Earlier, we discussed the four things that occur in a four-stroke engine. They are intake, compression, ignition, and exhaust. Since your engine does precious few other things, improving your engine's ability to scoot you down the road at an illegal pace mostly depends on improving the efficiency of these four processes.

EXHAUST

I want to start with the last one because it is the most common engine modification people typically employ. There are nearly no limits on exhaust systems available to the Star line. Myriad companies (BUB, Vance & Hines, Cobra, Jardine, DG Hard Krome, Samson, Roadhouse, Daytona, Raask, and SuperTrapp to name a few) make replacement systems for your Star. Different sets are available for different bikes, but someone covers nearly every style. Subtle differences amongst most systems are purely aesthetic. For instance, there is no significant performance difference between a turnout, slash-cut, straight, fishtail, or tapered end if all mounted on the same muffler. However, radical differences in the systems (like if they are 2 into1's, drag pipes or slip-ons) are quite significant.

The options start with simple and inexpensive sets called slip-ons. These are just replacement mufflers such as those available from Jardine and Cobra. They cost the least and are the easiest to install. They are typically louder than stock mufflers, but not offensively so to most ears. They typically yield the lowest power increases, although they can contribute to a freer revving engine.

There are semi-complete systems. These typically are a slip-on for one of the pipes and a complete replacement for the other. Cobra, Raask, and Jardine all make systems like this. Sound and performance depend on the type of system. A system with replacement mufflers will perform and sound pretty much the same as a set of slip-ons. One added benefit over stock is greatly reduced weight. A benefit these systems have over complete replacements is that they are less expensive. Expect to pay about $100 more for these then you would for slip-ons.

A system without mufflers, known as 'drag pipes', will be much, much louder than stock. If the engine is properly tuned, there can also be very significant power gains with these. They are inexpensive, popular, and easy to install… but don't expect to win that 'neighbor of the year' award if you live in a community that is less than biker-friendly. Too, drag pipes can get very annoying on long trips - especially if you have a windshield. The sound of drag pipes bouncing off a windshield can give you a headache in a hurry.

Then, there are complete replacement systems. BUB, Roadhouse, SuperTrapp, and Daytona make systems like this. These can do the most to radically alter the look, sound and feel of your bike. Most systems are renowned for a pleasing and deep rumble, snappy response, and dynamite looks. You get what you pay for, though. Systems like this can run several hundred dollars. Performance will usually be slightly less than is possible from drag pipes, but finish and sound quality are usually much better.

Of course, you also have the option of going the custom route. ISRA members have run the gamut all the way from drilling their bike's stock mufflers to welding complicated complete systems together. Results vary greatly, of course, from project to project.

Performance gains netted from changing exhaust systems are the result of improving the flow of exhaust gases along their merry way from your cylinders to the hole in the ozone layer. A common misconception is that increasing the flow of exhaust alone will improve engine performance. Increasing exhaust flow will result in a leaner mixture. Any change to your exhaust really should be accompanied by compensation to the intake system. You could actually do very serious damage to your engine if it is running too lean. At the very least, the pipes will probably turn unattractive shades of purple and blue. Assuming a properly tuned carburetor, the maximum high-end, high-rev performance ISRA members have been able to consistently achieve has been with drag pipes using anti-reversion baffles.

It is likely that you will experience higher performance gains with anti-reversion baffles than with no baffles at all. Your neighbors will probably like you more, too!

An example of this type of system would be Khrome Werks or Cobra Drags with a set of HP Plus baffles. Anti-reversion means that the baffle is specially designed to prevent 'backflow'. Imagine the exhaust gases leaving your pipes to be like a crowded subway turnstile. If people bunch up at the exit, fewer people can make it through. Exhaust gas is similar. Anti-reversion baffles reduce the 'bunching up'. If you put your hand behind your muffler (careful not to burn yourself!) and have someone blip the throttle, you can feel a real difference in exhaust systems. On a free-breathing system, you will feel the exhaust pulsing immediately - and strongly. The engine, having reduced the resistance in the system, will rev more quickly. It will also return to idle more quickly. These characteristics don't necessarily increase horsepower, but they decrease the amount of time it takes for your engine to get to the 'meaty' portion of the power curve. This makes your bike quicker and more responsive. On a stock system, exhaust pulses build up more gradually. There may be a few hiccoughs before exhaust gases are really flowing.

