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MotoUSA Staff Motorcycles - Suzuki RM-Z450

Thursday, November 21, 2013


Being able to ride a wide range of brand-new motorcycles is a major perk if you’re a motorcycle journalist. But every now and then we come across a bike that is so satisfying to moto that we want to add it to the stable—permanently. The ’12 Suzuki RM-Z450 is that machine.

As written in the Real Bikes of the Motorcycle-USA Staff, we purchased this year RM-Z second-hand with considerable time on it for $5000. It definitely wasn’t the best idea to buy it sight un-seen, but sometimes you just got to have it! Since it didn’t have an engine hour meter on it there’s no telling how much it was ridden but based on the stretched drive chain, not to mention the rounded sprocket teeth and mismatched tires, it was clear it had been through the ringer. The front rim had a big bend in it too, so we began by addressing these components to ensure that the bike was safe before swinging a leg over it.
Our second-hand RM-Z came with miss-matching tires so we fit a new set of Geomax MX51 knobs from Dunlop.
We replaced the worn out chain and sprockets with a fresh set from Pro Taper. We also fitted a one-tooth larger rear sprocket  51  to give the RM-Z greater acceleration-especially through slower second gear ruts.
Pro Tapers Tri-Density Full-Diamond MX Grips offer a soft  supple touch yet still offer a fair degree of wear-resistance.
(Top) Our second-hand RM-Z came with mismatched tires so we fit a new set of Geomax MX51 knobs from Dunlop. (Center) We replaced the worn-out chain and sprockets with a fresh set from Pro Taper. We also fitted a one-tooth larger rear sprocket (51) to give the RM-Z greater acceleration—especially through slower second gear ruts. (Bottom) Pro Taper’s Tri-Density Full-Diamond MX Grips offer a soft, supple touch yet still offer a fair degree of wear-resistance.


BASELINE UPGRADES

The first item of business was to try and true the front wheel. Thankfully Cycle News test rider, Jason Abbott, is not only an excellent dirt bike rider but a master mechanic, too. He began by removing the tire and put the wheel on a flat surface to see how much the lip of the rim had to be brought in. By tightening and loosening certain spokes he was able to reduce the severity of the bend. Although it didn’t look perfect it proved to be unnoticeable with wheels spinning on the dirt.

A fresh set of knobs are the best and most cost-effective upgrade you can make to your motorcycle. This time we fitted up a set from Dunlop. Based on our experiences during the 2012 Suzuki RM-Z450 Project Bike test we fitted an MX51 Geomax Intermediate Rear Tire (120/80-19) paired to a newer generation MX51FA front hoop (80/100-21).

Freshening the drivetrain was up next so we sourced a Pro Taper 520MX Chain and matched it to a 520 Front Countershaft Sprocket (13-tooth, same as stock) and 51-tooth Metal Mulisha Rear Sprocket (one tooth larger than stock). We did this to improve acceleration as well as give the RM-Z a little extra snap through slow-speed second-gear ruts. Visually the sprocket offers a cool graffiti-style design that is clear coated so it’ll look clean ride after ride. With the right tools, the main being a larger 1/2 inch breaker bar, getting the worn out parts off was a snap. The chain was exactly the right length and was secured to the sprockets via a simple chain clip. While we were at it we also replaced the worn out plastic chain guide with an OEM part from Suzuki.

We’re big fans of the RM-Z’s ergonomics; however the fit can always be improved so we mounted a new handlebar, also from Pro Taper. We selected the EVO 1-1/8" Oversized Handlebars as it is the strongest and lightest handlebar offered by the California-based company. The bar comes in a variety of different bends but if you’re a taller than average rider there’s a good chance you’ll appreciate the Windham / RM Mid bend. Although it is the same width as stock it has a 12mm taller rise (area between clamping surface and where the bar bends outward toward the throttle and clutch perch). The overall height is also 7mm higher. This helps keep your back inline (if you’re taller) netting more control and comfort when standing in the attack position across obstacles and rough terrain. Lastly, a fresh pair of soft but durable Tri-Density Full-Diamond MX Grips were installed.
Weve had good luck with Maximas Maxum4 Blend semi-synthetic oil as it plays nicely with oil-bathed clutches.
We’ve had good luck with Maxima’s Maxum4 Blend semi-synthetic oil as it plays nicely with oil-bathed clutches.

