HITLIS YZ250

Since its initial release in 1974, I, along with countless others, believe the Yamaha YZ250 (and YZ250X) to be the best off-road motorcycle ever made. However, there is one often-cited issue with the current generation’s engine that has persisted since its introduction in 1999: it does not provide a linear power output. Additionally, no aftermarket parts have been able to offer the combination of full power and smooth control that everyone desires.

Among the many thousands of hours I have spent riding, working on, and trying to perfect these bikes, I found myself making a cutaway engine. This revealed the reason for the non-linear power delivery: spring resistance inside the PV box. While this spring resistance was necessary to activate the secondary power valves, it was unintentionally disrupting the linear nature of the governor. So, I set out to fix it.

With God’s help, I was able to envision a new system that linked the power valves to the governor while simultaneously eliminating this spring resistance. This new patented system gives the governor complete control of the power valves, and thus complete control of the power output. From there, my focus turned to the governor, and a new governor spring was created to leverage Yamaha's superior cylinder and power valve design. Additionally, adjustability was incorporated into this new governor spring, allowing each rider to fine-tune it to their liking; you can mellow it out as much as you want, or speed it up as much as you can handle. These improvements then highlighted the need to change the valve sequencing in order to make the perfect release of linear power. After trying hundreds of sequence combinations, we were able to accomplish just that.

What’s it like to ride? Simply put, it’s incredible. The bike’s acceleration and deceleration are as smooth as glass. Your newfound control of the power output makes you feel like a surgeon with a scalpel. Everything seems to work better; the traction is better, the suspension works better, the braking is more effective. You end up being smoother, which is safer, while at the same time faster and less fatigued. 

All of the components of the HITLIS kit are patented and made in the U.S.A., using the highest quality methods and materials. Step-by-step installation videos on our website make installing the kit easy for riders of all mechanical abilities. Whether you’re plunking around with the kids, in competition, or both, the HITLIS kit will elevate your riding experience. It is the first thing that should be done to these bikes.

- Tim King, Founder, Productive Power LLC