Aftermarket Exhaust + Throttle = putt putt putt PUTT PUTT PUTT

Stock Exhaust + Throttle = putt putt putt p… p… pu… put… Putt… PUTT PUTT PUTT.

Like I said, though, drags are good for high-end portions of the RPM band. If you are looking to maximize low-end grunt, you should probably be looking into a 2 into 1 collector system. There may be a loss of top-end power, but a system from Samson or Roadhouse may put more power where you actually want it. After all, you probably aren't spending all day screaming at 90 MPH. Systems like this also have the added benefit of producing a deeper, more acoustically pleasing rumble (of course this only my opinion - some love the 'bark' of unbaffled drags). 2 into 1 systems often claim to be tuned to make the flow of one exhaust pulse 'pull' the next out. Since the engine isn't working against itself, it can pull from lower RPMs. Aftermarket 2 into 1 + Throttle = BLUB BLUB BLUB. Even a smallish 650 sounds like a Chris Craft with a good 2 into 1 system. Just download the sound of Jeff Henon's exhaust from last month Daytona exhaust review for proof. A 2 into 1 system on a Roadie must sound like God's own bass guitar.

INTAKE

Let's look at the other end of the bike. Intake efficiency is dependent on a few factors. These are airflow (regulated by the air filters and a jet), fuel flow (regulated by a jet and a needle). Since intake is a combination of fuel and air, increasing intake efficiency means increasing the flow of fuel and air into your cylinders. The most common intake modification is a simple re-jet of the carburetors. It is rare that a re-jet is performed alone purely for performance gains. Re-jetting is about increasing the amount of fuel in the mixture. . This is typically performed to compensate for changes in the exhaust system. If you are looking to do more than merely compensate for exhaust modifications, you are going to need more than just more fuel. You need more air. More air PLUS more fuel = bigger BANG!

Methods for increasing the amount of fuel/air mixture in the cylinder can be characterized as either passive systems or active systems. Passive systems are much more common. One of the best passive systems on the market is the Big Air Kit (BAK) from Baron's, available for most Stars. It consists of replacement parts for your carburetor including jets, needles, air filters, and a crankcase breather. The BAK works by increasing the efficiency of flow intake. Intake occurs when the piston travels down the cylinder sucking in fuel/air mixture. In an engine equipped with a BAK, more fuel and air are drawn in to the cylinder compared to stock. Much like the effects of making exhaust freer breathing, a BAK will also make the engine rev more quickly and feel more responsive. That kind of a change can't be measured by a dyno.

If you are feeling more adventurous, you just may be able to out-achieve Baron's by noodling around with the carbs and air filters yourself. Our very own Mark Jelic has written up an excellent article providing step-by-step instructions. The highest 650 horsepower improvement over stock on the ISRA Forum to date was achieved using Mark's "Gonzo Air Kit" (GAK). Be warned, though: If you go this route, you give up Baron's excellent customer service. Perhaps the most important thing you get from Baron's when you buy a BAK is the technical support phone number. There are very few companies that so attentively hold their customer's hand (or the hand of the customer's mechanic) through an installation. That really should figure in to your decision if you feel you need support 'dialing in' the perfect set up.

Active intake systems actually force fuel/air mixture into the cylinder. These are superchargers and turbochargers. These are VERY pricey systems. Too, they are not available for most Stars. A Royal Star supercharger kit could cost you well over $4000. If you are willing to spend this much, you can probably afford to have a system either custom made or adapted to suit your bike. Superchargers consist of a compressor (driven by the engine) which impels more fuel/air mixture into the cylinder than would naturally be drawn in by the piston's downward motion. A good supercharger can increase power by well over 50%. Even doubling power (or darn near it) is not unheard of. Turbochargers are much the same, but the impeller is driven instead by exhaust gas. The brutally high temperature of exhaust gas, combined with the extremely high RPMs of the fan mean that a turbocharger's lifespan is a fraction of a supercharger's.

