RG3 SUZUKI RM-Z450

few months back we did a fairly comprehensive build on our Suzuki RM-Z450. We’ve been riding and testing with this machine frequently, living with a powerplant that went way up the food chain but then became a little ornery to start. Yoshimura has since broken back into the guts of the machine and fit in some new head parts that retain the power-up giddiness, but not at the expense of an easy-to-kick-over weapon. We’ll get into the mods, how they’ve fared and, for this month, a comprehensive look at RG3 Suspension’s modifications. Rob Henricksen, RG3’s owner, is also Team Yoshimura Suzuki’s chassis boss and knows suspension. We had him valve and spring the SFF fork and Showa shock after a test ride on team manager Mike Webb’s personal machine. His fork was superb and we wanted it!

RG3 SUSPENSION—INSIDE LOOKING OUT”

RG3 Suspension owner Rob Henricksen has a long history as a suspension Einstein, dating back to his early Team Honda FMF days, his time at Rockstar Suzuki and Factory KTM, and now as the chassis guru for Team Yoshimura. It’s no secret that there are vast differences between the suspension valving and feel of the RM-Z250, which is good, and the RM-Z450, which is harsh and unyielding. Rob’s view is that, “The stock setup for many riders gives a dead and harsh feeling through the shock. It basically seems to offer little in the way of tractable control. With the fork, the action is harsh on square-edged hits and very hard to maintain a hold on around the track.”

RG3 valved it so the fork and shock were balanced with each other and  would work more in unison. Rob said, “We gave it valving that will move initially to take the spike out of the hands on little chatter bumps and, as it runs deeper, creates a progressive feel that resists bottoming without the choked-off sensation as it gets near bottoming with stock units. The fork needs much less low-speed damping, and in fact mid-speed valving and high speed were reduced also, but proportionally the change to low speed was much more significant. The single-stage valving stack was replaced with a two-stage style of valving for continuity of feel and a smoother movement through the stack. Then we replaced the stock compression valve with RG3 smart valves. These help meter the fluid flow more accurately and make the front adhere to the ground over rough terrain. We’ve found this crucial when the feeling for what’s going on positively transmits back to the rider.”

With the shock, Rob focused on giving it better feel while maintaining good full-hit function. “We retained the stock piston in the rear, and valved compression with more low-speed damping to improve the load on the front and create a better balance. Then we slightly reduced the rest of the compression stack in an effort to smooth out the action over kidney-loosening bumps. This blend of valving is critical since we need to retain a decent amount of bottoming resistance. I’m not a big fan of never-bottom-anywhere valving, as using all of the travel and getting feedback to the rider is important. The rebound damping was changed to match the compression stack and to let it reload on the small bumps without unloading on the rolling bumps. With the shock, it’s all about how it loads the fork, traction and balance with the fork. Finally, we kept the stock fork spring since the rider here was over 200 pounds. The 450 is oversprung for normal-sized pilots, so we used stock coils with six clicks of preload. Out back, we went up to a 6.0 kg/mm rear coil, setting the rider sag at 100–102mm.”

A LOOK BACK AT THE POWERPLANT MODS

The skinny on the fully modded Yoshimura motor is 95 percent positive, with one caveat: Power numbers went upwards in a strong fashion, besting the stock numbers by almost five full horsepower. But more important than the sheer numbers is the fact that the power feels lighter, quicker, smoother and then, of course, longer. This is the exact engine spec that Mat Moss used to pull several holeshots at the early Supercross rounds. The power builds strongly and cleanly and is less throbby than stock, but getting it to fire up is tougher than stock (and the stock starting was not a highlight of the RM-Z). The kick-starter feels short, lacks good leverage, and once Yosh installed its race cam and performed its head mods, the compression went up slightly, and we could never find the sweet zone where four-stroke starting ease is a must.

Yosh went back in, altered the cam profile slightly, and reconfigured the decompression zone in an effort to improve the starting prowess without killing the power. In our eyes they succeeded, and even our gimpy-kneed editors could get fire far easier.

Considering the cost of the excellent performance mods, the hard starting hurt the appeal and needed fixing. Done deal now. We understand that for 2015 Suzuki fit a longer kick-start lever onto the machine in an effort to get it KX-like (the KX450F is a super-easy starter) and that Stewart has a special lever since he, too, had issues with getting a proper kick.

A RECAP PLUS

Since the original test, we updated the wheels to Dubya Kite billet hubs fit with black Excel rims. They proved to be incredibly resilient, super tough and looked wicked. Brembo’s oversized rotor was fit up front (a necessary mod since the stock power is average at best), and Dunlop MX 31s got the nod fore and aft. This is a seriously great intermediate-based chunk of rubber.

We stuck with Vortex sprockets, though we went up one tooth on the back (to a 51). The DID 520 ERT2 racing chain performed phenomenally, stretching a little out of the hole but then maintaining its integrity after 40 hours of track time. We kept the cockpit fit with the Renthal Twinwall, though we may swap out for a bar that’s less rigid. The X-Trig clamps are no doubt our favorites, offering a little cushion and superb ergonomic freedom. We went back to a stock clutch perch (liking the feel and engagement) and then installed a Hinson actuator kit. It uses a new mounting point and different leverage, along with a new clutch arm. It made for a smoother pull and better feel. This was a good mod.

The RG3 Suspension mods proved to be superb. We got back some feel in the fork, and the hack and harshness were replaced by a positive vibe that let the rider embrace the track’s nuances without getting hammered to death. Not only was the feel rejuvenated, but the big-hit ability was retained and tracking improved, as did high-speed manners. There was less twitch, great motion through the jumps and less fatigue. In the backyard, we felt the return of “input” through the shock. It’s so dead stock that the entire chassis feels rigid, and RG3’s valving spec lets the shock move and track, improving traction, braking and the suspension balance at both ends. o