Found this on ATV Scene.com:
The first aftermarket pipe for the YFZ - The Sparks Racing X-6 Exhaust Kit
Here's some YFZ history that we're a little more sure of. Sparks Racing becomes the first aftermark pipe builder to have their pipe product ready for retail. Sparks Racing tested the YFZ on their Dynojet Dyno. In stock form they claim it put out 37 peak hp. With their new Sparks Racing X-6 Exhaust Kit, air filter kit, jet kit, and Sparks cam mods they boasted the mighty YFZ to 47 peak hp. Their biggest hp gain was on the upper end, which netted a 11.5 hp gain over the stocker. Sparks says the power was also much broader than the stock system. In riding the quad with these simple mods Curtis himself said, "it's awesome! The gain was really shocking and we are very excited about the future of this Yamaha!
The first aftermarket pipe for the YFZ - The Sparks Racing X-6 Exhaust Kit
Here's some YFZ history that we're a little more sure of. Sparks Racing becomes the first aftermark pipe builder to have their pipe product ready for retail. Sparks Racing tested the YFZ on their Dynojet Dyno. In stock form they claim it put out 37 peak hp. With their new Sparks Racing X-6 Exhaust Kit, air filter kit, jet kit, and Sparks cam mods they boasted the mighty YFZ to 47 peak hp. Their biggest hp gain was on the upper end, which netted a 11.5 hp gain over the stocker. Sparks says the power was also much broader than the stock system. In riding the quad with these simple mods Curtis himself said, "it's awesome! The gain was really shocking and we are very excited about the future of this Yamaha!


