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MotoGP today is a highly evolved and scientific competition where electronics play a vital role in delivering power to the road and adjusting the balance of the motorcycle to maximize the engine’s performance.

This year there are three American MotoGP riders – Nicky Hayden, Ben Spies and Colin Edwards – who all started their careers in AMA (American Motorcycle Association) road racing before moving up to the world stage of MotoGP. They honed their skills on bikes you and I can buy off the showroom floor and ride down to the local coffee shop or watering hole. These bikes may ride on the streets but they are more at home on the race track.

Today’s sportbikes are born and bred from more development in racing competition than anything else, and are, essentially, racing machines with turn signals and headlights.

Manufacturers have come up with very impressive production sportbikes for sure, but that doesn’t mean there’s nothing left for engine builders to develop. While road racing may not be at its healthiest these days, mainly at the pro level, there are still a number of club racing series around the country to keep sportbike engine builders busy.

KWS Motorsports is an engine and bike builder out of North Charleston, SC, that keeps its 5,000 sq.ft. shop busy pumping out engines and bikes all year. “We build a lot of engines and complete bikes for club racers, pro racing, street bikes and drag racing. We also build a lot of motors for car racing applications,” says KWS’ Chris Spalding. “We build a lot of DSR and CSR motors for SCCA sports racers and also some Mini-Sprint applications. We do a lot of 450 singles for flat track racing. If it’s motorcycle-powered, we are involved. We are pretty diversified in most of these markets.”
KWS has been in business since 1994 but owner Kevin Hunt has been a motorcycle racer since 1982. “He got into the AMA expert class as a semi-pro and then went into the Navy and did some automotive stuff as a tech,” says Spalding. “He started building motorcycles on the side because he was a racer. And as people tend to do, he started selling parts out of his garage and then he outgrew the garage. Today we have six employees operating out about 5,000 sq. ft. It’s not very big but we make it work. Motorcycles take up a lot less room than cars.”

Spalding says the shop’s location is within a day’s drive to several tracks. There are seven tracks within a six hour drive. It helps them service their customers a little easier. The WERA Southeast Region is by far the strongest club racing series, they have 15 events, which for a regional series is a lot of races.

The motorcycle drag racing market around the region is very strong as well, and Spalding says about 50 percent of KWS’ business comes from building Suzuki Hayabusa drag racing engines. Hayabusa’s are built really well for drag racing applications and have remained essentially the same engine from ’99 to present. They had a major update in 2008 but most of the engine has remained the same, according to Spalding. The motor is based on Suzuki’s old SRAD technology from 1996, which is the GSXR 750 with Suzuki Ram Air Direct. That generation of GSXR was dumped but Hyabusas evolved from there and have continued to thrive. Hyabusa engines have an older style architecture with a separate cylinder than the head and block, in contrast to most of the modern sportbike engines that are designed as one piece to reduce weight and increase structural rigidity.

“The evolution of the Hayabusa started out as a 1,299cc engine back in 1999 and now the biggest version we build is a 1,720cc,” explains Spalding. “It’s a 5 mm overbore with an 11 mm overbore stroker crank. Turbos for these engines are very common. We don’t do any turbos here but we build the motors and hand them off to people who do install turbos.”
KWS designs its own custom pistons working with such companies as Wiseco, JE Pistons and CP Pistons. Spalding says CP does most of its custom pistons right now. “We are doing stuff for stroker application where we’re moving the wrist pins around. Depending on the class, we do some stroker engines for road racing. There are some classes, like WERA F1 for example, where the rules are open and you can do whatever you want. In that kind of application we usually use a GSXR1000 engine, but it’s so easy in that type of class to build something that’s almost unrideable. We used to do the WERA F1 race at the Grandnationals every year when we were a Suzuki-sponsored team. Most of the time we build a 1070cc GSXR1000, which is a 3 mm overbore, but the last time we raced this bike it made 215 hp and 115 lb.ft. of torque. It was pulling the front wheel clicking into sixth gear, and it pulled wheelies coming down the hill going into the esses.”

Splading says the key to success isn’t just big power, its being able to put the power to the ground in a road racing application. “We’ve gotten to the point with engine technology where, and you see it in all forms of motorcycle racing, where making the power is not as important as making the power useable. The bikes are violent and will throw you off in a hurry if it’s not right. What you do with electronics, cam timing and compression, help to make it so you can ride the darn thing.”

Spalding says the GSXR model line is by far the most popular bike for road racing. “It’s the most supported by the aftermarket and it’s been around for a long time, there so much interchangeability between the bikes, the 600, 750 and 1000 bikes, and Suzuki is really good about evolving them instead of starting with a clean slate every year. So a lot of things carry over from year to year, and it has been consistently good for the last decade.

