Go-karting – or as it is now known, karting – first gained popularity in the mid-’50s. Although backyard karts had been around for many years, it wasn’t until a couple of companies started manufacturing karts that the sport’s popularity really took off.

Karting today is an international sport. Nearly every professional driver has started his or her career in karts. Drivers like Tony Stewart, Michael Schumacher, Juan Montoya and Paul Tracy have all had successful careers in karts before moving into cars. In fact, the second place finisher in this year’s FIA Formula One World Championship, Kimi Raikkonen, had only driven 23 car races before stepping into an F-1 car. All of Raikkonen’s experience came from karting. This is a trend that is continuing in F-1 as the drivers get younger and younger and teams often lock them into contracts during their karting careers.

In the United States, karting has remained relatively under the radar, so it may be surprising to know that opportunity is so widespread. In fact there are a lot more active kart racers than most than people realize, and the sport is still growing. Karting as a whole is estimated to have 100,000-125,000 active racers in various classes and sanctioning bodies. Typical karts cost between $3,000 - $8,000, and many have highly stressed racing engines capable of propelling them at speeds over 100 mph. The fastest karts can even reach speeds up to 150 mph. Bottom line is that these are serious race machines that develop serious power from a very small package.

Karting can essentially be divided into two camps: 4-cycle and 2-stroke engines, which are mainly built for sprint racing and road racing. Two-stroke engines pack a lot of punch in a small, lightweight package and are usually built by professional engine builders who know what they’re doing. In many cases some racers build their own four-cycle motors but top running teams use professionally built engines.

Cornering The Market
Carl Woltjer was a lawnmower mechanic when he bought a stock Briggs & Stratton powered kart for his son, Daniel, in 1988. After running the first season, Woltjer decided to tear apart the engine to see what could be done. When Daniel started winning the next season, several

People asked Carl to build their engines as well. After a couple of seasons racing four-strokes, Woltjer branched out into the 2-cycle category, focusing on the Yamaha KT100. Today Woltjer Engines, Santa Maria, CA, is one of the top two-cycle engine builders serving karting.

"I don’t know exactly how many engines we do a year," says Carl’s youngest son Gary Woltjer, "but it’s in the thousands." And the most popular engine Woltjer builds? It’s still the Yamaha KT100, which has been a karting mainstay for over 25 years.

Woltjer Engines is a family business and father Carl and sons Gary and Daniel take pride in the fact that their quality engines are only built by a family member. Woltjer has two other employees; one of whom operates the dyno room and the other does engine disassembly and monitors the CNC machines.

"The only way we can build as many engines as we do and not cut corners is to streamline everything as much as possible," says Woltjer. "We cut all the heads on a CNC lathe because they’re all the same (Yamaha KT100). We don’t just do one at a time, we’ll do 10 at a time."

While the Yamaha remains the most popular, Woltjer also builds a number of other 2-stroke engines including a CR80 shifter kart engine. Shifter karts are at the top of the karting ladder with power to weight ratios equal to IndyCars or Formula One. Many professional racers keep fit driving shifter karts in the off-season or as part of a training/fitness program during the season. Shifter karts have 42-50 hp with a six-speed motocross-style sequential shift transmission and can reach speeds in excess of 150 mph!

"The 125cc shifter engines used in the Pro Moto class are open motors that can have any number of modifications," says Woltjer. "The costs are out of reach for most competitors anymore, with engines that cost up to $6,000." Consequently, he says, the Pro Moto class is almost gone from the karting scene; most karters have made the switch to the Intercontinental Class C (ICC), which is inline with the Commission Internationale de Karting (CIK), the international governing body for karting.

Stock Yamaha – Engine Builder’s Clay
The Yamaha class in U.S. karting has been around since the late ’70s in one form or another, so they are still very popular at any local sprint track and are found in abundance. One of the beauties of these engines is that racers keep finding new classes to run them. The other benefit for engine builders in the Yamaha class is that these engines are not meant to be stock. That is, a kart racer doesn’t buy a box stock engine and go racing because no racer wants to give up power. Yamahas have to be balanced and blueprinted to get the maximum performance and your average racer doesn’t have the skills or equipment to do this work.

