Suzuki Rm250
SUZUKI RM250
CYCLE WORLD TEST
The Best RM Yet: Take it Out of the Crate and Win!
When the first RMseries Suzukis were introduced they drew a lot of attention. Here was a hike that looked right. Suzuki's R&D troops had finally done it or had they? Riders who had experienced the old I'M models were cautious about buying any all-out dirt bike from Suzuki. Memories of scary rides on bikes with super horsepower and little or no suspension made old injuries ache once again.
But the brave rushed out and bought the new RM hoping it would be as good as it looked. Mostly it was. Cornering was fantastic. there was lots of controllable power, long travel offset front forks, cantilevered gas shocks, a strong chrome-moly frame, trick aluminum gas tank, plastic fenders, a heavily padded narrow seat, case reed induction—the list goes on.
Still, the first edition RMs were not without fault. Stock carburetor jetting was off through most of the powerband, offering potential for piston seizures unless the needle jet was changed right away. The shocks worked well but damping faded after 15 or 20 minutes of hard riding on a rough motocross track, and the sw ing arms had a tendency to crack in front of the shock mount after a few months of hard use. Many owners had trouble with spokes coming loose and some claimed the rear sprocket was impossible to keep tight.
Aftermarket manufacturers w'ere quick to produce shocks to fit the then-odd 15M?in. length. Aluminum swing arms followed. and the combination of swing arms and shocks made the good-handling bikes almost unbeatable. Since then Suzukis have become the dominant production bikes in the 125cc and 250ce classes at most motocross tracks.
The factory noted these modifications and soon followed the first RM with an A model. Swing arm gusseting was made slightly longer and stopped most breakage problems. Jetting was much closer and the waterproof air cleaner box was designed to permit easier servicing and allow more air volume.
B naturally followed A. The bore was reduced 3mm and the stroke lengthened 3mm. A new barrel, piston and modified porting gave the stroked motor more torque. A new box section, swing arm and remote reservoir Kayaba shocks also highlighted this model.
In keeping with letter designations instead of year models, Suzuki now presents the new RM250C. OK. so what’s new? It still has the same neat aluminum gas tank with the too-small filler. Same plastic fenders that were fine two years ago but considered a little short and narrow by today’s standards. Same good seat. Same nice bars and levers. Kayaba reservoir shocks like the B had. Motor looks the same. The pipe . . . ah. the pipe is new. Longer head pipe, fatter cones and center section, and bigger silencer. Beautiful new front forks like the latest RM 125 with almost 10 in. travel. Great!
SUZUKI RM250
$1525
These long forks, identical in basic construction to the RM125B models, are well balanced in damping and spring rates. By varying oil viscosity, oil level and air pressure, these units can be tuned for virtually any riding surface or rider’s style.
Compression damping and initial spring rate are excessive, causing a nose-dive attitude over jumps, and a generally stiff ride. The rear suspension did seem to soften with use, and would probably be acceptable to most midand heavyweight riders.
Tests performed at Number One Products
Immediately apparent is the length of the sliders, necessary in order to gain travel without sacrificing engagement and rigidity. The fork internals are essentially the same as previous leading-axle Kayabas, but lengths are increased proportionately to travel. Likewise, there is that long (414in.) rebound spring which, in conjunction
with air pressure and the normal-size rebound and compression springs, produces a variable spring rate which is firm at the ends of travel, and slightly softer in the middle.
The conical front hub also is like the new 125’s. It looks and stops much better than before. The air cleaner box has been reshaped, with a wider opening at the top. Now adult-size hands can get in to change the foam filter. A Suzuki PE enduro-type chain tensioner is mounted on the swing arm and was trouble-free during our test.
One of the best changes is the owner’s manual, which is now worth reading. It explains how to adjust the Kayaba air/oil/ spring forks with accompanying graphs and charts. Complete engine teardown is shown and explained step-by-step. It’s a reference book well worth having.
The changes are impressive. Are they enough to keep the new RM out front in sales and trophies in the super competitive 250 class? Only one way to find out: Race it.
We picked the RM250C up on a Friday morning and brought it back to our shop for a pre-race inspection. We tightened the spokes (if this is done before riding any new dirt bike, spoke problems will be almost eliminated) and Loctited the engine and rear sprocket bolts. Next the exhaust pipe collar screws on the barrel were removed, cleaned, Loctited and replaced. (These will fall out the first ride unless thread sealant is used.) The rest of the bolts and nuts were checked for tightness and levers and brakes adjusted. We> filled the gas tank (using Castrol R mixed 20:1), checked the tires, adjusted the chain and handed the bike over to pro motocrosser Steve Bauer.
Bauer turned a few break-in laps at Corona Raceway, we gave the bike a quick check over, and all was in readiness for the first 250cc pro moto.
The rubber band gate shoots open, Bauer burns into the right-hand sweeper and over the infield jump the RM is 3rd. A new Yamaha YZD is leading and an RMB is 2nd. Into the bermed left-hander and Steve takes the lead. He goes in deep, shoots to the slippery inside and comes out in front. The IRC tires grip the Corona granite almost as well as European tires and the C’s stock motor has enough power to stay out front.
Watching the RM on the cobby track was enough to tell us the shocks were a little stiff (after a hundred miles or so they softened up but were still rough for anyone under 170 lb.). The forks were making terrible clanking sounds as they topped out over the jumps and bottomed in the bad holes. But even with these problems Bauer still led from the second turn to the checkered flag on a bike he had never ridden before practice.
