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Racing the Suzuki GS 500E
(Models 1989 to present)

  By David R. Johnson CRA #242

Disclaimer
General Racing Mods
Installing the Pingel Petcock
Suspension & tires
Supersport Mods
Superbike Mods
Common Failures

Disclaimer

The following are just the opinions of one guy, who races GS 500’s with the CRA at Brained International Raceway (BIR), and has spent considerable time fiddling with them. For all you know, I am a big doofus, so don’t take any of this as the last word on GS 500 racing. The GS 500 has only changed cosmetically since its debut in 1989, so most of these modifications should work on any GS 500.  If they don’t work on yours, try not to act surprised.  This isn’t my day job, after all.  Oh…and do I need to mention that motorcycle racing can be dangerous?

 

A Cheap and Easy Way to Start Racing

The Suzuki GS 500 is an incredibly tough machine, despite the fact that these are considered entry-level bikes.  If they can survive a 5-hour endurance race at BIR, blasting down that speed-intensive front straight at 10,000 + RPM for a MILE out of each 3 mile lap, they will put up with any occasional thrashing you might give them.  Their mechanical simplicity and the fact that they have been virtually unchanged for a decade means repairs are relatively easy and parts are plentiful.  The Central Roadracing Association (http://www.cra-mn.org) in Minnesota probably has the most racing GS 500s in the USA because they have an Ultralight class where these critters thrive.   They show up in race trim all over the country, but are not generally competitive with machines like the 8-valve Kawasaki EX 500 unless the track is tight and technical.

 

General Racing Modifications

 

Belly Pan

Many roadracing organizations now require a catch pan to be mounted under the engine on GS 500 race bikes.  The Central Roadracing Association in Minnesota adopted this rule in 2001, and racers scrambled to comply.  Fortunately, Rich Omdahl of Ward Performance (952-403-6740) was able to fabricate pans modeled after the lower quarter of SV-650 racing plastic.   Most pans are too shallow and low in the back to actually do any good if a big leak develops.  The Ohmdahl pans are nice, light aluminum pieces that are fireproof, aerodynamic, and deep enough to work.  Like most pans, these are moderately ugly, but they do a great job and cost only around $90.  Contact Rich if you need a pan.  

The “Omdahl” belly pan is attached to a GS 500

 

Engine Guards

Engine guards made especially for the GS 500 are available from your Suzuki dealer for around $50.  They won’t make your bike faster, but they will prevent the ignition and clutch covers from being destroyed in a crash.  This translates to a huge savings in time, trouble and cash, especially when you are fixing your bike at the track.  Engine guards also minimize the risk of a big oil spill during a crash, making things safer for racers behind you.  Some racing organizations require these on the GS 500.  One word of advice: Don’t use the torque specification recommended in the factory service manual. The bolts in this kit will snap before they get that tight. The nuts supplied in the kit are of the locking type, so they only need to be snug against the frame.

 

Side and top views of Suzuki GS 500 engine guards

 

 

Engine guards installed. Note that they attach to the front and bottom engine mounts with relatively unattractive and ill-fitting bolts from the Suzuki kit

Safety Wiring

Engine guards installed. Note that they attach to the front and bottom engine mounts with relatively unattractive and ill-fitting bolts from the Suzuki kit

Safety Wiring

Various bolts and other items must be safety wired on the GS 500 before you can go racing. General guidelines for what must be wired on a race bike should be contained in your racing organization’s rulebook. The Central Roadracing Association site (http://www.cra-mn.org/Rules_New.html) is a good example.  There are also a number of sites with tips on wiring, one example being the MARRC Roadracing School Bike Prep Guide (http://marrc.nova.org/html_docs/rrs.bikeprep.html#wiring).  You will need some safety wire pliers, a spool of safety wire, and a mess of small drill bits (they break-you’ll see).  A cheap place to obtain these things is Harbor Freight Tools (http://www.harborfreight.com).

Safety wire pliers

 

How’s Your Petcock?

There are three good reasons to replace the fuel lines and petcock on the GS 500, whether you are racing or riding on the street.

