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UAS has some of the most open rules in kart racin...
The current race engine that Briggs & Stratton of...
Chinese “clone” engines have sprung onto the kart...
Some tracks run a $150 claimer rule to try to kee...
Kids rule karting and the Cadet class is one of t...
The flathead engine went for $150 a decade ago at...
Karting Engine Market and Technology
Though it has been out of production for about eight years now, and the last of the kit motors went away about two years ago, the Briggs & Stratton flathead engine, the original L-head design engine, is still the most popular 4-cycle engine in kart racing, according to karting experts.
By Brendan Baker
Experts say that the situation isn’t getting any easier for flathead lovers because many parts and pieces, such as flywheels and sump covers, are not manufactured anymore. There are, however, some replacement parts on the market that are manufactured in China such as sheet metal and valves. Burris now makes most of the pistons for the flatheads but only has about half of the sizes that used to be available.
About ten years ago the Briggs flathead engine went for $150 at a local tractor supply store and now karting experts say a competitive blueprinted flathead goes for $1,400 - $1,600. In fact, enthusiasts say that you’d be really hard pressed to find all the parts you need today.
“Most guys are building new engines with a used sump cover and a used flywheel and as many aftermarket parts as they’re allowed,” says Brian Carlson of Carlson Racing Engines in Linden, IN. “That includes piston, rod, cam, lifters, valves, springs and sheet metal all being aftermarket and carburetors from China. There’s just so little of the original motor left, which is why it costs what it does now. It’s more expensive than an Animal engine that you can build brand new and make 50 percent more horsepower yet isn’t as popular.
For the last eight years Briggs & Stratton and the World Karting Association (WKA) have been trying to wean racers off of the flathead because they are no longer supported or manufactured for industrial purposes.“Flatheads were no longer a good seller and have faced restrictions from the EPA, which kind of forced Briggs & Stratton to go into the overhead valve market (OHV), a market that Honda has dominated for years on the OEM side,” says Carlson. “Chances are if you bought a generator or power washer or some other industrial piece of equipment, it came with a Honda OHV engine. The Honda 5.5 motor completely took over that market, so Briggs addressed that with their Intek series of OHV engines, which is OHV.”
The current race engine that B&S offers is an offshoot of the Intek called the Animal. B&S has been hoping against hope that this would be the engine to take the place of the beloved flathead but it has been slow to take off. “The Animal was designed from the Intek but has a little bit different cylinder head, a racing connecting rod and a little bit better carburetor,” says Carlson. “This is the engine they have been pushing to karters for the last eight years. It’s been like getting Toyota into NASCAR. There are a bunch of guys who have the flathead technology down and don’t want to change.”
The latest class to enter the karting market is called the clone engine class. About three years ago Chinese companies started cloning the Honda OHV engine, which led them to be coined the name “clones.” According to our kart experts, these engines have gained tremendous popularity in recent years for budget-minded racers.
“It’s a 6.5 horsepower copy of a Honda engine that I sell for $135. How can you go wrong for that?” says Mark Bergfelt of Bergfelt Racing Enterprises in Beaver Falls, PA. “You run them and blow ‘em up and get a new one. I’m going to have to start blueprinting them soon because that’s where the bulk of the 4-cycle dirt classes are heading. You either run them blueprinted or as a claimer. At Beaverun we do it as a claimer for $150.”
If a track wants to keep the class truly stock and low cost then the claimer rule works well. Some karters think that blueprinting takes away from the spirit of the class in some ways but depending on what your local track adopts, kart engine builders may see more of these next year.
“The quality of the clones is pretty poor and it varies from one engine to the next,” Carlson explains. “The original intent of the class was to take guys who had go-karts sitting in the garage and weren’t racing for a year or two to come out and run them. Some guys had outdated equipment and couldn’t afford the latest Briggs & Stratton engines. But they could buy a $99 motor and a cheap drum clutch and then go racing for fun. Some tracks adopted a couple of differences in the rules, and some had a tire rule, but it was supposed to be a cheap beginner-type class. You could buy a used kart and put this motor on it and race it for under $1,000. That sounded great to a lot of former racers.”
