2010 Suzuki RM-Z250 First Ride

Steve Atlas | March 31, 2010

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Motocross is an amazingly demanding industry. With machines coming from the factory in ready-to-race configurations and new models hitting showrooms floors seemingly every time one blinks an eye, the last decade has seen an incredible amount of technological advancements. But things have slowed down as of late. With the economy falling off and the resulting slump in dirt bike sales, manufacturers have had to restructure their development process and the speed in which new models are released. And while that means less new models, there were still a few that have made some serious headlines this year – one being the all-new 2010 Suzuki RM-Z250.

We finally got a chance to throw a leg over the yellow moto machine this past week at Piru Motocross Park in Southern California. Unfortunately, it didn’t make it in time for our recent 250F Shootout, but better late than never. Why so late, you ask? Well, due to said economy, Suzuki only had a couple press units and as such we had to patiently wait our turn; a tough wait, no doubt, but one which proved to be well worth it. In fact, the number of 2010 RM-Z250s in the States is so few that the factory-supported Canidae/Rockstar Supercross Lites race team is still running ’09 bikes this year as they couldn’t get ’10s in time for preseason testing.

Under the Plastic

First thing we noticed about the 2010 Suzuki RM-Z250 was the class-leading bottom end power.Suzuki Off-Road Team Manager and now dirt press guy Mike Webb works with test rider Chris See to get the RM-Z set up to his liking.
The 2010 Suzuki RM-Z250 features a complete overhaul, sharing little to nothing with the previous model (top). Renthal bars and a slim aluminum fuel tank make for comfortable ergonomics (bottom).

Starting with the biggest change for ’10, Suzuki joins Honda as the only other 250F to be fuel-injected. Said to “eliminate bogging,” the fuel injection systems uses six major sensors to provide real-time data to the ECM for managing fuel delivery. These consist of sensors for tip over (TO), intake air pressure (IAP), crankshaft position (CKP), gear position (GP), engine coolant temperature (ECT), and throttle position (TP). ECM position has been moved as well, now located under the back of the tank for a claimed improvement in mass centralization.

Using the same outer body design as the RM-Z450, which has been fuel-injected for two years now, the RM-Z250 gets a 44mm Keihin throttle body with a 10-hole-type injector. The unit features a cold start/idle-adjustment knob on the side of the actual unit, as well as a hot start that is cable-actuated via the handlebar.

The FI system comes standard with three pre-programmed mapping settings, which can be changed by swapping out different coupler plugs that come with the bike. The coupler plug is easily accessible under the left radiator shroud and can be changed in a matter of seconds.

Standard mode, or no coupler, is for average-to-moderate riding conditions. When the optional white coupler is installed, it leans out the mixture and is designed to be used in the rain or high humidity situations, while the gray coupler richens up the mixture and is recommended for high-rpm use as well as low humidity conditions. For our test we used the gray coupler as Suzuki’s Off-Road Team Manager Mike Webb, who was on hand for our shakedown, recommended it. And after 19 years working for and racing Suzukis, we trust him.

For more constant performance, an ignition coil retainer was added for ’10, while the 250 also gets a trick new aluminum fuel tank. This allows for easy pressurization of the FI system as well as reduced weight. The new unit holds 1.7 gallons and though it looks the part, we will be interested to see how it holds up in the event of a fall. For the fuel pump Suzuki used the same unit found on the RM-Z450.

A 12-hole fuel injector with a reversed throttle valve movement is at the heart of the RM-Z450s electronic fuel injection.A Showa piggyback rear shock has both high-and low-speed compression damping adjustment along with rebound damping and spring preload.
(Above) Using the same outer body design as the RM-Z450, the RM-Z250 gets a 44mm Keihin throttle body fed by a 10-hole injector. (Below) An updated shock features high- and low-speed compression adjustability.

Though the FI is the biggest engine news, there’s also no shortage of changes under the cylinder head. New intake and exhaust cams are designed for more top-end power and feature a lightweight hollow design made from forged steel for strength. The cam profile and ECU were both changed to allow for easier cold starting as well. To retain the low and mid range Suzuki’s 250F is known for, new intake tract shapes are said to offset the top-end-heavy cam design.