Although the engines in these classes are the same, no two Yamahas are alike after they have been blueprinted. "Each design is a signature of what you believe is the best way to make power," says Woltjer. "We have our method of shaping the dome of the cylinder head down to a science. This is where most of the power is made and each engine builder has his own unique way of interpreting what makes that power. It’s all a combination – how you cut the head, where you put this and that. One of those things may not make a difference but all five of them together will."

It has taken Woltjer Engines many years of research and development to come up with its current designs, which are always evolving. "If you’re not getting better you’re going backwards because your competition is working just as hard as you. Especially when you’re on top," Woltjer says. "Everyone is aiming for you then."

The Woltjers have also spent many hours trackside working with drivers one-on-one to further develop their product. "You can really learn a lot from working with top drivers this way," says Woltjer. "I can spend all day working on the dyno, find out works best on it, then go out to the track and learn more. Then I take the data from the track and come back to the dyno. We just bounce off of each other."

Yamaha seems to have created the right mix of performance and quality with enough tunability left over for engine builders to shape their own way, Woljter says. Other engine manufacturers have tried to emulate Yamaha’s piston port design but have had limited success.

"Yamaha’s secret is that it’s mass produced and cheap. Where these other manufacturers made their mistake was in building a better engine right out of the box," says Mark Bergefelt, BRE Small Engines, Beaver Falls, PA. "Because they outperformed the Yamaha, you couldn’t run the two types in the same class. So most organizations created a Yamaha class and a Piston Port class. Yamaha engines could run in Piston Port with less weight so you’d get some really good Yamaha racers who could win both classes." Bergefelt says the piston port class is still around but it’s not very popular whereas the Yamaha classes are still growing. There are about five different Yamaha classes currently running at the regional and national level – 3-hole can (Jr. class), 4-hole can, Pipe, Formula Y and Spec-100.

Small Engine Specialists
Bergefelt started BRE Small Engines in 1977 as a summer job while in the service and in college. "I knew how to fix lawnmowers and karts," he says. "I asked my dad if I could use half his garage and a few years later we had the whole thing."

Bergefelt specializes in small engines, telling his customers he works on anything he can pick up and put on his bench. He has built his karting reputation on the dirt and clay ovals of Western Pennsylvania, building mostly stock Briggs & Stratton engines for the oval racing crowd. However, in the last couple of years he has been a fixture at BeaveRun, one of the top sprint kart tracks in the country located at BRE’s backdoor in Western, PA.

Even at BeaveRun, a track that is ideally suited to high-powered 2-stroke karts, the four-stroke Briggs class still has a stronghold on area karters. "In Western Pennsylvania and Eastern Ohio, I’d say that eight out of ten karters are running the Briggs engine in various types of karting (sprint and oval)," says Bergefelt. However, he acknowledges that it really just depends on where you live; California is mostly 2-cycle karts; the South is 4-cycle crazy until you get to Florida; the Midwest has a little of everything.

The 5hp Briggs & Stratton engine is often compared to the small block Chevy; it’s the most popular 4-cycle engine and probably the most raced engine in karting. For engine builders who are already doing small block work, building a Briggs will be a relatively easy transition. "The Briggs engine is much more like a SB Chevy in the way you work on them and tools that you need," says Bergefelt. "You can buy anything – aftermarket cams, heads, etc. – for the 5hp Briggs engine."

Bergefelt says he likes the variety of building both 4-cycle and 2-cycle engines but steers away from some of the high dollar 4-cycle engines. "I don’t like to do open Briggs motors because they cost too much. Around here locally, the open Briggs run in the unlimited class, which is where the much faster unlimited 2-strokes run. An open Briggs motor can cost as much as $2,000 to build. For the same money or less, you can build a two-stroke Parilla Sudam that makes over 40 hp. With the open Briggs, the very best you can get out them is 30 hp, and it will blow up. It’s not IF it’ll blow up; it’s when."

Bergefelt recommends that 2-stroke racers pressure test their engines often, likening it to a doctor’s visit. "Before your doctor will make a diagnosis he takes your temperature and blood pressure so he knows what kind of shape you’re in. If a 2-stroke engine is doing weird things, the first thing you should do is a pressure test it and rule out air leaks. They can occur so easily and will cause so many strange problems that I don’t like to make a diagnosis before I’ve done that."

