Suzuki Rm125

DYNAMITE COMES IN SMALL PACKAGES

SUZUKI RM125

CYCLE WORLD TEST

In the ever-changing world of off-road motorcycles, few brands remain Best in Class for more than a year or so. There has been one exception: Suzuki’s RM 125. It has been on top of the heap year after year. Being consistantly the best can turn a leader into a follower and that happened last year to the RM125. Honda's slick ‘83 CR125 out-teched and out-handled the ‘83 RM 125.

Nineteen eighty-four is a new model year, and the newest RM 125 is what most of us expected the '83 would be, a copy of Suzuki’s RN 125 factory racer.

The engine was the most disappointing part of the ’83. The 1984 RM 125 once again has a case reed. For reasons known only to Suzuki, the case reed was dropped two years ago. Suzuki’s case reed is not like the usual reed valve that fits between the carburetor and the cylinder. In the RM 125, the reed valves are positioned on the bottom of the intake port, leading to the crankcase. When fuel and air can run most easily through the piston, they do. and when the engine is wound up tight, the mixture can run right through from the carburetor into the crankcase. Most testers and racers considered the change from the case reed to the more common cylinder reed a step backward.

The carburetor is still a 32mm Mikuni but it’s the new flat-slide version that flows better than the round-slide model. There’s new cylinder porting and a heavier crank assembly. The crank weights are 3mm wider, 53mm compared with 50mm last year. The head is new with a combustion chamber shape altered for better combustion and power. The close-ratio six-speed transmission has gear ratios the same as before but the gears aren’t the same: they are made of special material that increases their strength by 20 percent according to Suzuki. Additionally, the gear‘s engagement dogs (the prongs that connect one gear to another) have less undercut. The engagement dog undercut keeps the transmission in gear. Too much undercut and the transmission won’t shift with the throttle on because the undercut pulls the gears closer together under power. The ‘83 engagement dogs had a 5° undercut angle, for ‘84 that’s been reduced 3°. There’s also a new shift stop plate that makes shifting more positive. These changes let the ‘84 RM125 shift smoother and quicker, with less effort. Finishing the list of new engine parts is an aluminum shift lever and kick lever.

The next best news is a works-copy frame. All frame tubes are large diameter chrome-moly steel. The larger-thannormal tubes are necessary because the frame’s midsection is only triangulated on the left, like the factory racers. The right side doesn’t have a tube running from the swing arm pivot to the backbone. Leaving off the right tube provides more room for the pipe and better access to the carburetor. A large airbox lives inside the triangle on the left side of the frame. An equally large foam air filter inside the airbox replaces the complex double filter used on the old RM 125.

Front and rear suspension are, naturally, new. The KYB forks have 1 1.8 in. of travel and adjustable compression damping. Stanchion tubes are 43mm, held by aluminum triple clamps that pivot in tapered bearings. The aluminum fork sliders are protected from flak by yellow plastic guards held on with yellow tape.

Although the rear suspension appears unchanged, it’s new. The aluminum swing arm is lighter and stronger, according to Suzuki. It's also half an inch longer. The aluminum-bodied KYB shock is positioned lower in the frame. Rebound damping is adjusted at the top of the shock, compression damping controls are on the bottom of the remote reservoir. Four adjustments are provided for each. Number two position is recommended as a starting position for both. The Full-Floater rockers are changed to provide a new lever ratio.

Suzuki’s RM 125 has used a single aluminum radiator for several years. The ’84 has dual radiators located low on the frame,. Nice plastic scoops direct air through the radiators and the bike comes with easily installed plastic louvers for use when the track is muddy.

Another new exhaust system is used, the better to make power. The main pipe is steel, the silencer is aluminum. The whole lot tucks out of the rider’s way and the mounting brackets don’t break.