  1. One reason to ditch the stock set-up is there just too much hardware between the tank and the carburetors in the stock set-up. There are two different fuel valves, a trio of fuel hoses, plus a vacuum line. There are more potential leaks here than a race bike needs.  Also, it is a real pain to deal with this nest of tubes if you are removing the tank often.  Keeping track of all those hoses and clamps, and trying to route them the ONE correct way can be aggravating. This problem is solved by using a "quick disconnect" coupling and a single fuel line between the tank and carburetors. The fitting snaps together quickly during installation and pops apart with the touch of a button, instantly stopping fuel flow. It also makes tank removal a cinch.  I use the version with a shut-off in each side for the GS, connected with 5/16" polyurethane fuel line.  These devices are available from Lockhart-Phillips (www.lockhartphillips.com).  They are actually made for laboratory duty, but if they can stand up to having chemical solvents run through them, they should handle a little unleaded.

                          

Diagram of the stock fuel system  The Lockhart-Phillips quick disconnect

                  

 

  1. If you are racing, there is a definite possibility that the stock fuel valve will not have sufficient flow for an extended full throttle run. It is unwise to have the engine starve for gas and start bucking and wheezing in the middle of a high-speed sweeper.  You could end up in the weeds!  Also, if the engine is running lean in some parts of the track due to restricted gas flow, it could get very hot and start melting pistons or warping the head.  This intermittent lean condition might go unnoticed by the rider.  It might not even show up in a dyno run, unless you ran it wide open for a minute or two like you do at the track.  Adequate gas flow has no disadvantages.

 

  1. The best reason to replace the petcock is safety.  There are two fuel valves on a GS 500.  One is the standard "on-prime-reserve" switch that regulates flow to the carburetors.  There is another valve mounted on the tank that controls flow out of the tank.  This valve can only be closed with a screwdriver, but before you can do that, you must remove the seat, side covers, and the two bolts that hold the tank on, then lift up slightly and reach under the tank with exactly the right screwdriver, and try to turn a little valve that is blocked by a hose fitting.  This system is a disaster waiting to happen.  If a hose comes loose or gets ripped off in a crash, nothing will prevent the entire tank from emptying onto the ground, unless you brought tools onto the racetrack with you.  Even then, would you want to be standing next to a red-hot bike that had just crashed and is gushing gasoline, trying to get the #$%*! valve closed before the whole mess explodes?  I think not.

Replacing both fuel valves with a single Pingel petcock (www.pingelonline.com) solves problems 2 & 3 by providing a better-flowing valve that can be turned off at the tank by anything with opposable thumbs.  These units are made from high quality brass and stainless steel components.  They are functional, beautiful, and they make the pit girls swoon (I assume).  There is no specific application for a GS 500, but Pingel will make up a valve to fit your needs.  I ended up with "a 3/8-inch 6290-A valve with a down nipple and no reserve, and an A1602-C adaptor plate".  Cost was around $75.  Installation was easy.

 

Installing the Pingel Petcock

 

The annoying stock fuel valve is easily evicted by removing two 10 mm bolts.

The Pingel petcock comes with all you see here.

The hole in the tank must be enlarged slightly to accommodate the new Pingel petcock.  Don’t enlarge past the edge of the gasket. It would be bad!!!

The finished installation looks nice, simplifies the fuel delivery system, and solves the flow and shut-off inadequacies of the stock system.

Rearsets

Raask rearsets, distributed by Novella (847-359-2666), are one of the two available rearsets for the GS 500.  They are rather quirky, difficult to install and quite fragile in a crash.  Still, they are hinged, lighter and much higher than the clunky stock pegs.  CFM Woodcraft also makes rearsets for the GS 500.  They are much more durable than the Raask, but they’re not hinged, so you do NOT want to be dragging them through corners.  The Woodcraft units also require you to lengthen the stock shift lever.  That means tracking down a welder and hoping you get it right the first time.  You won’t if you follow their instructions.  Woodcraft also fails to provide an attachment point for the brake lever return spring, which is annoying.  Obviously neither of these products is a perfect solution, but having them means you can lean the bike over much further.  When the stock pegs drag, there is a good chance they will dig in and lever the back tire right off the ground.  Shortly after that, you will be eating asphalt.  With rearsets installed, the first thing that drags is your pipe.  If that is happening, you need to hang off more, set your ride height up, or just turn with more sanity.    Expect to pay $200-$250 for rearset hardware from either maker.  Think about getting some spares too, unless you are planning to be the first racer to never crash.

Stock Footpeg and Shifter

Raask Rearsets

With rearsets you can grind your pipe like this

 

CFM-Woodcraft rearsets are simple and tough.  The hardest part is finding someone to add length to the stock shifter.

