Bike Advice USA

Back in the day with Suzuki

Twenty horsepower. That’s the target the Big Four manufacturers had been aiming their 80cc Motocross machines back then. It was a very tough number for them to hit and make no mistake. For such a tiny Engine to crank out that much voltage means that it must produce a Mind Boggling two and a half horsepower for every 10cc of displacement. That’s pretty much on the cutting edge of reciprocating engine power output, at least in the realm of conventional aspiration.  For you to get more those day’s you, you’d have to get yourself a turbo charger, something the AMA and your competition wouldn’t be too happy about.

Now the first thing you should know is that the 1990 Suzuki RM80 didn’t hit the 20-Horsepower mark. The second thing is that it doesn’t make a shred of difference, because this bike was one of the best small-small bore machines ever to hit the track, let alone some arbitrary horse-power. And even if it didn’t crank the dyno past 20, it got real, real close.

How close would you say is close?

How about 19.2 horsepower? That placed Suzuki within range of the of the current mini horsepower champ back then, the Honda CR80, Which pumped out a great 19.4 at the rear wheel. Not only was the new Suzuki right in the hunt, it also out pulled the 1989 RM80 by 2.5 horsepower at peak output. Even more importantly, it gave the rider a user-friendly spread of torque that allows all of those horses to do more than  just make alot of noise. The RM consistently grind-ed out over 6 ft./lb. of wheel-twisting power across a 4500-rpm spread, peaking with 8.6 ft./lb.at 10,500 rpm.  In the real world torque-not horsepower-is what gets the work done, and in the RM’s case, it Delivered a Major roost from the rear wheel.

How did they do it?

By playing with the engine’s intake system . Suzuki reshaped the reed valve, short-end the intake manifold by 10mm and put a smoother cut on the carburetor air bell. Aside from a new piston and a beefed up crank pin, these are the only major power plant changes. The engine’s new intake combination produces a less restrictive  airflow environment, boosting mid to top-end power and improving throttle response across the board. But Suzuki didn’t get something for nothing; the new bike gave up a little of the ’89’s impressive bottom to mid-range thrust.

The year before 1990’s bike was stronger up to about 7500 rpm, but it pretty much got smoked by the new RM from there on. The decision to give up some bottom-end power is one mini racers will benefit from. This bike wasn’t built for trail riding. It hit hard and fast, then zooms along like a bee. Mid-range output is stunning, and there’s sufficient top-end overrun to allow the rider to choose between grabbing the next gear revving the bike those last few yards into the next corner. Speaking of shifting, the tranny got high marks for shifting action and ratios, and the clutch takes all the abuse you can give it without fading or getting grabby.

What about those brakes?

The most obvious change to the RM80’s running gear is the addition of a rear disc brake. It’s no more powerful than the drum unit it replaces, but it required less attention and delivered more consistent performance. In other words, you didn’t  find yourself adjusting the pedal height in every other moto. Another big change can be found at the rear: Suzuki replaced the 1989’s RM80 can-type Full Floater linkage with a big-bike link-style mechanism. Why? Because the cam style Floater’s moving parts had to much surface area, contributing to drag and restricting its ability to react to small inputs. This stiction was even more of a problem on the mini because the bike was so light.

The 1989 owners found it necessary to run a little more sag then normal to help the machine overcome the system’s initial friction. The new Floater allowed the rear to step right over small obstacles without compromising its ability to handle big stuff. Essentially, it preformed as well as or better the 1989 model, with a noticeable improvement in ride comfort. In order to accommodate the change over, Suzuki also refined the frame and redesigned the bike’s swing arm. Both have been made more rigid to improve handling, and the new chain guides reliability has been enhanced by the addition of aluminum brackets. It works.

What About the Front?

Suzuki knew that many RM riders were pushing the mini’s front-end hardware to the limit. So what did they do? They made it stiffer. There’s a new upper triple clamp with an extra pinch bolt, and the front axle has gone from 10mm to 12mm. Not much change, but there was a noticeable improvement. The fork was the same as the 1989 RM model but the 1990 model had refined damping, and inside each leg a single spring replaces the 1989 model’s matched set.  The tubes deliver a linear, predictable ride that was comfortable for the average 110-pound intermediate the stock bike is set up for, but the springs are too soft for hard-charging experts.

Damping is faultless, and the range of adjustments allows it to be dialed in for virtually any rider on any track. About the only thing Suzuki could have done to improve to 35mm front-end would have been to send the bike through with a set of 38 or 40mm cartridge forks. That was the next step in mini evolution, but they probably didn’t see that until 1991 at the earliest.

Does it handle good?

Yea!! The suzook manages to keep itself on the straight and narrow as long as there wasn’t to many deep ruts on the track. Because minis are so short in relation to their height, it was difficult to build one that feels as stable as a larger machine. Nonetheless, the RM strikes a good balance between stability and cornering prowess. It was a good straight line machine, and once you stuffed it into a corner the bike’s short wheelbase allows it to climb up the inside, get up-right, then quickly blast out.

Could this win in the 90’s

There was no reason why it wouldn’t win, as long as the rider is capable of winning. After all, the 1990 RM80 was a substantially refined (and substantially better) version of the 1989 best mini racer. It was quick. It handled. It shifted. It stopped. It’s good suspension and it’s well balanced. It was comfortable, predictable and geared for a variety of track conditions. It had enough horsepower and torque to keep ahead of anything short of a factory racer. And since there weren’t many of those around in the mini class, the RM80 looked like a good choice!