Suzuki fans have always been hard-core. Going back to the DeCoster heyday of the early ’70s, some riders have had near-spiritual devotion to the brand. Back then it was easy; Suzuki won more than any other manufacturer in those days. Now it’s more difficult. The stats for the RM-Z250, in particular, are a little disheartening during the past 10 years. Outdoor championships won: 0. Regional Supercross Championships won: 0. Outdoor National races won: 0. Regional Supercross races won: 2. And yet, the RM-Z250 is still loved by many. It’s a bike for the purist. It’s inexpensive, reliable, well-behaved and free of the complications that come with an electric starter and a battery.
The 2022 Suzuki has a lot going for it, but sheer performance isn’t on the list. Peak output is a tick under 40 horsepower, whereas something with a KTM motor is around 44. The good news is that the motor hasn’t changed in a while, and there are lots of shops that know how to get the most from it. For this project, we took the path of least resistance and asked Pro Circuit to help. We knew they knew what to do.
MOTOR MUST-HAVES When we say the RM-Z motor hasn’t changed in a while, we mean it hasn’t changed much for the better. It did get some new top-end parts in 2019 and more extensive changes back in 2016. Sadly, those updates were not effective enough to allow the Suzuki to keep up with the rest of the class. The modifications that Pro Circuit was doing all along had more impact. These have four major components: head work, camshafts, a high-compression piston and an exhaust system. In order to install Pro Circuit’s cams, you must use stiffer valve springs. The good news is that, in order to use the piston, you do not need to run race fuel. It’s certainly a good idea; higher compression always puts you at risk for detonation. High-octane fuels battle that and allow the motor to run cooler. In some cases, race fuel can also provide more horsepower, although that can get expensive. We decided that the ETS ExtraBlaze 100 was a good match for this engine build. It’s rated at 100 octane and is lightly oxygenated (3 percent), which is well within AMA guidelines and doesn’t require remapping. It’s also much, much more affordable than the exotic fuels run by factory teams. We also installed a Pro Circuit T-6 full exhaust system. We did not change the ignition to one of the options typically used in an all-out, cost-is-no-object build. At some point you run into diminishing returns with any four-stroke build. If we had bumped up the compression higher and elected to run a more exotic fuel, a programmable ignition like a Vortex or GET would be mandatory. Then would come a long process of testing and programming. With a moderate build like this, we felt we could get away with the Suzuki’s three coupler-based mapping options.
The only other part of the motor that we changed was the clutch, which was swapped out for a Hinson basket combined with Pro Circuit springs.
We still love the way the Suzuki RM-Z250 handles. Yes, we know it’s a little heavy for a bike with no electric start. Yes, we know it has an old-school feel. But, to be honest, we kind of like that old-school feel. Suzuki was way out in front of the other manufacturers back in 2008, with quick steering geometry and a well-planted front end. In the decade that followed, everyone tried to copy Suzuki’s formula, then overshot the mark. Today’s 250s are much more nervous, while the Suzuki still has a comfortable, stable feeling in the corners. Where the RM-Z can really use help is in the suspension department. The current bike has weirdly mismatched settings and actually isn’t quite as effective as it was back in 2016. The front end is stiff and the rear end is loose. Neither is a terminal problem, but you can’t necessarily fix it with clickers. Pro Circuit’s suspension department has dealt with hundreds of Suzukis. What you need depends on how big you are and what kind of riding you do. You might be able to get away with the stock fork springs, although most younger, lighter riders in the 250 class need lighter springs.
You can also make some headway in the chassis department with different engine mounts. The stockers are very rigid, and Factory Chassis Parts (FCP) has replacements that give the frame more compliance. Swapping out the stock bars for Mika Pro Series handlebars and having MotoSeat rebuild the saddle also helped make the Suzuki a more comfortable bike.
In the end, did we have a bike capable of ending Suzuki’s dry spell in pro racing? No, but we did have a bike that was an absolute blast to ride. The RM-Z250 went from being the penalty bike in the 250 class to a machine that is capable, even likely, to win at the sportsman level. We closed the gap in motor performance to the Austrian-powered 250 motocross bike, and virtually any rider would agree that the Pro Circuit RM-Z250 handles better than a stock KTM/Husky/GasGas.
Having said that, Suzuki haters will still point out that the bike has no electric start and that it isn’t fair to compare a modified RM-Z250 to stock bikes. Even though you can buy a Suzuki for thousands less, we admittedly put those thousands right back into the bike.
If you’re punching the buttons on your calculator and doing the math, you’ll find that the numbers aren’t kind to a project like this. We’re okay with that. If you’re a fan of motocross history and want to keep your personal Suzuki legacy alive, it isn’t about the numbers, and we love the result.