The low-belly plastic gas tank holds 1.8 gal. of premix and is designed so the front of the seat can extend over its rear without forcing the padding skyward. The rest of the plastic pieces are new too. Works-styled fenders are wide and long. Front and side number plates have large squarish shapes so it’s not a major job trying to apply three digit numbers. Handlebars are reshaped and painted gold. The throttle barrel is still short for riders with large hands but it does come with a nice rubber cover that keeps out water and mud.

Starting the 125 is kid stuff, one or two jabs at the kick lever. Waiting for the engine to warm to operating temperatures, no vibration is noticed. Blipping the throttle tells one this RM 125 is much more responsive than the previous two models. A lot of throttle has to be used to get the 125 moving; low gear is tall and the engine doesn’t make much power below quarter throttle. Once above that, the engine comes alive. Midrange and top-end power are exceptionally strong. Gear ratios are matched perfectly to the engine’s power and there’s never any engine lag after shifting. The new transmission shifts easily and smoothly—no crunch, no hesitation, no balking. Perfect. Clutch action is smooth, quick and precise, and the lever is easily reached.

Steering is incredibly accurate, thanks to the steeper rake and huge fork stanchions. The RM never fights the rider in a turn, never tries to stand up or low-side. Changing lines to miss a crashed rider half-way through a turn is no sweat. Just steer under or go high. Deeply whooped turns are equally easy; the compliant rear suspension and deluxe forks let the bike follow the whoops without bouncing the rider around. Landing from killer jumps is soft and controlled. The bike never kicks into the air after landing, the suspension just soaks up the impact and keeps the wheels on the ground. >

Our test bike wasn’t trouble-free. After less than two hours of use the rear chain snapped. It did this without any noticeable stretching or problem. It just snapped. And it took out a large chunk of engine case with it. That's what the case saver is supposed to prevent. Instead, it may make matters worse. When a rock gets flipped up between the chain and the guard, both suffer. In the RM’s case, the case saver was pulled, with parts of the cases attached, off the motor. This required case welding before the bike could be ridden again. Without that tiny steel bracket installed, a broken chain generally breaks fewer parts.

One of our pro riders decided he’d enter the 125 class at one of the CMC series races at Carlsbad Raceway. Never mind he weighs 180 lb. without riding gear, and normally races 250 and open bikes. Never mind that no one ever races the 125 pro class with a box-stock 125 anything. He got smoked badly off the start; 125s carrying almost 200 lb. of rider and gear don’t exactly leap out of the starting gate. At the end of the 30 minute moto, our rider was a solid 5th. That generated a lot of attention and questions about the bike. The second moto didn’t go as well: the shock failed on the second lap. It suddenly lost all of its damping and the back end just bounced around after that. We’ve heard of a few RM shock failures on past models but never experienced it on any of our test bikes despite having several different models around for one-year tests. Some of our long-range RM test bikes were raced at nationals without shock problems.

Long-time 125 pro Rick Maki raced the bike next time out. He entered a 45 minute grand prix race at Corona Raceway. The course was ten miles long and included parts of the normal motocross track with the rolling hills that surround the raceway making up the remainder. All pros race at the same time, the 500s first, followed by the 250s, then the 125s. There’s a 20 to 30 second interval between starts, which are dead engine, straddle-the-frontwheel, desert type. Maki wanted to make the story interesting so he fell down in the first turn. By the end of the race he had a 1 5 second lead on the nevt 125, had passed all but two of the 250s and c open bike. Fourth overall! He was so excited v. couldn’t shut him up. The replacement shock didn’t cause any problems the second race, nor since.

The RM was totally stock the first race, the ti were changed for the second. Our test riders h; differing opinions about the stock tires. One thought they were fine, not great but fully useable; the other didn’t like them much and put on a set ol Yokohama 909s.

Saying the new RM 1 25 is incredibly competitive fun and exciting to ride, somehow doesn’t seer enough. This is the first ‘84 125 motocrosser we’vv tested so we can't claim it the best. But the other manufacturers better have real good 125s or they’L be following RMs to the checkered flag. gg

SUZUKI RM125

SPECIFICATIONS_

$1859