A new piston features a lengthened skirt and reshaped dome, which works in conjunction with a new cylinder head gasket that is 0.1mm-thicker. The end result is a slight bump of compression from 13.4:1 to 13.5:1. To aid in reliability, a new connecting rod and crank design was employed, while an updated semi-dry-sump lubrication system and new crankcases are said to reduce mechanical loss while providing additional oiling in key areas. The new cases also feature revised placement of the oil drain holes, both now on the underside of the engine. A dual oil-pump set-up is used as well, connected via a shaft through the cases.

The 5-speed gearbox was improved to provide lighter shifting according to Suzuki, with a new primary drive ratio as well as final drive ratio. The internal gearing ratios all stay the same. And though the clutch remains mostly untouched, it does get updated springs for improved feel and durability. Expelling spent gasses is a new US-spec muffler, which is now wider in the inlet area, thinner in the middle, and wider on the exit. Keeping things cooler is a redesigned radiator hose routing system and new front louvers. The radiator itself remains exactly the same.

While no doubt somewhat overshadowed by the all-new engine, there’s no shortage of updates to the 2010 RM-Z250’s chassis.

The RM-Z250 has new radiator louvers that direct more cooling air at the twin side-mounted radiators.
New radiator louvers and updated hose routing improve cooling for 2010.

An all-new frame has been engineered with revised wall thickness to optimize the ideal combination of rigidity and flex. The engine now sits further back in the frame, nearly 7mm, while also being some 4mm lower, both aimed to pull back the CG for improved handling. Caster and trail has been updated as well, with the caster increasing three degrees (27 to 30) and the trail gaining an additional 25mm, increasing to 140mm from the previous 115mm. Steering angle remains at 45 degrees. This is then mated to a new swingarm that was designed with improved traction as its main objective, specifically through the whoops.

Fork valving and spring rates are stiffer, aimed with the racetrack and high-demand riding situations in mind. Out back, a new rear spring rate and valving shim stack firm things up and balance the bike to the updated fork.

Wider footpegs now allow for additional foot placement and more stability, combining with slimmer radiator shrouds and tank for a much smaller between-the-legs and rider-friendly ergonomics package. The rest of the machine’s plastics have been updated with a more edgy look as well, while the seat is a new cross-shaped gripper seat for additional rider adhesion.

In terms of overall specifications, the bike now features a 5mm-longer wheelbase (2170mm), while also being 10mm higher overall (1270mm), though the seat height remains the same at 37.6 inches (955mm). As for weight, despite the addition of fuel injection, the RM-Z only gains six pounds, going from a curb weight of 228-lbs to 231-lbs.

The Wait is Finally Over

To say the 2010 Suzuki RM-Z250 lived up to our expectations would be an understatement.
MotoUSA finally got a chance to throw a leg over the all-new Suzuki RM-Z250.

Throw a leg over the new Suzuki, give it a swift kick and the new quarter-liter bike comes to life with a healthy but moderate bark. Not 450-intimidating, but not soft by any means. She’s got a nice raspy voice, letting one know that what lies between your legs was designed for one thing and one thing only: Getting around the motocross track as quickly as possible. With an introduction of off-road specific models, manufacturers these days don’t try to sugarcoat anything about the current crop of MX machines. These bad boys are made for flying 30 feet in the air and winning races – whether the rider can do it or not.

Click the 249cc Suzuki into gear and head out. First lap around Piru, one thing quickly stood out: Bottom end. Where some of the 250F competition sacrifices corner-exit grunt for top end and over-rev, Suzuki does no such thing. Even with the new, more aggressive cams, which are said to increase high-rpm power, the little yellow MXer is alive the second you twist that right grip. And considering I’m not Jeremy McGrath, and tend to spend a fair amount of time in the mid-range, this came as a welcome surprise. In fact, even our Pro-level test rider Chris See commented on its benefits.

