It's human nature to want more, but when is more too much? Honestly I don't hold the answer to that question, but when it comes to power and speed on ATVs, it seems we always want a little more. With that said, wouldn't it be sweet to get 600cc out of a 370-plus-pound sport ATV? That thought prompted my introduction to a guy named Brian Schuler through a friend, Jay Clark. Brian was having his KTM 525 transformed from an already extremely fast sport quad into a 600cc monster. Thumper Racing had the task of carefully crafting this motor into a beast while maintaining its reliability. It was such an interesting process that I decided to let both Brian and Thumper's Travis Smith tell the story from their perspective.
"The KTM 525XC is an awesome machine in stock form, is a great race platform and has been winning races in all different classes across the globe. It really shines in the dunes and on the trails alike, and has proven reliable. The first performance-enhancing endeavor on this machine was to get the suspension upgrade offered by Ron Elmore at Rocket Ron Racing out of Indianapolis, Indiana. The setup consists of new valve components and different coil springs that were set up for my weight and style of riding. Once the suspension was completed, I could feel a huge difference in the improved overall handling of the KTM. This particular 525 spends most of its time in the dunes of SoCal where power is the name of the game. Anyone who's ridden one of these knows the power it possesses in stock form and understand that it's quite adequate yet not so for most die-hard power extremists.
"So the building of horsepower began in the form of the factory KTM 540 kit and the KTM 8/06 cam. I had the head initially ported by Moto Heads Racing and he installed plus-1mm Kibble White stainless steel intake valves and exhaust valves in stock sizing. Then to help keep the 540 cool I added the Minot oversize water pump. I was later contacted by Elmore at Rocket Ron to be the first one to receive a triple-rate shock upgrade on the stock Öhlins shocks for the KTM setup. I told him I was getting the SX-style A-arms for the quad, and sent the entire suspension package to him so he could mock it up on his quad and get the proper geometry mapped out for this particular upgrade. From the time I sent the package of new A-arms and shocks out, only a week went by before I received them ready to mount up. That's what I call a fast turnaround on a complete new shock setup.
"After I installed the new suspension I hauled it out to Gordons Well Sand Dunes (in California near the border with Mexico) for testing and immediately felt how good of a setup I now had compared to stock and even my original revalve job. The power of the KTM 540 was amazing everywhere in the rpm range, and the suspension upgrade was unbelievable to say the least. Everyone who'd ridden the quad in this form raved about its new handling, often saying it handled like a magic carpet. The power the 540 made with the ability of the upgraded suspension to soak any of the harsh terrains promoted confidence in the ability of the KTM. I then purchased a Precision steering stabilizer to finish out my powerhouse. Now, it will handle the logs, washed-out crevices and the rocks in the trails we ride while we are in the off-season for the dunes. As a 540 I could outrun about anything out there except the heaviest-modded quads I came up against. It had more than enough power to loft the front end easily over any obstacle that may get in your way. The power was very predictable and yet forgiving when you found yourself in a predicament where you needed to use the extra power right now. I loved the quad in this form.