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Breathing New Fire Into Briggs & Stratton Race Engines
By Brendan Baker
Briggs & Stratton may not sound much like a racing pedigree to anyone not involved in karting, but to those in the know, it's a name that carries great power and respect.
Most engine builders are probably familiar with Briggs & Stratton engines, but not in racing applications - your lawnmower or other garden equipment may be powered by one of these engines. But when bolted into a go-kart, these are true racing engines, and they need the same respect and attention to detail as any other racing engine.
Karting has grown by leaps and bounds in the past two decades, spurred on by the enormous popularity (not to mention television coverage) of major league racing series such as NASCAR, Champcar, Formula One and others. Karting has long been the starting point for many great drivers in the top-level racing series and it continues to grow at a rapid pace.
Local karting clubs are in every nook and cranny of the U.S. and Canada as well as throughout the world, only you may not know about it. Therefore, engine builders may be well positioned to take advantage of the growth at the national or local level. Finding a local club to participate and support requires a little research and a trip to your local kart track.
National karting organizations such as the World Karting Association (WKA) and International Karting Federation (IKF) sanction races throughout the U.S. on almost any given weekend. Many kart racers compete on a national level, however most kart races are sanctioned by your local kart track that loosely follow one of the national sanctioning bodies' rules.
Karting is a very diversified sport with something in it for everyone. A racer can choose to run on dirt, paved ovals, street courses, full-size road courses or scaled down sprint track road courses. Most kart tracks vary in size and surface, but most tracks that are geared specifically for karting are no more than a mile in length.
Karting is also one of the only motorsports that's actually family friendly. There are entire families who go racing every weekend - together! And everyone from the 5-year-old son or daughter to the 45-year-old dad can compete. So kart racing can be very rewarding for the whole family.
Another great aspect to karting, from a racer's point of view, is that it's relatively inexpensive compared to other forms of motorsport. A complete turnkey package can be had for a few thousand dollars, and racers can usually go out a be competitive with it, depending on the chassis and engine combination of course.
Professional engine builders are widely accepted in karting, but word gets around quickly if you are not serious about the sport and the product that you build. It's all about reputation and getting customers who will keep coming back for rebuilds. And its all about respect for these pint-size powerhouses if you want to be successful.
"Briggs" engines, as they are often referred, are one of, if not THE, most common engine in karting. Some karting experts call it the small block Chevy of the karting industry. There are tons of aftermarket parts available and there have been many years of development of these engines.
Briggs & Stratton engines have a stronghold on many of the local and national classes. There are thousands of engines throughout the country on all types of tracks, so your ability to connect with the karting community will determine your success, say karting experts. To enter into this market you will need to visit the tracks, talk to racers and see what's out there so you can determine where you can fit into the sport.
There are several types of Briggs engines in karting today, with the Flathead stock Briggs engine being the most popular. Although this engine has been discontinued, there's still an ample supply of engines and parts available from aftermarket sources. The engine that is slated to take its place is the OHV Animal engine. In stock form it produces about 5-6 hp, but through modifications it can easily pump out 3-4 times that amount.
Another engine that has been promoted by Briggs and some of the major sanctioning bodies with limited success is the World Formula engine. It's an OHV engine also that was produced exclusively for kart racing using upgraded internals that produce about 15 hp. This engine, however, has not been seen as a significant platform for karting at this point.
According to kart experts, Briggs & Stratton has been pushing its OHV Animal engine, which is based on B&S's 6 hp Intek engine, on the national and local level, but the kart counts aren't coming just yet. One of the problems, according to experts, is that the Flathead engine is still a dominant force at most local tracks even though the engine has been out of production for a few years.
"I'd really like to see the Animal class take off," says Mark Bergfelt of BRE Racing Engines in Beaver Falls, PA. "For some reason in our area it just hasn't yet. One of the reasons is that people are more familiar with Flathead motors and they know how to tune them. And as long as they're around and there are parts available, people will continue to run them."
Brandon Vaughan of Kalvinator Engines in Wapakoneta, OH, says that he began running the stock Animal class at his local dirt track (Cridersville, OH), and for the majority of the year there were only 4 entries in the class, but by the end of the year there were about twice that many.
Because there are so many classes in karting not all new classes do well in the beginning, but in some areas of the country these new classes flourish. It depends on where you live, who gets behind the class and how much racers and clubs are willing to support that class.
