Whether you’re looking for a weekend activity the whole family can participate in or you’re thinking of guiding your offspring towards a career in motorcycle racing, the Honda CBR125R Challenge is a good place to start. In this three-part series, we’ll show you how to do it. In part two we get set with race licensing, and in the final instalment we go racing.
Part 1: Preparing the bike
Although Honda Canada no longer fields a factory Superbike team, it hasn’t abandoned road racing. Aside from introducing a privateer programme, Honda Canada worked in conjunction with national road race organizer Professional Motorsports Productions (PMP) to create an entry-level race class based on the popular CBR125R. This spec class limits modifications to reduce costs and to keep racing close; with a 14 horsepower limit, no one will run away with a win.
The CBR125R Challenge is run as a support class at several Parts Canada Superbike rounds, and has been added to the schedule of RACE events held at Shannonville Motorsport Park. Minimum age requirements are 14 years old for the national rounds and 12 years old for the RACE regionals; neither series has a maximum age limit, but if you don’t want to be called a cherry picker, leave the racing to the kids.
Transforming the CBR125R to a beginner race bike is very easy, as Honda sells an easy-to-install race kit, available through dealers. Included in the $1,500 kit is Mimic fibreglass bodywork, an Elka shock (adjustable for preload and rebound damping), an Arrow slip-on muffler, frame sliders, a race stand, class mandated sponsor decals (including an instruction sheet showing decal placement) and a coupon good for a set of class-mandated Pirelli tires. Factor in the bike’s $3,499 retail price and you’ve got a new race-ready machine for $5,000; it’s a deal you just can’t beat.
Stripping the bike of its stock bodywork and all street gear is where you should start, and on the CBR125R, this is relatively easy. All bodywork mounting bolts are easy to locate, and as an added bonus, the headlights are bolted to the fairing; removing four screws rids the bike of whole assembly.
All race organizations require that safety wire be applied to bolts and filler plugs that come into contact with oil, and that engine coolant be replaced with water. The latter is also required by most track-day clubs. Once the machine is stripped, it is easier to perform these mandatory safety modifications.
Safety wire is threaded through a hole drilled through the head of a bolt and either leads to another bolt, or to an adjacent component. It must be applied in a manner that keeps a bolt from loosening, so you’ll have to tighten a bolt to its specified torque and mark where you want to drill the holes before removing it to be drilled. Drilling for safety wire is probably the most difficult thing you’ll have to do while preparing the CBR, and you should stock up on cheap 1/16-inch drill bits; if you’re impatient, you’ll go through a bunch.
The plastic oil-filler plug was easily drilled; it was more difficult finding a location to anchor the safety wire. The footrest bracket provided a solid mounting point, but there was insufficient clearance between the bracket and frame for the wire to pass through. A clean and simple solution was to file a V-shaped groove on the underside of the right-hand footrest bracket and thread the wire behind it. To secure the wire holding the oil drain plug, a hole was drilled through a cast nub protruding from the crankcase; it was the only hole drilled anywhere on the bike. I even wired the radiator filler cap and the steering head locknut, both unnecessary for this class, but an added measure of security—and the track tech inspectors will appreciate the effort.
Most major aftermarket distributors carry safety wire (stainless is recommended) as well as the special pliers needed to twist it. Regular pliers can be used but the job won’t be as clean and it will take much longer to perform. The bolts that must be safety wired on the CBR125R include the brake hose banjo bolts, engine oil drain bolt, oil-filler plug and the front brake-caliper mounting bolts. Taking your time; this should take about one hour to do.
Coolant must be drained and replaced with water, because it’s slippery and very dangerous if spilled onto the racetrack—RACE will fine a rider if his or her machine is discovered to contain antifreeze post tech-inspection. An additive, such as Red Line Water Wetter, is permitted, and it enhances water’s cooling capability as well as lubricating water pump seals. Do not forget to either drain the water or replace it with coolant before winter storage, or costly engine damage will occur in sub-freezing temperatures.
Shock installation is easy once you’ve supported the motorcycle upright. Don’t use the supplied rear stand or the bike will drop once the shock mounting bolts are removed. The CBR is light enough that one person can hold the rear of the bike in the air while another replaces the shock. There is a notch near the shock’s upper mount designed to clear the frame and it must be mounted facing forward. This places the rebound adjuster toward the rear tire, giving limited access to the adjuster, but also making it susceptible to dirt accumulation.
