A works look-alike chain guide is solidly mounted just in front of the rear sprocket. It extends past the point of chain contact with the sprocket and contains plastic rub blocks that clean the mud from the sides of the sprocket. These changes and a countershaft sprocket centered 2.7 in. from the swing arm pivot means an end to chain problems on the smaller RMs.
Another subtle but worthwhile change is the rear brake linkage. The brake rod has been changed from a rod to an exposed cable. The exposed cable is large enough to provide the feel a rod has but makes linkage geometry less critical. This minor change has eliminated the chatter and rear brake lockup the N sometimes experienced on rough down hills. Another contribution to the excellent downhill braking is the addition of heim joints at both ends of the torque arm. The importance of the torque or static arm is often disregarded. When the torque arm is part of a fullfloating brake system like the RMs. smoothness of operation is critical; if binding or seizure occurs, the rear suspension will lock and become useless.
The best change on the 1980 model is a new rear hub. Outwardly it looks like the same explosive part, but isn’t. Rear hubs have been a real problem for past RM and PE owners. If the rear sprocket came loose, even once, a broken rear hub would follow. Problem was, the sprocket on some machines was almost impossible to keep tight. The new hub has the same outward appearance but close inspection shows two additional webs have been added to the area between the sprocket flange and the hub’s center. The new design puts a web at each sprocket bolt flange. This simple change has eliminated the problem of loose sprocket bolts and broken hubs.
Suspension on the new T is a combination of old and new. Forks are unchanged from '19. They have 11.2 in. of travel and their 38mm stanchion tubes give excellent feedback. Damping and spring rates are right on and the forks are fully tunable by altering fork oil volume, oil weight and air pressure. Visually the triple clamps are the same. Internally, the steering stem is larger for increased strength. And like before, they pivot in tapered bearings.
Every year the Suzuki KYB shocks get better. They worked well last year but didn't offer much in the way of adjustability. The T model has shocks that allow three spring preload adjustments and four damping adjustments, ranging from soft to stiff. Additionally, the reservoirs have been fitted with air valves to adjust the nitrogen pressure. They come set> at 228 psi per side and can be set as low as 142 psi or as high as 284 psi. The addition of the air valve also makes oil changing possible. The procedure is lengthy but it’s explained well in the owners manual. Unfortunately, the shocks can’t be rebuilt. Maybe next year.
Refinement is the name of the game for the engine. Bore and stroke are still 54 x 54 mm, carburetion is still via a 32mm Mikuni and six-petal reed valve and transmission ratios are exactly the same. Cylinder compression ratio has been raised slightly to 8.1:1 from 8.0:1. The significant changes to the engine are a heavier crankshaft and new ignition timing. Timing has been advanced from 12° BTDC to 16° BTDC. both at 10,000 rpm. The heavier crank, advanced timing, and a fatter expansion chamber combine to produce a wider, more useful powerband. The engine power and transmission ratios are now perfectly matched. Keeping the 125 on the pipe is easy for any racer. Shifting is smooth and positive but full throttle, no clutch shifts aren’t possible—the clutch will have to be pulled or the throttle shut before the shift lever will move. Fast shifts can be completed with practice but the Kawasaki KX gearbox shifts much better.
The RM 125 T uses the same frame as the N except for some additional gusseting around the steering head. It is a single downtube design with a large backbone. Triangulation under the seat area is excellent and flexing won’t be a problem.
Footpegs are some of the best ever put on a motocross machine. They are heavy duty cast items that provide a good sawtooth top edge and extra strong return springs.
Complaints? Yes, we have a couple that Suzuki continually ignores. First is the killer kick start lever. Last year Suzuki cured the problem with the lever coming loose and falling off, but left the slippery non-ribbed pedal the same. Starting an RM with muddy smooth-soled motocross boots can be painful. It’s almost impossible to kick one over without slipping off at least once. And the end of the pedal almost always tries to impale the starter’s leg after his foot has slipped off it.
Next on the dislike list is the threequarter sized throttle. It works well but isn’t long enough for large hands and accessory grips have to be shortened before they will fit.
The foam filter is large but does a poor job. It lets dust through even when heavily oiled and greased. Replacing it with a good one should be considered mandatory. For some reason Suzuki has replaced the pull pin filter retainer with a wing-nut screw and it is a genuine pain to align.
The pipe burns the leg of the rider in tight lefthand corners and the silencer isn’t repackable.
The front brake cable clamp won’t do its job when a hard rider is aboard. It lets the cable housing slip down when the forks are bottomed. When the cable slips it transmits a funny feeling to the rider through the brake lever. Kawasaki uses two clamps for the cable and they do the job right.
Tires are IRCs and worked poorly under most conditions. The front is the worse of the two, and almost unusable. The rear works well on damp ground but skates when hard ground is encountered.
We raced the new T model at several local events. We won the 125 pro class at a local grand prix and finished in the top three at a couple of motocrosses. The bike was fast enough for the grand prix event but not fast enough for the 125 pro motocross class. It continually lost the drag to the first turn and was slower up hills. The T seems slower than the N of last year. Midrange power is stronger and the powerband wider but top end power has suffered as a result. Overall the bike is easier to ride with the broader powerband as gear selection is less critical. Still, no one likes to lose a race in the straights. Pro level racers will find a trip to the local tuner for porting is a necessity. Novices and intermediates will like the added torque and probably won’t need more horsepower.
Putting the handlebar into the ground in corners is easy on the T. The bike is completely neutral in corners, it will stay as low as the rider puts it. Only problem we had was a tendency to drag the rear brake pedal. Once grounded it always ends up under the footpeg and isn’t noticed until diving into the next corner, a thrilling experience to say the least.
The T is pleasant enough to ride except for the bulges from the upper shock mounts. RM owners say they get used to them but they seem so unnecessary. Other brands of motocross bikes have canted shocks and manage to design the frame so the top mounts don’t interfere with the rider.
The newest RM 125 from Suzuki is a better machine than the ’79 model but may not be good enough to maintain its popularity. Its competition for 1980 is fighting fiercely for the No. 1 spot. Kawasaki has an all-new 125 with Uni-Trak rear suspension, Honda has rethought the CR125 and Yamaha has a new Monoshock. A refined ’79 model with poor tires and a nearly useless air filter may not be enough. 13
SUZUKI
RM125
$1329