 

 

Suspension and Tires

Front Forks

Anyone thinking of racing needs to do SOMETHING about the front forks.  The easiest thing is to install Race Tech Gold Valve cartridge emulators.  These will run you about $120.  Use the race setting (4 turns out) on the emulator, and install with 15 W fork oil and Race Tech non-progressive springs ($90).  The Race Tech web site (www.racetech.com) will help you determine what spring rate is best.  Nothing will improve the handling of a GS 500 under race-like conditions more than fixing the squishy front suspension. 

 

Rear Shock

Many people leave the stock rear shock in place for racing, mostly because a racing quality replacement is $300-$500.  It is not as horrendous as the front suspension, but it is under-damped, which leads to pogo-sticking through the high-speed sweepers, and squatting in the tight turns.  Works (Works Performance Products, Inc. 818-701-1010) is the most common replacement shock, mainly because it is the least expensive ($270).  Works shocks are also rebuildable, and the folks there get the job done quickly for around $60.  Fox Shocks (408-365-9700) also makes a rebuildable shock for the GS, but you may have to grind some metal off the swingarm for clearance to make it work (I wonder if Fox knows this?).  There are more expensive shocks available too, but not many racers want to put a $1000 shock on a $999 bike.

       

Race Tech cartridge emulators                                 Works shock for the GS500

 

Tires

Race rubber is readily available for the GS 500, probably because it uses the same tires as Aprillia cup bikes.   On a racing GS, the front tire size is the same as stock (110-70-17).  For the rear, most racers I know use a 150-60-17 (stock is 130-70-17).  The fitment guide will tell you the rim is too narrow for this tire.  It is, but this does not result in bead failure, even under extreme racing conditions.  It does modify the profile enough so that it impossible to get all the way to the edge of the tire.  If you can’t live with that, you can have your wheel widened to 4 inches by Kosman Specialties (http://www.kosman.net) for about $375, but then you won’t be legal in Supersport class.  I once tried the other racing tire choice (Metzler 140-80-17) and hated it.  It is taller tire than stock and a non-radial.  The bike steered like a cow, flopped unpredictably into corners and felt very top heavy.  When I switched to the 150 radials, I almost drove off the inside of the track because it turned so easily.  Race rubber is available from Dunlop (D-207GP and D-208GP), Michelin (Pilot), Metzler (Rennsport), and Pirelli (Dragon Supercorsa) in sizes 110-70-17 and 150-60-17.  The Supercorsa and Rennsport are the exact same tire with different tread patterns.  This makes sense since Pirelli and Metzler are the same company.  Most people at BIR have historically run Michelins or Metzlers, depending on which manufacturers were offering contingency money.  The way contingency works is you use their tires, fill in the form during race registration, put their decals on your bike, and finish well in the race (usually fifth or higher), and you get certificates useable for your next tire purchase.  I have ridden the Michelin Pilots and Metzler ME Z3’s back to back, and could not feel any real difference.  I believe any big name race rubber will perform adequately, so go where the money is or just pick one randomly and see how you like it. 

In 2000, Michelin paid contingency money in the form of “Bib Bucks”.  These coupons can be redeemed for face value when purchasing Michelin racing tires.  In 2001, they did not pay anything for ultralight classes (which is where the GS 500 runs), but Metzler did.  Money talks.  Lots of folks switched to Metzler last year.  Michelin’s  “smiling tumor” corporate logo is also less appealing than Metzler’s bulbous blue elephant.

Brakes

There are several brake components that should be upgraded on the GS 500 if you are going racing.  The front brake calipers were changed in 1996, and the pads are not interchangeable with the older models.  Be sure to get the correct pads by specifying the correct model year and comparing the new pads with the your old ones.  Most people never touch the rear brake on the track, and there really are no worthwhile modifications for it.  Some people even bleed a little air into the rear brake line so they are less likely to lock it up if they touch it.  The following modifications refer to front brakes:

 

Pads

There are brake pads available for the GS 500 from EBC, Galfer, SBS, Ferodo, DP and probably others.  There are also lots of pad compounds to choose from.  The metallic HH type pad is meant for racing, but has the reputation of being hard on rotors, at least on a GS 500.  To further complicate the matter, EBC apparently has regular “compound 101” HH pads for use with EBC rotors, and special “compound 110” HH pads for racing with stock rotors.  The 110 compound HH pads have “G” in their part number.  OK, even I am confused.  An alternative to HH pads that I have been satisfied with is the green so-called “organic” pads from Galfer, available from Lockhart-Phillips (www.lockhartphillips.com).  They provide good feel and stopping power without immediately destroying the rotor, and they seem to last a reasonable amount of time.  I have never felt that pad compound made much of a difference in stopping power on the GS, but the softer, non-metalic pads definitely wear out faster.  Even regular street compound pads will work for sprint racing, but they won’t make it through an endurance race.  Any type of brake pad must be watched closely on a race bike.  If you let them wear down to metal, it will ruin your rotor and possibly your day when the brakes suddenly fail.  Most brake pads sell for $20 to $35 per set.  The beauty of it is, you only need 1 set for a GS.

