Featuring adjustable compression


The Cool Head actually consists of two components, the shell (right) and the interchangeable domes (left and center). There are a total of eight domes available for each model, each one in 1cc increments.

Let Cooler Heads prevail…

Pro Design Cool Heads is one of the most popular engine mod­ifications seen on the pro racing cir­cuit. Cham­pionship motocross and TT riders Gary Denton, Tim Farr, Doug Gust, and Shane Hitt, as well as cross-country aces Barry Hawk, Chad Du­vall, and Banshee-mounted Kim Kuhn­le, have all won races using the Pro-Design Cool Head.

Top ATV en­gine tuners, such as Curtis Sparks Rac­ing, LRD Performance, CT Racing, KT Performance, Port Magic, Nac’s Racing, and many others add the Cool Head to their racing engine packages. So what’s the deal about this Cool Head? Does it simply keep the cylinder running cooler or is there more to it than that?


Well, yes, cooler cylinder temps are an important part of the plan. “Heat causes expansion,” explains Pro-De­sign’s Tom Burba, “and at a certain point in a two-stroke cylinder’s operating temperature, there’s a power loss due to the heat affecting the ring seal. By lowering the operating temperature, you get a better ring seal and therefore more horsepower.

For ex­ample, a FourTrax 250R cylinder gen­erally operates with a coolant tem­perature range of 200 to 230 de­grees, which depends, of course, on the ambient temperature. I designed the Cool Head to run at 175 to 190, which we’ve found to be an optimum range for horsepower. This doesn’t al­ways necessarily mean a move in the direction of cooling, though—some Cool Heads for certain models actually increase the operating temperature.”

Burba has 25 years of experience in the development and manufacturing of two-stroke performance products and has this down to a science. However, that’s just one of the advantages of the Cool Head.

“We also design the optimum squish clearance for each of the models we make a Cool Head for,” says Tom. The squish clearance is the distance from the top of the piston at TDC (top-dead-center) to the dome squish angle. It af­fects the en­gine’s torque and ability to rev. Stock ATV heads generally have pretty con­servative squish clear­ances, and the Cool Head’s narrower specs are de­signed for the rac­er who wants higher, stronger revs.



The really innovative part of the Cool Head is its ability to change compression and displacement with interchangeable, but inexpensive, domes. Each Cool Head when originally purchased consists of a shell and one pop-out dome.

As many as eight domes (all designed with a configuration for optimum performance) can be purchased separately, each one changing the displacement by 1cc. Why would anyone want to change a dome?

Basically, there are four reasons: to get optimum performance when there’s an altitude change, a change in port timing height, different octane levels, and fine-tuning for changes in track conditions (more torque or higher revs).

This way you can make compression changes without having to buy an en­tire set of complete heads. A bonus is the fact that if you have a major mal­function in the top end (“I done blowed my motor up, Pa!”), you can simply replace the damaged dome rather than buying a completely new head.

An experienced wrench can make a dome switch in about five to ten minutes. Certain models (like the Banshee) come with a trick O-ring seal for the head, while others stick with the OEM gasket. On top of the performance gains, Cool Heads just plain look . . . well . . . cool. Each Cool Head is entirely machined out of 6061 aircraft alloy on a CNC machine.

Cool Heads are available for the Ban­shee, Blaster, ATC 250R, FourTrax 250R, QuadRacer 250, QuadRacer 500, Pilot 400, and Polaris 400, as well as most motocross bikes and personal watercraft.


Prices range from $214 for the FourTrax 250R model to $299 for a set of two for the Banshee. Extra domes for the 250R are $39.95 each, while the Banshee units go for $69.95 a pair.

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