KWS also builds a lot of R6 Yamaha engines, says Spalding. “The R6 is very popular on the mini-sprint side as well. For motorcycle road racing it’s GSXR, R6 and a few CBR1000s.  We have a CBR on the dyno right now. Kawasaki’s 600 engines are popular but not the 1000s, the ZX6R is good for road racing. The engines are all inline-fours with overhead cam valvetrains.”

In the last two or three years in an effort to get the weight out and maximum power, all of the manufacturers have gone to titanium valves, which Spalding says are great and extremely light, but titanium doesn’t have the durability of the stainless valves and is very expensive to replace. “A set of Ti valves for a GSXR runs about $1,000. In the whole grand scheme of things, that’s not too bad for Ti valves. The stock valves are pretty good for what they are. You could go to stainless valve, and we do use them for nitrous applications because Ti doesn’t like the thermal shock of nitrous. They tend to start chipping off at 45 degree angles. The seats we use for stock Ti valves is a steel seat, but when we go to big aftermarket Ti valves we use a bronze seat. The problem with going to a stainless valve is they are so much heavier, and then you have to have a spring to control that valve. And then no one wants to rev any lower than what you can with a stainless valve. You can tell the guy it’s got a heavier valve in it so it lives, but you’re spraying it so it makes more power anyway.”

Most of the time we use an OEM Ti valve with a stellite coating on it, unfortunately, once you start to wear through the stellite at the 45 degree area, it will wear very quickly.

AC Moto out of Durham, NC is another dedicated sportbike engine builder and bike builder for road racing classes. AC Moto’s Ibrahim Yousef says that one of the issues he faces building engines for the superbike class is the limitations on engine modifications throughout most racing organizations (CCS, WERA, AMA) rules.  “As a builder we are not allowed to modify the bottom end,” explains Yousef. “All we are allowed to work with is the cylinder head, granted, this is not a problem the head is one of the main areas of the motor where you are going to gain the majority of your power. But we have to keep in mind we are still working with 998cc -1,000cc displacement motor with standard stroke and rods from the factory. We can only port so much without compromising the build. It would be pointless for us to go with a large port design when all we have to work with is 1,000cc bottom end.”

From road racing engines on their litre bikes, Yousef says most of his riders are looking for mid-range and top-end power. “Top-end power is needed for the straight-aways on the track and the mid-range power is to give the riders the kick they need to get out of the corners because the bike will not allow them to play with much of the throttle in the corner. This is why they have to focus more on their corner speed.  We produce mid-range power with a variety of cam profiles;  We’ve been very successful with Yoshimura cams on the ’07- ’08 Suzuki GSXR1000, which complements the CNC porting profiles we design. The GSXR1000 build is probably our most common build, as we have spent more R&D on the GSXR’s than other models. Yousef says there’s something to be said for longevity of the GSXR1000. “The bottom end has not been changed since 2001 other than compression, which comes from the piston design. This is not a problem when it comes to the initial build because we bump the compression up on the motor from the cylinder head.”

Yousef says the Supersport 600cc class is also very limited in that almost no engine modifications are allowed, but there are still things an engine builder can do to improve the stock engine. “The rules do not allow us to modify any aspect of the motor, only basic bolt-ons like a full system exhaust, air filter and, if I’m not mistaken, a fuel tuner. What we provide for this class is a motor with a minimum amount of compromises from the assembly line. All the bearings are color coded and have different oil clearances from the factory. We make sure that our racers are not going to receive an engine with incorrect oil clearances. We determine the oil clearances from the codes that are on the crankshaft, connecting rods and the crankcase. This allows us to determine the correct bearings for the rods and mains. I go inside all of the our engines to check oil clearances. Then I double check my clearances with Plasti-gauge and that’s about it on the bottom end. I check piston ring clearances to make sure that the engine will hold its specified compression. The cylinder head in most production 600cc motorcycles are shim-style under bucket design, so I make sure that those clearances are up to factory specs as well."

Yousef cautions that checking clearances is critical because they are not always correct from the factory. “These are high revving motors and we have to make sure the clearances are to spec or it will affect the performance of the engine.

Those are the main aspects I look over when building a Supersport or stock engine. We need to remember that racing conditions are much more extreme than road driven motorcycles. However, there are some guys out there I know are putting their street bikes through hell. I know I do.”
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Brendan Baker
For the better part of 30 years, Brendan Baker has been involved in the automotive aftermarket and racing industry in some capacity, including the last 11 years at Engine Builder magazine. Brendan’s aftermarket career started in high school working for an auto parts store in Akron, Ohio. He has worked many areas of the aftermarket from counterman to technician and earned his certification as a racing mechanic in 1989. He has worked for several racing schools and teams at various levels, including being an owner/driver of his own semi-professional racing team for several years. Brendan studied Journalism and Computer Science at Kent State University and lives in Akron, Ohio with his wife Lori and dog Kylie. In his free time he enjoys riding his motorcycle and racing go-karts.