Moto Ethics: RPM’s Suzuki RM-Z277 Big Bore: Integrity is in the Eye of the Beholder

By Rich Taylor

Photos by Donn Maeda

For 10 years now, Rick Peterson (the founder and brains behind RPM’s Big Bore) has morally challenged racers everywhere to bend the rules in the quest for more power. Though many will never admit it, Peterson’s services have become a staple in the professional ranks of motocross racing, and RPM’s number is on speed dial at all of the factory race shops. RPM’s specializes in building big-bore motor packages for most motocross bikes, with the bulk of their business being concentrated in 125cc-class machines. Furthermore, most of the top race teams count on RPM’s for its quality cylinder re-plating and repair services, which are highly regarded as the industry’s best. It is still the big-bore kits, however, that RPM’s is best known for, and Petersen himself has hinted that at any given 125cc Supercross or National, more than a few of his anonymous customers are on the starting line come main event time.

As if riding a 250cc machine in the 125cc class wasn’t enough of an advantage, we decided to send our Suzuki RM-Z250 to RPM’s to make our days at the races that much easier. Because the RM-Z is so new to the market, we had some concerns about the durability of a big-bore motor kit. Petersen, though, explained that the RM-Z/KXF motor had nearly the exact bore and stroke as the existing Yamaha YZ250F; a bike that RPM’s has been doing countless hours of R&D and testing on over the past three years. Basically, RPM’s had the kit for the RM-Z figured out almost before they even had a bike to play with!

CHOICES

RPM’s offers three different upgrade packages for 250cc four-strokes. The 262cc big-bore kit is a bolt-on set-up that sells for $725. For that price, you receive an OEM cylinder that is bored and plated with RPM’s specialized plating.

The 277cc big-bore and stroker kit uses the 262cc top end, but also includes a 3mm stroker crank. Since no spacer is needed under the cylinder, this is a popular kit for RPM’s and its more “ethically diverse” customers. This was also our kit of choice.

RPM’s also goes big and offers a 302 big-bore stroker kit. This kit uses the same bore as the 262 and the 277, but it has a much longer stroke. The 302 gets an 8mm increase in stroke and also gets an 8mm longer rod. Because of the increased stroke and longer rod, the 302 requires a spacer plate under the cylinder. This package sells for $2400. Ouch!

IN THE SHOP

With our choice made, Rick and his staff quickly went to work on our 277 package. The 277 kit uses a 2mm overbore piston and a 3mm stroked crank. Rick also turns down the OD of the crank so that the piston skirt doesn’t hit it, and it is then precision balanced for a smooth-running feel. He also shortens the top of the piston to get the correct deck height. This requires cutting the valve pockets deeper. It’s a lot of extra work, Rick explains, but it allows just enough room for the extra 3mm of stroke on the crank. All of the grinding lightens the inertia of the crank and piston, which actually adds to the performance of the motor, allowing it to rev more quickly.

With the 277 kit done and completed, the dyno shows that the motor spits out about 2.5 more SAE (ft-lbs) of torque, and almost four more HPs at 10,000 rpm. Those are numbers that in the 125cc class are as valuable as Bubba Stewart.

With a motor that will potentially run with the fastest of the fast, we needed suspension that could keep up. The RM-Z is equipped with a KYB shock and forks, and there is one guy we can always trust to build a race-ready setup when it comes to Kayaba components. Ross Maeda at Enzo Racing has been the industry’s KYB guru since before Swap first threw a leg over a bike. Enzo revalved our RM-Z shock and forks for professional-level racing, and spring rates were changed to accommodate a 160-pound racer. Enzo added its oft-copied Sub Tank system to the fork, which help them feel ultra-plush with exceptiol bottoming resistance.

To keep our project bike running great and well protected, we threw the Works Connection catalog at it, installing everything from aluminum throttle tubes to radiator braces to frame guards and skid plates. Though we have yet to bash into anything and put the stuff to test, we must say that all of the Works Connection products fit perfectly and are for sure the best of their kind.

FRO Systems provided a set of super-trick titanium footpegs that not only weighed much less than stock, but offered a wider platform for our boots, as well. The pegs look like bear traps with their big, gaping hole in the center, which is designed to trap no mud in even the sloppiest of conditions. Having seen Ryan Hughes race with a set of these babies on his KTM all year long, we knew that durability would not be an issue.

Finally, we installed a set of Pro Taper handlebars, as well as the accompanying set of Pro Taper triple clamps. The clamps feature a unique multi-position handlebar clamp that allowed us to fine-tune our bike’s ergonomics.

ON THE TRACK

The first thing we noticed when we fired up the yellow monster was the incredible response of the motor. At just a crack of the throttle, the 277cc RM-Z launches with a violent, yet smooth attack. The great and unique character of the motor is that after that initial launch, it continues to pull and rev farther than any 250cc four-stroke we’ve ridden. It has a broad power band that was easy for our less aggressive testers to make good use of, yet enough spunk to bring a smile to our fastest test riders’ faces. Second gear starts are not a question on the RPM’s RM-Z277; even in deep, heavy dirt, the bike would consistently stay on the pipe and pull hard. We knew all of our notions about the 277 were spot-on when we jumped the entire double to table on the big track at Lake Elsinore MX Park. This is a 120 foot step-over jump that only big bikes and some top-level small bore riders consistently get all the way over. On the RM-Z277, we could bobble in the turn before the jump and still easily downside the landing, every lap.

