Some inventions, tools, and techniques have advanced the sport of motocross significantly since their inception. The Racer X staff explains some of those advancements in this feature, “Next Level,” and this month, we spoke with renowned championship mechanic, Mike Gosselaar. "Goose" is known for his work with riders such as Steve Lamson, Ezra Lusk, Ricky Carmichael, Ryan Dungey and Chad Reed, among others, but for this story we asked him for info on one of the biggest game changers in the history of internal combustion engines: liquid cooling.
Liquid cooling is a subject Gosselaar knows plenty about. Before it was even a feature on production motocross bikes, he’d already been experimenting with it on his own, creating a working system on his YZ125 with a helicopter oil cooler he’d salvaged from a nearby aviation scrap yard, as a radiator.
“Air cooled cylinders had fins on them to dissipate heat, and we machined off all the fins, except for the bottom and top fins,” Gosselaar recalls. “Then we welded a jacket around it, and I took some aluminum fittings and welded them on there, one high and one low. The water would come to a boil, which is too hot compared to nowadays, then it would go through the top hose, get to the oil cooler I had mounted on the forks as a radiator, cool off, and go back down. It was a continuous cycle. It would just kind of percolate, kind of like a coffee percolator.”
It’s impressive that Gosselaar, who was just a kid working at bike shops at the time, had the drive and ingenuity to even attempt something like this, but even more impressive, it worked really well!
“I couldn’t believe how much faster my bike was, and consistently faster too,” Gosselaar says. “That bike just ripped compared to other bikes. It was really amazing.”
But why? Well, there are several critical factors at work here, but probably the most important was that it allowed the engine to run much cooler, and a cooler engine means less expansion, which reduced undesirable things like blow-by (power escaping around the sides of the piston instead of pushing it down following combustion).
“Air cooled bikes lost so much power as they got hot,” Gosselaar added. “Blow-by, detonation, everything. It all got worse on air-cooled bikes from the second they started to warm up.”
Another important factor was being able to keep the engine in a narrower temperature range, and ideally, within a target temperature zone ideal for reliability and performance.
“It keeps it much closer to where it needs to be, in a target temperature range, both for the life of the engine and in order to maintain consistent performance,” Gosselaar explains. “There was less expansion and contraction, and engines were able to be built using tighter tolerances, and leaner, more efficient fuel mixtures were able to be used. And if you raced air cooled bikes in the mud, it would come off your front wheel and clog up the cooling fins on the leading edge of your engine and it’d get really hot really quick.”
In other words, liquid cooling provided a much more stable platform that allowed engine builders to create much higher performing machines. Consistent cooling had another key advantage, especially for durability.
“Air cooled engines didn’t cool consistently around the whole cylinder either,” Gosselaar explains. “There would be hot spots and colder spots, which would create wear spots. Engine durability is much higher with consistent cooling and lower temperatures. It just offers huge benefits.”
There are some disadvantages to liquid cooling, such as a more complex cooling system with more parts that can fail, more weight, and in most cases, a higher center of gravity, but those minuses are far outweighed by the advantages of liquid cooling. In fact, when asked if it’d be possible to produce the high-performance engines of today, particularly four-stroke engines, without liquid cooling, Gosselaar was quick to respond, “I doubt it. I could be totally wrong, but I really don’t think so.”
Like Gosselaar's hand built water cooling design, there were many experimental designs before liquid cooling made it to production bikes, and even the first production bikes had flaws (Yamaha sold a bike with the radiator attached to the handlebars, behind the number plate). By the 1980s, though, liquid cooling had taken over, and performance went to the next level.