However, it didn’t take long before clone guys began showing up with brand new karts and $450 sets of cut wheels and tires. The karts became so underpowered that naturally people got “creative” with clones, says Carlson. “So a $100 engine turned into a $300 engine, which turned into a full blueprinted engine for $800. And now we’re looking at $800 for a clone that is essentially a full race blueprinted engine class, and the last thing karting needs is another class because it’s already very fragmented.”
An example of a class where the engines were supposed to have been stock but karters couldn’t leave them alone is the Cadet class that runs little 50cc Comer two-stroke engines. “Comers are a weed trimmer motor and racers have been the worst enemy by cheating up these little engines,” according to Carlson. “That’s just the way racers are, they want an advantage. Crate motors may work initially but eventually people find tricks.”
Mark Bergfelt agrees. “There are some guys with stock motors spending $3,000 on them. I really think the fairest way to run Cadets is stock-appearing because there’s no politics involved. There’s only so much you can do.”
Bergfelt says that two-thirds of the engine work he does is with the little Cadet engines, where the Comer 50cc is very popular. “The places where it is run as stock-appearing, those tracks I own: my motors do very well in that type of class. I do a lot of things to them like porting and carb work but I can’t say exactly because they are my secrets. I put some of what I did on my website and a lot of people copied it so I stopped doing that.”
Bergfelt says he pioneered a cut flywheel because it helps the Comer rev quicker and helps keep the engine hot, so it solved both of those problems. “People used to send me their flywheels but anyone with a lathe can do it really. After other people caught on I quit getting those orders. Then I made a mandrel to true the cylinders. I put that on the website also and stopped getting the orders for that also. After people figured out how I did it they quit sending their stuff to me. Right now I’m building a lot of clones and open class UAS two-cycle motor builds. A lot of the top two-cycle guys are running my engines.”
Bergfelt’s other duties when he’s not building kart engines is heading up the Unlimited All-Stars series, so he has his hands full right now he says.
“UAS has gotten to be so big and officially I’m the Executive Director in actuality I own the copyright to the rules,” Bergfelt explains. “I started the series 20 years ago and it’s grown to over 20 regions around the country. The UAS has become the standard rule set for open class racing especially in speedway oval racing. There are some tracks that adopt variations of the rules to fit their needs but use the UAS rules as a basis for open class.
Bergfelt says the dimensions of what engine sizes are eligible are the maximum allowable by insurance companies for go kart racing. Everything else is based on a handicap formula for the various styles of engines. You can download a copy of the rules at www.unlimitedallstars.com. UAS has had a national ranking system since 2007, with four national races and the 6 best regional finishes and 2 best national finishes counting towards overall points. From an engine builder’s perspective, the open rules of UAS are very enticing.
“We encourage people to build crazy stuff. It’s the exact opposite set of rules than that of most other types of karting, meaning very limited and restricted,” says Bergfelt. “You really don’t want to go too big, especially indoors, because you can’t use the power. The nationals are always on a track that’s around 1/5 mile, which is what I like it to be. If it gets too big then it becomes all horsepower and if it’s too small, horsepower doesn’t matter at all. So 1/5 mile is the happy medium where everything matters. You can make a lot of engines work and be competitive with a track that size.”
UAS has some of the most open rules in kart racing and among the widest variety of engines in use, including a Wankel that is manufactured in Germany. “Wankels are allowed up to 300cc,” says Bergfelt. “Right now that engine is in the 50-plus horsepower range and it runs heads up with a 450 motocross engine that pumps out about 70 hp. They will run pretty equal because there’s so much power with the motocross engine that it’s hard to put the power down. You’ll get guys running 200cc twin engines that can pump out 70 hp. At the Grand Nationals, if you could imagine it, it was there.”
CRE’s Carlson has also built some wild UAS engines. “We just did a Honda GX390 which starts out life as a 13 hp OHV engine. When we were done it was right at 40 hp. It was a neat engine on the track all torque. When we did the dyno run on it the torque curve was flat from about 3,000 rpm to 5,500 rpm. The customer asked where to set the clutch and I told him wherever you want!”
Carlson explains “That particular engine had a CNC billet head, big valves and the ports were moved over. It was a completely different head from the get go; it had roller rockers, longer chrome-moly pushrods, a billet rod, JE piston nice, nice pieces in it. There was very little stock when we were done. It made a great engine and if you were to build one new it would run about $3,500. It’s a handful to drive something like that. It’s 4-cycle and mostly made in the U.S., too.”