The suspension was equally as impressive. The LEMP motocross track is stocked full of Supercross-style obstacles with outdoor speed in between and rough braking and acceleration bumps all around. The Enzo-modified shock worked superbly in the chop and normal sized hits and remarkably, the bottoming control was also right in the ballpark. We could hammer into the faces of jumps without even a hint of a clank, and driving out of corners was smooth as silk with the settings in the shock.

The performance of the forks came as no surprise to us. We have been using the Enzo Sub Tanks since—well, way before you had even ever heard of them—and it’s obvious why all the top privateers in the country have them on their bikes. The Sub Tanks allow the forks to work as close to factory components as physically possible without actually seeing green on your sliders. Yes, they are that good! The bottles allow you to run a higher oil level for bottoming resistance, without feeling the harshness in the small chop. What can we say; we had no complaints with the Enzo Racing-modified cushions.

Let’s face it; the fastest guys on the track are usually the fastest guys on the track no matter what they are riding. If Ricky was on a stock CR250R at any national, he would still be battling with the top guys. Sure, his race bike is head and shoulders above all but the other factory bikes, but the bottom line is that he is also head and shoulders better on the bike than anyone else. What’s our point? Just that no amount of added power can make up for a deficiency of skill, but it sure can make life easier and more fun. The RPM’s RM-Z277 won’t automatically turn you into a winner, but it might help improve your results a little. We here at TWMX would never endorse cheating, so let’s just say that for a vet-class rider who prefers the small-bike flickability of a 125cc-class machine, the RPM’s RM-Z277 kit is the easiest was to make your Suzuki (or Kawasaki) thumper into the perfect weapon. As for the rest of you 125cc-class racers, let’s just say that how you sleep at night is none of our business…

PARTS IS PARTS

RPM’s Big Bore 277cc Kit $1800.00

Enzo Racing Fork and Shock Mods $510.00

Enzo Racing Sub Tank System $350.00

FRO Systems Titanium Footpegs $TK

One Industries Tecnoflex Graphics $59.95

One Industries Grip Seat Cover $49.95

Pro Taper Handlebar $89.95

Pro Taper Bar Pad $16.95

Pro Taper P3 Upper Triple Clamp $169.99

Pro Taper P3 Lower Triple Clamp $159.99

Works Connection Radiator Braces $55.00

Works Connection Skid Plate $66.00

Works Connection Reservoir Cap $24.94

Works Connection Aluminum Throttle Tube $49.95

Works Connection Rear Caliper Guard $27.50

Works Connection Oil Fill Plug $22.00

Works Connection Frame Guards $59.95

Works Connection Engine Guards $99.95

CONTACT

Enzo Racing 714/541-5210 www.enzoracing.com

FRO Systems TK

One Industries 619/263-9880 www.oneindustries.com

Pro Taper 909/736-5369 www.protaper.com

RPM’S Big Bore 626/967-3052 www.rpmsbigbore.com

Works Connection 530/642-2174 www.worksconnection.com

Caption

ACTION SHOT CAPTION

Rich Taylor has ridden plenty of works bikes in all his years of test riding, and the fact that he was so impressed with the RPM’s Szuuki RM-Z277 speaks volumes about the bike’s potential.

 

 

 

 

he small-bike flickability of a 125cc-class machine, the RPM’s RM-Z277 kit is the easiest was to make your Suzuki (or Kawasaki) thumper into the perfect weapon. As for the rest of you 125cc-class racers, let’s just say that how you sleep at night is none of our business…

PARTS IS PARTS

RPM’s Big Bore 277cc Kit $1800.00

Enzo Racing Fork and Shock Mods $510.00

Enzo Racing Sub Tank System $350.00

FRO Systems Titanium Footpegs $TK

One Industries Tecnoflex Graphics $59.95

One Industries Grip Seat Cover $49.95

Pro Taper Handlebar $89.95

Pro Taper Bar Pad $16.95

Pro Taper P3 Upper Triple Clamp $169.99

Pro Taper P3 Lower Triple Clamp $159.99

Works Connection Radiator Braces $55.00

Works Connection Skid Plate $66.00

Works Connection Reservoir Cap $24.94

Works Connection Aluminum Throttle Tube $49.95

Works Connection Rear Caliper Guard $27.50

Works Connection Oil Fill Plug $22.00

Works Connection Frame Guards $59.95

Works Connection Engine Guards $99.95

CONTACT

Enzo Racing 714/541-5210 www.enzoracing.com

FRO Systems TK

One Industries 619/263-9880 www.oneindustries.com

Pro Taper 909/736-5369 www.protaper.com

RPM’S Big Bore 626/967-3052 www.rpmsbigbore.com

Works Connection 530/642-2174 www.worksconnection.com

Caption

ACTION SHOT CAPTION

Rich Taylor has ridden plenty of works bikes in all his years of test riding, and the fact that he was so impressed with the RPM’s Szuuki RM-Z277 speaks volumes about the bike’s potential.