For engine builders it may not matter so much because all Briggs & Stratton engines built for racing will need a rebuild sooner or later. One of the advantages of the Animal class for engine builders is that the kart community does not have a lot of experience with these engines yet and for those shops looking to enter this market it could be a good chance to get involved at an early stage of development.
"I have found the Animal to be a fairly durable engine," says Bergfelt. "We've never had any problems with it in stock form. It's when people started putting in big valves and cams that there were problems with these engines. I think there were a lot of broken flywheels problems in the beginning. But I really believe that problem stemmed from engine builders and racers who tried to remove the flywheel the same way as you would on the Flathead engine."
Bergfelt explains, "You have to use the correct puller. People were using a hammer to jar it loose - doing that will crack the flywheel. It's not designed to be removed that way. You may not see it but it will happen. I really believe that many of those flywheel problems were not a flaw in the design but in how people were removing them. We always used the puller and we never had a problem."
Formula 200 is not brand specific, it's specification specific. The Formula 200 class is essentially open to any 4-cycle engine that is 200 cc or under and meets the specified maximum lift requirements (and a few other rules concerning the eligibility of the Animal), but it's a fairly open and competitive class in areas where it has caught on. In California there are many clubs who are losing KT-100 Yamaha entries to the F200 class perhaps as a result of its simplicity, affordability and reliability compared to the Yamaha.
"Formula 200 is catching on somewhat," says BRE's Bergfelt. "You can run the Animal in this class based on the 6 hp B&S Intek engine, but in order for it to be eligible for F200 you have to convert it to the 5 hp Intek, which is not difficult. The only difference between the two is the crankshaft. It's the same block, but the crank has a shorter stroke, so you have to get the 5 hp Intek crank if you want to use the 6 hp Intek."
Some modifications are allowed in F200, says Bergfelt and others. "It's similar to the Limited Mod Class for the Flathead engines," explains Bergfelt. "There are some specs you have to follow such as maximum lift, but it doesn't matter what the profile is as long as it doesn't go over a certain lift. And it doesn't matter about the bore and stroke as long as it doesn't go over 200 cc. It's a nice class and it's catching on in some pockets throughout the country."
Compared to car racing and automotive engines the single-cylinder, air-cooled B&S engine is a very simple engine, obviously. However, no matter how simplistic these engines may be there is a lot of time involved on small details and in looking for little gains vs. big gains on race car engines. Experts say it is the attention to detail that makes the difference between the winners and losers and knowing what combinations work best and for what applications are the keys to success.
Profit-wise you can make pretty good money building these engines, although perhaps not as much as you could on some automotive components. "You may not make much money on the initial engine build compared to automotive counterparts," says Kalvinator's Vaughan. "If you take the amount of time I have in doing a Briggs vs. the same amount of time in a V8 or several sets of heads, I can make far more profit in the big stuff. But where you make your money with the Briggs stuff is in the rebuilds. You have to build a good engine to begin with and then keep the racer coming back for a rebuild whenever he needs one."
There are many DIYers in karting who think they can build engines only to find out the hard way that it's more complicated than it looks. A kart engine builder, as in most other forms of motorsport, needs to sell his reputation as well as his engines. The more people who see your engine on a fast kart, the more who will want you to build their engine. It's a simple law in racing: go fast and people will follow.
Prices to rebuild a stock Briggs engine vary from engine builder to engine builder, but the important factor is to charge enough for your labor and parts to make it worthwhile to you and your customer.
"Our rebuild price is $215 plus whatever parts are needed," explains Vaughan. "The $215 covers all the labor and whatever we have to do. It's the same whether the engine only needs the cylinder honed or if it needs guides as well. We have it all built in to a flat rate. We also include breaking the engine in and dyno work before we give it back to the customer."
You would think that there is not a lot to wear out in a 5 hp engine, but in race trim a fresh engine will typically last 8-10 races or so before a rebuild is needed. On brand new engines there may not be as much to rebuild but your customer won't get much extra life out of the engine either.
Vaughan says that he will work with his customer's budget to build him a motor so there is no specific set price; but of course, the more you pay the more you get. "If a customer says he needs a new engine but only has $1,000, I'll give him something for that. I've got several things I can offer. For $1,000 the engine won't get lifter bushings, or new guides, it'll basically stay stock until it's worn out. But if someone wants to spend the money, we'll put new guides in it right off the bat, and lifter bushings."
