Getting the power to the ground is handled by a Renthal R-1 Works gold chain that drives the ZTR Products rear quick-release sprocket hub. The OEM hubs require the axle to be removed to change the rear sprockets, but with this setup just remove three bolts and the job is done. Keeping proper chain tension is handled by a ZTR spring-loaded chain tensioner that is mounted to the swingarm in lieu of the stock roller. The final piece of drivetrain mentioned is an RPM Dominator II axle. While plenty of companies make ATV axles, the Dominator II is by far the strongest available. Where most aftermarket axles start to break under extreme conditions and pressure, that is just the starting point for RPM's axles to consider breaking. We wanted the best products for this project, and so far that is what we've been getting.
Our test rider was all smiles...
Our test rider was all smiles after spending a few hours on the overhauled mini. The suspension and power greatly exceeded her expectations.
When it comes to the heart of our beast, we turned to Billy Holt of WRH Racing. Renowned for his dominating mini engines back East, Billy knows what it takes to get plenty of power out of these little machines and does it reliably. He completely tore down our engine and replaced all of the internal engine and transmission bearings with ceramic bearings supplied by Bearing Tech in Carlton, Oregon. He recommends ceramic bearings because they provide lower friction, increased longevity and lower heat generation than do the standard steel bearings. An additional piece that Billy recommended to include on our engine was a DC Motorsports Gen 3 slipper clutch unit to prevent destruction of the transmission and cases when landing from a jump under power.
Once the engines are reassembled, WRH installs them into a chassis to start the break-in and tuning process before they are shipped out. This gives WRH an opportunity to make sure everything is up to its standards and makes the final tuning easier once we receive the engine to install in our chassis. When it arrived at my doorstep, I opened up the box to find a plethora of goodies designed to increase the power output over stock. The first and most noticeable was the works-looking hand-rolled exhaust that had a huge chamber, looking almost as if it belonged on a 250cc two-stroke machine.
Since the cylinder was ported for better performance, the amount of fuel and air has increased as well so there were significant changes made to our intake setup on this machine. To start, the stock air filter setup was discarded and replaced with a high-flow K&N clamp-on-style filter that is installed on a 28mm Keihin PWK carburetor. To allow for this increased airflow from the carburetor to the engine, a custom billet plate was machined to fit a Moto Tassinari VForce3 reed cage from a larger dirt bike engine. This combination of intake and exhaust is designed to give the modded DRR 90 a strong pull off the bottom all the way into the top-end of the powerband. To allow the engine to quickly rev and make power, the stock ignition system was replaced by a PVL analog ignition that is used by some of the top mini racers both on the east and west coasts.
Once the engine was mounted in the chassis and given a test start, it was time to install the final parts to complete our ultimate youth racer. We received a full set of DWT Racing blue label wheels and had them sent out to OMF Performance to have reinforcing rings welded on. This combination would give us a strong wheel that is still lightweight enough for quick acceleration. To complement our wheels a set of Maxxis Razr Cross tires were mounted to both front and rear wheels for great traction. Up top a set of Fasst Flexx bars outfitted with a Pro Armor kill tether was installed, a custom steel braided rear brake line from Crown Performance joined it, and a Terrycable steel braided throttle cable went from our PWK carburetor to a thumb throttle housing that we got off of a Honda TRX450R.
The final finishing touch was the custom graphics kit made by Stuck On Racing. Stuck On took one of its standard designs and placed our logo along with logos from all of the contributors for this project in the kit. This gave the machine a super-clean and professional look. With everything done, it was time to top off the tank with VP C-12 racing fuel and Maxima Super M premix and head out to Milestone MX Ranch in Riverside, California, to put this quad through the paces on its various tracks.