Between the line of active and passive intake systems are ram air systems. These are becoming very popular lately on sportbikes like the Yamaha R6. They work by pushing the fuel/air mixture along with the 'wind' generated by the bike's forward motion. A forward-facing scoop collects air to pressurize the mixture, forcing more into the cylinder than would naturally occur. The closest thing available for most Stars is the Kuryakyn Hypercharger. The Hypercharger is an active replacement for your air filter. It features a set of vacuum-operated butterflies that open more and more at higher RPMs allowing more air to be sucked in. Initial experience has shown that some Hypercharger-equipped Stars are quicker off the line than BAK/GAK equipped bikes. Performance trails off, though, as too much air enters the Hypercharger at higher speeds. I suspect that a jet kit which automatically self-adjusts the fuel mixture (like a 'Dial-A-Jet') installed with a Hypercharger will produce the more power than a BAK/GAK, although I am not aware that it has been successfully achieved yet. One thing IS for certain: Hyperchargers look WAY cool.

There are a few products which claim to increase power by mixing the air and fuel mixture, resulting in a more even ignition. They go by different names - Torque Master, Turbulator, etc. I have never heard someone say they don't work at all. Neither have I ever heard someone say they make drastic improvements. Perhaps they are worthwhile if you are looking for every last tenth of a horsepower possible for some sort of a dyno-topping contest at a rally. At any rate, they are not expensive - just expect to get about what you pay for.

One last note about achieving better intake/exhaust flow: You can have some of the internal parts of your engine polished. Some people believe that a chrome-like smoothness provides less resistance. It can be pricey, though. Gains to be had are pretty modest, too.

COMPRESSION/IGNITION

Compression occurs when the piston moves up the cylinder, pressurizing the fuel/air mixture. Ignition occurs when a spark ignites the compressed mixture. I have thrown these two events together, as they are both 'internal engine' operations. First, I want to specifically look at camshafts and pistons here. Performance camshafts are made with a different profile to slightly alter timing. While improving performance, it is usually at the cost of a lumpy, uneven idle. Lightweight pistons reduce the amount of work the crankshaft does on non-power strokes. Being lighter, they also are moved more readily by combustion. Sometimes there is a reliability tradeoff with them, though.

As far as products that improve the internal workings of the engine, the Harley-Davidson aftermarket can eat the entire metric market for lunch. When it comes to buying high-performance cams and pistons for your Star, you have very few options if any. There is one notable exception, though. Yamaha re-tunes engines from other bikes to suit the intended audience for each different bike. This is nowhere more apparent than in the Royal Star line. The Royal Star shares the engine of the mighty V Max. Yamaha re-tuned (de-tuned?) the V Max's ultra-powerful plant to provide a more, ahem, gentlemanly ride for the Royal Star. What does that mean? Two things. 1.) You can put back all the stock V Max stuff to achieve V Max ponies, and 2.) You can install V Max aftermarket goodies to surpass stock. Take a look at the list of modifications done to the engine of June's Star of the Month from Doug Blessing. With a little creativity, Doug has been able to achieve truly blistering performance from the once shy Royal. Even if you are on a more modest hot-rodding budget than Doug is, it is estimated that a carburetor kit, performance exhaust, and V Max cams will produce horses in the low 70s measured at the rear wheel. Pretty respectable in my book.

The Road Star's engine is entirely new, so we are going to have to depend on the aftermarket if we want performance cams and cylinders. I fully expect the aftermarket to embrace this bike with a fury. It has caused more of a stir in the motorcycle press than any other bike in recent memory. Though options are sparse now, I wouldn't bet on it to stay that way for long. If the short amount of time it took the industry to get Road Star exhaust on the market is any gauge, I'd say we should start seeing serious performance options available for the big Roadie as early as next summer. The other bikes in the Star line up share engines with previous Viragos. The 650 is a bored out version of the old 535 mill. The V Star 1100's plant is a re-tuned Virago 1100 motor. In theory, any performance equipment from either engine (stock or aftermarket) could be adapted to work on the V Stars. The Virago 1100's cams are a little hotter than the V Star version. Bottom end grunt is lost in the bargain, though. That means that if you are a short-shifter like I am, you may never notice the performance increase you achieved. The same holds true when comparing the 535 to the 650.