A bolt-on muffler was chosen over a full exhaust system to keep costs down, but also to retain the bike’s catalytic converter. The Arrow muffler bolts in place of the stock muffler, but before doing so, you must remove a small baffle, which is held in place by a circlip. This baffle is designed to subdue exhaust noise for street use, but once the CBR is race prepped, the street is the last place it should be ridden. Note that the Arrow exhaust hanger mounts to the outside of the supporting bracket, the stock muffler mounts inside.
Cornering clearance improves if the passenger footpegs are used in place of the bulkier rider pegs. This also improves rider feel, as the rider pegs use vibration-damping -rubbers, which are too mushy for aggressive riding. The passenger peg mounting holes must be drilled larger to accept the larger mounting pins, and the inner ends of the pegs must be filed down for fit. Use both the rider and passenger-peg spring washers to retain the shorter peg’s self-return when folded upwards. Another easy mod that improves handling as well as providing a touch more cornering clearance is to drop the forks in the tripleclamps, which raises the front end. After the circlips are removed above the clip-ons, loosen the fork pinch bolts and drop the fork tubes until their tops are flush with the tripleclamps.
The freer flowing (and rather throaty sounding) exhaust should be complemented with equivalent intake modifications. Remove the airbox cover, accessed once the fuel tank is lifted, and pull the sound-deadening snorkel off. Retain the air filter; removing it will make the engine run poorly, as well as damage the engine over time. It can be modified to flow more air by removing the mesh screen, which is plastic-welded to the underside of the paper element at four points. An alternative is to order a free-flowing K&N air filter (via internet suppliers, as it is not yet available in Canada). Engine modifications are not permitted, so leave it alone. Besides, you don’t want the diminutive single to produce more than the class horsepower limit. A post-race tech inspection during the first round of the CBR125R Challenge at Calabogie Motorsports Park revealed power ranging from 12.27 to 12.95 hp, about 1.5 hp above stock. Post-race weight ranged from 242 to 249 lb; the class minimum weight is 240 lb, so be careful what you chop off.
The Mimic bodywork is pre-painted and pre-drilled. It bolts into place almost without modification; some of the holes needed light filing for perfect alignment, and the forward portion of the two-piece tail section, as I discovered, needs to be properly shimmed or it will crack when tightening the mounting bolts—a stack of washers did the trick. I also applied colour-matched duct tape between the two tail section pieces to keep it from vibration induced damage, but also to keep the rear portion from falling off—some riders reported that the Dzus fasteners unfastened while riding. The fairing belly pan is an important piece of safety equipment designed to catch oil or water in case of a leak, and is mandatory for the class. Don’t drill a drain hole into it to let accumulated water out after washing the bike. Some masking tape and a can of white aerosol paint provided the required white background for the race numbers. The supplied frame sliders bolt into holes that are already in the frame.
RACE technical manager Scott McKay helped with the development of the CBR125R race kit, and one of his goals was to make sure the modifications could be performed by anyone with basic mechanical skills. He also made sure that the bike was left mostly intact so that it could easily revert into stock form. The only part that was cut off the bike—purely for aesthetic reasons—was the rear fender overhang. A replacement fender retails for $15.
The only thing left to do is to install the class-mandated Pirelli race tires. Late autumn testing last year revealed that the best tire for a dry track was the Supercorsa Pro SC1, and for the wet the MT75. The Supercorsa is not available in the CBR’s stock sizes, so two 110/80-17 front tires are used at both ends, reversed when installed in the rear. Just show up at the Pirelli tire service centre, which is present at all Parts Canada Superbike rounds, with your coupon and your wheels, and a technician will install the tires you choose and balance the wheels.
The complete transformation took an afternoon to perform using basic tools. The only special tool needed was a pair of safety-wire pliers. The transformation is fun to do, though not nearly as much fun as riding the finished product. Take your time when working on the bike, be thorough and keep the bike clean. If you’re looking to impress rider scouts, begin with a good-looking, well-prepared machine. Riding is only part of the racing equation.
Complete class rules are found at cdnsuperbike.com.