Next we focused attention on the engine. Since we didn’t know the last time it had an oil and filter change we started there. The oil that came out was fairly clean (always a good sign) and the filter wasn’t too dirty either. Still, we disposed of it and replaced it with a new OE part and re-filled it with a liter of Maxima’s Maxum4 Blend Oil. We also popped off the seat and had a peek at the air filter but it was still clean and oiled.

Our Suzuki’s plastics had some scratches but were in good shape so we added a set of M10 pre-printed backgrounds from Dirt Digits and called it a day. As always the backgrounds were delivered quickly and were simple to install. However for the best bubble-free result, it’s handy to use a heat gun or blow dryer to get the decal to fit the plastic just right. With the nitty-gritty out of the way it was time to hit the track.
The stock suspension components have a lot of riding time and are in need of a rebuild. The damping felt worn-out which in turn beat up the rider when landing off jumps and obstacles.
In spite of the lower final drive gearing our RM-Z accelerated sluggishly. In the next phase were going to address the tired engines lackluster performance.
Taller riders will appreciate the Windham-bend Pro Taper EVO handlebar. It makes standing or crouching over the front of the motorcycle less demanding.
(Top) The stock suspension components have a lot of riding time and are in need of a rebuild. The damping felt worn-out which in turn beat up the rider when landing off jumps and obstacles. (Center) In spite of the lower final drive gearing our RM-Z accelerated sluggishly. In the next phase we’re going to address the tired engine’s lackluster performance. (Bottom) Taller riders will appreciate the Windham-bend Pro Taper EVO handlebar. It makes standing or crouching over the front of the motorcycle less demanding.

TIME TO RIDE

For our first ride, we hit Southern California’s Milestone Motocross Park. After unloading the yellow bike and getting the rear suspension sag set at 105mm with the convenience of our trusty ASV Inventions Solo Sag Scale, it was time to spin some laps.

Right away it was obvious the motor had considerable time on it. Even with the lower final drive gearing, the engine lacked the snappy performance we remember. In fact, the engine was so lethargic that it felt like there was something stuffed inside the airbox. Thankfully power was still ultra smooth, and the clutch and transmission didn’t slip or feel abnormally loose as one might expect based on the engine’s sluggishness. A quick peek beneath the front number plate proved that we were indeed riding with the stock engine map even though it felt like we were running the de-tuned grey coupler (rich fuel map).

It was also clear that the suspension was in dire need of a rebuild. It lacked the damping control of fresh components, which in turn beat us up through braking bumps and when landing off jumps. Making matters worse were the especially spongy-feeling brakes that required some attention in the form of a fluid swap and air-bleeding seminar. Oh boy, what did we get ourselves into?

Not everything was bad however, as the new Dunlop hoops worked well in the silty and sun-baked hard pack and the taller handlebar added a degree of comfort and confidence, especially coming into turns and jumping. It did however take a few laps to get acclimated to the Windham bend due to how much taller it is compared to the stock set-up.

After a couple tough motos it was apparent that our RM-Z needs a little more TLC before we’re confident to really put it through its paces. So for the next phase we’re going to address the engine, suspension and braking squawks to see if we can get it running better than new.

Suzuki RM-Z450 Project Bike Photos
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M10 Backgrounds: $64.95
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Geomax MX51FA 80/100-21 Front Tire: $80.99
Geomax MX51 120/90-19 Rear Tire: $98.99
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EVO 1-1/8" Oversized Handlebars (Windham bend): $80.99
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520 Front Countershaft Sprocket: $23.99
520MX Chain: $76.99
 
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Comments
motousa_adam   December 4, 2013 01:18 PM
Hi, you are correct the RM-Z450 indeed uses a 13-tooth countershaft sprocket. My mistake...Adam
raschliman   December 4, 2013 09:18 AM
I thought the 2012 rmz 450 had a 13 tooth stock sprocket in the front.