“Power is great off the bottom,” said See. “I ride a 450 regularly and sometimes getting on a 250 feels gutless, but the new Suzuki was great. Really crisp and absolutely no bog. The low end and mid range is probably the best of any 250F out there.”

Improved cornering was one of the areas where the Suzuki's new chassis helped.
Our test rider was instantly at home on the RM-Z250.

But with a big bottom end typically comes a lack of top end and over-rev. The ’09 Suzuki was well known for this. As a remedy new cams and revised engine tuning were put in place for this year. And while the end result was a healthy dose more in the upper rev range, it still doesn’t have the screeching top end that some of its red-colored competition has. That said, just grab another gear and you’re right back in the meat of the power. So while it may not rev as far, with a quick left foot one won’t lose any time to the competition.

“The motor was a bit light up top,” said See. “But considering the ample amounts of torque and the ease in which one could ride the Suzuki, you’re hardly sacrificing much – maybe a couple hundred rpm up top is all. It requires a bit more shifting, but it also pulls so much harder out of the turns that here at Piru, which is fairly tight and technical, I’d take the RM motor all day.”

We also noticed the RM-Z was a bit finicky when it came to starting it when hot; once out of sync the rider was quickly huffing and puffing. That said, when it comes to gripes there isn’t much else we didn’t like.

Handling is a bit sensitive to rider sag, but when set to 105mm the Suzuki was plush and compliant over the small stuff and did well to resist bottoming for my featherweight 140-lbs and novice skill level. Chris’ Pro-level pace and heavier 160-lb frame put more stress on the suspension and he found the fork to be on the soft side, but easily within a tunable range if we had more time to play with the clickers.

While we had to wait a long time to finally ride the new Suzuki  it turned out to be well worth it.
You can buy the bike but you can’t buy the style.

It does feel heavier than the previous model when initially cruising around the pits, but once at speed the bike’s low CG becomes conducive to quick handling and exudes confidence. Put the RM-Z anywhere you want and she’ll be there the exact moment you ask her to. The improved mass centralization also aids in keeping the bike planted firmly into ruts. The bike tracks well in a straight line as well and we had no issues with headshake whatsoever.

“Once we had the sag set for my weight the Suzuki felt really good,” See added. “It track’s dead-on straight and has absolutely no headshake, which is nice coming down the fast and choppy downhill sections here, which typically give most stock bikes fits. We could maybe have stiffened up the front with a bit more time on it, but overall the handling was one of the best stock 250Fs I’ve ever ridden; really easy to go fast on right away. Not to mention it makes from some easy whips and that’s always a plus when showing off for the ladies (laughs).”

Equally as compliant for a wide variety of riders was the Suzuki’s ergonomic package. The Renthal bars, relatively low slung seat and wide, grippy footpegs, plus the slender tank and slim shroud profile, made it easy to move around on the bike in all situations. Be it standing up while barreling down a wide-open and choppy straight, the middle of a rutted corner, or sailing over a 70-foot table top, not once did either of us catch a boot on any of the plastic pieces or feel as if the RM-Z hampered our abilities in any way. It’s a very well laid out design that works for all skill level riders.

A new frame and swingarm aid in lowering the CG as well as centralizing mass to make for a more nimble feeling motorcycle.
Would this have been the competition’s view if the Suzuki had made it to our 250F shootout?

The Bottom Line

To say the wait was worth it would be a gross understatement. With its agile turning, bottom-end grunt and ultra-stable handling, the 2010 Suzuki RM-Z250 left us with an oh-so-sweet taste in our mouths right from our first moto. Thankfully, Suzuki let us hang onto to the coveted new machine to savor that taste and really getting things dialed in. At the same time, we must say, there is still a bit of bitterness not knowing how it would have fared in our 2010 250F Shootout. If only it would have been there? No question the new Suzuki would be a potential contender for top honors.

Hmm, wait… do I smell a rematch with the shootout-winning Honda on the horizon? Guess you’ll have to say tuned to find out!

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Steve Atlas

Contributing Editor |Articles | Professional-grade speed and an attitude to match, Steve Atlas has AMA racing creds that are even more extensive than his driving record.

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