One might think that altering the actual power stroke would net the largest improvements to an engine's performance. The engine develops power during the power stroke, after all. There aren't too many options, though. Back in the dark ages (the 1970s, for instance), there were potential gains to be had from swapping out your old 'points' for an electronic ignition system. Well, it's the 90s now. If there are gains to be made in the ignition arena, they are small. Some say that Splitfire plugs will improve ignition. They were forced by the courts to admit they didn't, though. High-end spark plugs like Bosch Platinums are probably a worthy investment. Even if performance gains are minimal, they aren't too expensive and they last a long time.

There are those customizers, too, who proudly cry out "damn the torpedoes, full speed ahead"! These are the guys who remove or alter the rev-limiter on their bike. The rev-limiter kicks in to prevent an engine from damaging itself. Altering it, therefore, can be dicey. It is possible, though, to increase the top speed of your Star this way. Playing around with such dangerous stuff is best left to those with many years of experience under their belt. When it comes to rev-limiters, I know I trust the abilities of Yamaha's engineers - the guys who showed Ford how to make a Taurus into an SHO - more than I trust my own.

OTHER CONSIDERATIONS

Last month we discovered that the most sensible way to gauge a bike's ability to haul butt is to divide its weight by its horsepower - comparing how many pounds per pony, as it were. Weight is a factor that many very often overlook when hot-rodding their engine. Back in the glory days of the Bonneville Salt Flats racers, hot-rodders would show up with bikes stripped of all but the barest essentials. Every piece of metal that couldn't be removed entirely was perforated like Swiss cheese. This is where the naked look of the chopper was born. Don't underestimate how much quicker you can make your bike by shedding weight. For that matter, you may be surprised at how much quicker your bike is if a certain piece of cargo decides it's time to start using that health spa membership!

Another thing to remember: Do you remember from school Sir Isaac Newton's observation that "bodies in motion tend to stay in motion." Well, Isaac, why can't my bike just go faster and faster? The answer is simple. Wind resistance is always getting in the way of a good time. More than any single factor, wind resistance is usually what defines the top speed of a bike. If it is possible to decrease your bike's wind resistance; you could add a few more ticks to the top end of your speedo. Maybe a little bikini bullet fairing would look hot on your Custom.

Gearing can also be altered to take advantage of your engine's power. Options are few for Star owners, though. The V Max rear-end can be installed on a Royal Star to raise RPMs to points of the power band closer to the peak. While it doesn't actually increase the engine's power, it ends up feeling that way. To use a musical analogy, it's something like putting a capo on a guitar's neck. It doesn't change the notes you can play - it just makes them easier to get to. Other Stars will have to rely on the ingenuity of their owners. Some folks have hypothesized that a Virago's final drive could be used on the V Stars… maybe you'll be the first person who can brag on the ISRA Forum about achieving this feat.

LAW OF DIMINISHING RETURNS

Power doesn't come cheap. Sometimes it seems that the more you spend, the less you get. Look at this example: If you are hot-rodding a V Star 650, for under $300 US you can get a set of drag pipes with anti-reversion baffles and a do-it-yourself carb kit. This can increase horsepower by as much as 25%. Meanwhile, you could spend $1,000 or more and maybe only increase that figure to 30%. Spend $3,000 and you may get 32%. So including the bike itself, you could spend $10,000 on a performance project that is STILL much slower than a $7,000 YZF600R. What's more, your bike may be much less reliable in the bargain. This is why you should have a clear plan with rational expectations BEFORE you start fiddling about. At the end of the day, souping up your bike should be fun. Spend as much (or as little) as you think is fun. And remember - if you run into a problem there is probably someone on the ISRA Forum who can help you out of a jam!