Steve confirmed our impressions but said he had adjusted to them and preferred we not change anything. Even with the forks unadjusted and the shocks stiff, the bike flew straight over the jumps and held a fine line in the corners.
Moto two was a repeat of the first except Bauer and the C led from start to finish.
This was against a large entry of pros on well-prepared bikes. Brands ranged from Yamaha YZDs, a late-model Maico, a Bultaco, a GP Husky and many older RMs. Nothing appeared to have more power or handle markedly better.
So what did we prove? Does this mean anyone can win on an RM? No. You could easily run last in the beginner’s class without the proper training and practice. What we did prove is that a box stock RM250C is capable of winning motocross. With careful setup the bike can be competitive in any rider classification. Any competition, beginner to pro, will find it easy to ride, safe and forgiving. You won’t have to go broke buying accessories to make it handle right or go fast enough. Everything on the bike is usable as is, including the tires and grips.
Incredible. A box stock motorcycle that’s competitive in pro racing. A motorcycle this right couldn’t be any good for play riding or desert, or fire roading, right? Wrong.
We took the bike back to the shop and checked it over thoroughly. Nothing was loose or broken. We adjusted and oiled the DID 520 chain, filled the gas tank and drained the fork oil, preparatory to putting a fine tune on the adjustment. Then we read the manual section on servicing the forks. Then we read it again. It makes more sense the second time. It explains the function and has a graph showing 18 different combinations ranging from 0 to 35 psi and 9.1 to 10.1 oz. of oil per leg. (Swell. Most fork oil is sold in standard 16-oz. bottles—this means you have to buy two.)
Because the spring-only rate is a low 10 lb., the fork relies more on air pressure than previous units did. Oil volume is critical; too little will wreak havoc with damping, too much will raise the effective spring rates excessively. Too much oil can also cause a hydraulic bind, in which the forks will not compress the normal distance, resulting in shorter travel and harsher ride.
If after experimenting with these you’re not satisfied, you can try your own combination. We picked a spot on the graph that looked like what we wanted, then added 10.1 oz. of 20W Bel-Ray fork oil and 14 lb. of air to each leg.
The front end felt much better in the garage but there was only one sure way to find out. The next morning found us headed for the Mojave Desert. It’s not really a great place to be in July. Temperatures had been running 105 to 110 degrees, but we were anxious to try the bike in different types of terrain.
We unloaded, got into desert gear, started the C with one kick, and blasted off. The first thing we noticed was the powerband. The C starts pulling right away, better in fact than many 250 enduro bikes! The new exhaust pipe is responsible for most of this increase in the low end of the powerband, but there’s a price: The pipe’s increased girth means you burn your leg in a tight left turn.
Then we headed for a trail we know is full of whoop-dee-doos. The RM hit the tops of them full bore in fifth, straight as an arrow. Wow! The forks worked perfectly. They reacted easily on the small bumps and swallowed up the waist deep whoopdees like they weren’t there. It seemed impossible to make them bottom or top, and the clunking and clanking that marked their performance before the oil and air pressure adjustment was gone.
We tooled off into the rocks that spackle the desert foothills. The front wheel rolled straight and true through them. The forks absorbed the side loads and cobby surface like it was smooth ground. Even when we hit larger movable rocks at an angle the bike stayed on the intended line without trying to twist the bars out of the rider’s hands. Steering precision, augmented by the generous fork engagement and the offset axle, verges on unbelievable. The RM follows trails like it was on a rail and makes evasive maneuvers at high speed easy. The rear shocks and boxed swing arm were working almost as well as the front end, the shocks started to lose their stickiness, becoming softer as the miles slid by.
The front brake is noticeably better than before. The improvement is attributable to a longer activating arm for better leverage. The rear brake is the same cable-connected unit, not as bad as a Husky, not as good as a Yamaha YZ. When both brakes are employed, fast stops are the rule. The rear brake isn’t full floating, and produces some chatter on downhill ripples. A full floating backing plate like Husky’s would be better.
Fire roads were a blast. Whether you have a taste for full-lock slides or motocross berm shots, the RM can handle it. This is one of the few motorcycles that does both equally well.
By the end of the day we were into our third tank of gas and were still going when it started to get dark. No one could remember missing a gear in the slick 5-speed transmission, or recall having the motor bog because of improper gear spacing. Even hard-core open-class riders were impressed with the width of the powerband and the amount of power. The RM won’t stay with the new Yamaha YZD 400s but then most open bikes won’t either! It will stay right with an RM370B in a drag on level ground. This was a pleasant surprise, since the audible impression about the power is just the opposite. The new pipe and silencer have eliminated the crack from the exhaust note, making the RM sound dull and slow. One run through the gears, though, and you know you were deceived by the dull sounds.
The motor produces the best powerband of any 250cc motocrosser we have ever tested. It’s usable, not at all pipey, and strong. And thanks the 36mm Mikuni carburetor and the PEI (Pointless Electronic Ignition) the power doesn’t take long to light up. Our RMC started first kick throughout the test.
Suzuki has shunned major cosmetic changes, concentrating instead on constant mechanical updating of the RM, a policy that’s resulted in a near-perfect bike. If you’re looking for a new 250cc motocross, a desert or play bike, you’d better give the new Suzuki RM250C a good hard look.ES
