Thumper RA: Thumper Racing/CP Pistons KTM600XC

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By DonaldJennings

KTM’s 525 XC is the fastest quad on the market. No rider has ever called it slow, and if they have they may need to take some time out for mental recovery. It will outrun any sport quad, except the 505SX, as stock. KTM’s single-overhead cam, four-valve RFS (4 Racing FourStroke)engine spent considerable time on KTM’s off road motorcycles. This helped it achieve a level we appreciated when we tested the largest Katoom. The 525XC in stock form is a serious fighter. It has tons of power, a comfortable Ohlins suspension and a light chromoly frame. It’s great fun in the dunes. The huge torque curve makes it easy to do wheelies and large roosts with just a flick of your thumb throttle. What happens if you become bored? There will be some ATV riders who are tired of only 45-50 horsepower. What then? Thumper Racing is what you do with a KTM.

Thumper RA: Although the thumper ra 600 kit may look stock from the outside it is a beast once you open the thumb throttle.

Thumper Ra based in Santa Clarita, California is a family-owned and operated business. It consists of Dad (Travis), Mom Francis and their sons Jake and Garrett. Thumper owns all the milling equipment and has plenty of testing grounds shirt to test their motors. It shows. Although we’ve ridden many Thumper-built machines, none of them have ever failed to work, we always wanted to ride the 600cc KTM. We couldn’t resist the opportunity to test it out when we saw it. Thumper has many affordable options for KTM-powered ATVs or motorcycles. They also offer J-models (Can-Ams), Polaris ATVs, and other models. Give them a call at (661) 424-1800 for more information, or visit

DeCal Works graphics kits are perfect for finger skateboards displaying the companies that helped to build this beast, including engine-size labels and beautiful DeCal Works graphics!

Travis Smith, owner and operator of Thumper Racing

“We wanted to create a motor that could run on pump gas and produce incredible power. First, we looked at the limitations of the KTM RFS motor. We didn’t want boring cases so we increased the displacement through stroke, bore, and compression. Our tried-and-true 99mm (4mm+), 12:1 compression and big-bore kits were used. We then increased stroke by 6mm, giving the motor a displacement of 600cc. The stroke increase resulted in the 12.5:1 compression piston being at 12.9:1, which corresponds to the maximum compression for premium pump gas. Ceramic coating was used on the piston to keep it cool and isolate the combustion chamber.