Cooking Up The Right Combinations
Once you’re sure the motor will run, how do you make it run best? It’s all about the combination. "You’re trying to build the most friendly motor with good bottom end and good torque that will pull strong all the way through the top end," says Sean Cook, Cook Racing Engines, Mentor, OH "You can build one with killer top end but it just comes on too late. Conversely, you can build one that comes on very strong but flattens out at the top. It’s a compromise."

The basics are key: get the engine straight, get the case square and get the crank straight. Of course, you also have to do all of the basics of eliminating. Then the tuning, testing and development comes into play. Two-stroke experts say the magic is in the heads: understanding that unlocks the ability to play with the horsepower and the power curves.

"The port timing is a big thing," says Cook. "The cylinder head has a lot of potential for development – squish band angles and also very important is the size and shape of the hemispherical center. There are a lot of liberties in the centers and the port timing. Good engine builders know how to work these areas."

For the cylinder head, Cook says he always tries to get a particular shape, but depending on the history of the engine, he sometimes has to make compromises. "It’s like a brake rotor, there’s only so many times you can cut it," says Cook. "If you’re called on to work on an engine after a guy who put a real huge center in the head there’s not much you can do. You could weld it up but technically it wouldn’t be legal and the aluminum is so bad its often not worth working on."

That’s the downside to both 2- and 4- cycle small engines, say some engine builders: they often seem less intimidating: many people think their size means they are simple to work on and tune. While this may be true to some extent, there is still a lot of complexity to these little engines that will be too difficult for the average backyard mechanic.

Of course, this downside – anyone can open and work on one is also a reason engine builders can smile: the more engines that are out there being adjusted by racers the more likelihood that you’ll eventually get to rebuild it.

Two-stroke engines aren’t any more difficult to work on than 4-cycle engines but more people seem intimidated by them, often with good reason. "There are parts of the two stroke engine that the average racer shouldn’t work on (which is a good thing for engine builders)," says Bergefelt. "Racers shouldn’t try to rebuild their own crankshaft, for example. The fortunate thing for racers is that it’s not expensive to have an engine builder do it for you."

Cook says that coming behind work that was done by someone else can be very challenging. "The head may hold volume, it’s legal and it’s this person’s interpretation of what makes power, but to put your own spin on it, you can’t really reach what you want. I’ve had some of this problem but so far we haven’t had to go behind too many builders. I try to steer the customer to start with a new engine just to get the kind of power we want."

Many kart engine builders say they prefer to work with a brand new cylinder head because they’re like a blank canvas and you can do whatever you want. However, though Cook and others may prefer the new engines, they won’t turn work away either. "We’ll do what they want," Cook explains. "We’ll take it apart before we start to work on it and let the customer know what is needed. I’ll give them a total before we start to do work. After parts and labor, the total cost might be within a few hundred dollars of going brand new. It just depends on what condition the used engine is in as to how much has to be done."

Cook says, "There are a lot of people out there with a lot invested in engines so we definitely do what we have to do to keep them coming to us. Over half of these engines are fairly easy to switch around to our combinations. With most of the big builders, the work is very good and you can go behind them without many problems. But every once in awhile a you get an engine that’s been around for years and you just don’t know where it’s been and what’s been done."

Karting on a worldwide scale is enormous, especially in Europe. In the U.S., there are many specialized niches in karting and it really boils down to where you live in the country and what type of racing you like best. But interest is on the rise. Darrell Sitarz, president of the Kart Marketing Group (www.e-kmi.com), says that the KMI Karting Trade Show continues to grow every year. This year’s show, in Chicago February 21-22, is expected to have 33 percent more exhibitors than last year and over 300 booths.

As with all racing, to have success selling your services you must be involved with the sport. This doesn’t mean you have to go to every race but it may mean sponsoring a front running driver from your area on a regional or national level. If you are interested in racing and your kids are too, this could be a good chance to build your relationships with your kids and potential customers.

As grassroots sports go, karting is practically a movement and a way of life for those that are involved. Because of this, most kart racers and engine builders will freely share their thoughts and opinions with any newcomer. Compared to other types of racing, karting is affordable. But still, racers are racers and will spend whatever it takes to be competitive. Having a quality built engine is just part of that cost.