TSP Oversized Power Valve Cover – KTM Husky Gas Gas TBI

We have tested this in the UK and Europe with our race team over the past year, Wade Young has also been involved in the testing. The geometry of this cover works exceptionally well, there are plenty of other covers on the market that will do virtually nothing but look bling. See the dyno charts for bottom end power improvement, this is the most important power ‘under the curve’.

The TSP Oversized Powervalve Cover is compatible with all 250 & 300 TBI  including MX bikes.  The TSP Oversized Power Valve Cover delivers significant power gains at low throttle and mid-revs, making it ideal for trail and hard enduro riders seeking smooth power delivery and maximum torque prior to the power valve opening.

This cover can be used with both standard and aftermarket pipes.

Not only does this cover look ace, but it also increases power at low throttle and low to mid revs—precisely where most riders need it. It’s perfect for trail riders and hard enduro riders who seek smooth power delivery and maximum torque at low revs, before the powervalve opens.

Our TBI Oversized Powervalve Cover is not merely a decorative accessory. It has been meticulously designed and tested to ensure significant gains at low to mid revs. Most effective between 3000-5000 RPM, it provides a torquier feel to the power delivery at low throttle.

Check out the dyno results on our 2024 KTM 300 EXC TBI shop bike, equipped with a Medium Compression TSP head and a TSP ECU tune. The addition of the TSP Oversized Powervalve Cover noticeably increased horsepower and torque at low revs.

How does it work?

At high revs, pressure waves travelling back and forth through the expansion chamber help to supercharge the cylinder, filling it with more fresh fuel/air than it would otherwise receive. This supercharging effect and the resulting extra power is often what riders experience when a two-stroke engine is “on the pipe” at higher revs.

The downside is that these same pressure waves, which assist in supercharging the cylinder at high revs, make it harder for fresh charge to enter the cylinder at lower revs, causing a drop in power at low to mid revs. To combat this, some powervalve systems incorporate a ‘Torque Chamber’. This is a chamber on the side or top of the cylinder, opened and closed by the action of the powervalve. When the powervalve is closed or down, the chamber is open to the exhaust gases. When the powervalve opens at high revs, the chamber is closed to the exhaust gases.

At low revs, with the chamber open, the pressure waves entering the expansion chamber dissipate somewhat, losing some strength. This reduction in wave strength helps improve cylinder filling with fresh charge, thereby increasing power at low revs by mitigating the negative impact of the pipe in this rpm range. By adjusting the volume of the Torque Chamber, we can further reduce this negative impact and boost power even more. This is how the TSP Oversized Powervalve Cover enhances power at low revs (approximately 3000-5000 RPM).

To determine the optimal chamber volume, we spent months conducting dyno and track tests with various designs until we settled on one that provided a significant improvement in low to mid torque for both the 250 and 300 TBI engines.