"If you buy a new engine and go run your 10 or 12 nights and bring it back to us, being that it's brand new, you'll probably only have to hone the cylinder, re-ring it and lap the valves," says Vaughan. "Occasionally we have to replace valves because racing is hard on the tips and the keeper grooves because of the kind of pressures we run. That's usually what wears out on the valves, they start getting beat up around the retainer/spring."
Spring pressure is about the most important thing in these engines. You have to play around with it to get the optimum setup, but it depends on what kind of track you're running.
"I've got customers who run Cridersville exclusively (a track known for its tight corners, where racers turn 7,100 rpm)," says Vaughan. "I've got others who run Waynesfield, which is a flat-foot 1/5 mile, turning 6,300-6.400 rpm. If they tell me they're only going to run one or the other that affects how I set the springs up. I'll go stiffer on the springs for Cridersville because I have to. If we don't, we're going to beat the valve on the head. Whereas, someone running the big track only, I'll go softer on the springs to help the bottom end. Because they're not turning as hard, they're not getting the rpms but still at peak power."
Vaughan continues: "We're trying to spring these engines so that at the rpm they're going to run the intake valve is just kissing the head. So you're talking someone running 6,300 vs. 7,000 rpm. They don't usually bend valves this way, because the valves aren't hitting that hard, but we've had some hit very hard once during a test run with very light pressures."
If you're building a restricted motor you can't just build it the same as an unrestricted engine and then throw a restrictor plate on it, according to kart engine experts. You have other factors that come into play and therefore you don't do everything you would to a senior unrestricted engine. Experts say you need to use less spring pressure, for one thing.
"Take Cridersville, a Senior Stocker revs at about 7,000 rpm, a Gold Plate is maybe 6,400-6,500 rpm, a Blue Plate is only going to see about 5,900 or 6,000 and Purple Plate about 5,300 rpm," Vaughan says. "So you have to use a lot less spring pressure in these cases.
"If I'm building a motor from scratch, knowing it's a restricted motor, I don't do a lot of carburetor work because the restrictor just kills it anyway.
"I generally hone the bores, drill out the passages (according to the regulations on size). You try to get the bore close to the maximum size, but for a Purple Plate all I do is a couple of swipes through it to smooth it out and that's it because you don't use it anyway. If I know it's going to be for a Plate motor I don't port much. I just smooth it out and port in the upper left hand corner where the air is going to go. You open that up, but you don't want to make the hole big at all, you just want to keep velocity up. So there is some difference. You can't just buy a motor and throw a plate in it and expect to win with it."
Your customer can learn in a stock engine but when it comes time to run up front you need to build an engine that is specific to the class.
Your first build should be to gain a customer and hopefully satisfy him or her enough to keep them coming back. "You have to try to make as much as you can on the initial build, but there's a lot of competition from everywhere. You are basically setting the table and selling your services as an engine expert," says Kalvinator's Vaughan.
Where is the market headed? WKA has a lot to do with where the market turns because people will generally follow WKA and IKF rules. "I think there are two things that are going to have a lot to do with the Flathead engine," explains BRE's Bergfelt. "One is the viability of WKA itself. Another is that the rules they do make concerning the Briggs & Strattons. As long as parts are available the Flathead engine is not going away. Even if WKA eliminates the Flathead class on a national level, it will still exist at the local level because that's the vast majority of kart racing. And conversely, the local level drives the national sanctioning bodies somewhat as well. They want entries and have to run what people have."
Kart experts note that racers aren't able to show up and race the Animal at every track just yet. But with the Flathead engine a racer can find a healthy class at nearly every track in the country. Industry experts say that as much as WKA and IKF and others try to influence the types of engines people run, the pendulum hasn't swung in the Animal's direction yet, and the Flathead engine looks to be around for the foreseeable future.
"WKA sanctioning OHV engines for all of its series next year won't affect us or the majority of local clubs that are separate from WKA," says Vaughan. "We're just servicing the local market, mainly. We mostly race at Cridersville, which is a local 1/8-mile dirt track."
But, experts also say it's only a matter of time before the Flathead dies out and the Animal takes over. The future for the Animal may be changing for the better, say karting experts, who anticipate sanctioning bodies going away from the Flathead engine classes and replacing them with OHV Animals as early as next year. The national classes don't necessarily dictate the direction of kart racing, but it helps to point the direction for some racers.
There is definitely a market for the Animal, and there are places where it is catching on and getting stronger. But in the meantime, the Flathead is still holding strong. Either way, opportunities abound for kart engine builders.