EBC HH metallic pads for 1996 and later GS 500 (left) and Galfer Green pads for 1989-1995 GS 500 (right).  Note that the pads are different shapes and not interchangeable.  The ‘96 pads also fit one side of the SV 650.

 

Rotors

The stock stainless steel rotors are adequate for racing.  Racers don’t usually change them until they wear out.  When rotors do go bad, they usually warp rather suddenly, often in the middle of a race.  It is therefore good to have another one in your box of spares.  One trick racers use with certain rotors to reduce warping is to replace the wavy washers behind the snap rings with flat ones, or remove them all together.  This lets the rotor float more and stay cooler.  When your stock rotor does finally warp (it will), the EBC Pro-Lite rotor is a good replacement that is lighter and cheaper than the stock unit.  These are available from Hi-Side Racing (www.highsideracing.com) and most trackside tire vendors for about $175.  Be sure to ask for the race rotor with the blue center, and not the street rotor with the gold center.  The race rotors are cast iron.  When your EBC rotor warps (it will), the blade can be removed from the center and replaced for around $100.  There are some people who like the aftermarket cast iron rotors for their supposed greater heat dissipation and stopping power.  I had one on my GS, but had to switch to a stock stainless steel unit in the middle of a race day when the iron rotor warped.  Maybe it’s just my clumsy brake technique, but I didn’t notice a difference.  Also, your cast iron rotor will be a rusty brown rotor if the bike gets rained on while it is sitting still. 

 

On some stock brake rotors, the snap rings can be removed with a snap ring pliers

The wavy washer can be removed to give the disk more freedom to float.  NOTE:  If done incorrectly, the snap ring will be bent, and possibly fail to hold the disk in place.  WARNING! WARNING! WARNING!!!  I do not recommend that you do this modification.  The illustration is just information about what SOME HYPOTHETICAL PERSON might do.  If you botch this up, you might crash, burn and die.

 

The EBC Pro-Lite rotor is lighter and less expensive than a stock rotor from Suzuki.  Use the blue rotor for racing and the gold one for street.  The 5 hex head fasteners that mount the rotor are best removed using an electric or air impact wrench after soaking with lots of WD-40.  They are prone to rounding or breaking off when attacked by some Yahoo with a breaker bar.  I have seen such a Yahoo and the havoc wreaked upon said fasteners.  Not pretty.

 

Brake lines

The best way to improve brake feel is to install a braided steel or Kevlar brake line.  These expand less than their rubber brethren and thus reduce the squishy lever feel that is so terrifying when you are trying to haul a careening GS down from 120 mph.  Some people buy these lines because they look cool (brake line fashion???).  Whatever your reasons, there are many sources for brake line kits.  Hi-Side Racing (www.highsideracing.com) can get you a kit for the GS, and Lockhart-Phillips (www.lockhartphillips.com) has generic kits you assemble yourself.  They cost around $80 for a generic line.  If you choose braided steel, you might want a hose that is covered in plastic because the unshielded steel hose can act like a hacksaw on your bodywork.  You must also choose between stainless steel or aluminum banjo fittings.  The aluminum fittings usually are not D.O.T. legal, so (technically) they can’t be used on the street.  I have not discovered the advantages to using the weaker aluminum fittings, except you reduce weight by about 100 milligrams.  Maybe just skip breakfast instead. 

 

Supersport Modifications

The 500 engine is a relatively primitive design; an air-cooled two-valve/cylinder twin evolved from the older GS 450 and GS 425 mills. Stock rear wheel horsepower is about 37. This can be increased to the mid 40’s with easy modifications that are legal in supersport classes.

The 500 engine is a relatively primitive design; an air-cooled two-valve/cylinder twin evolved from the older GS 450 and GS 425 mills. Stock rear wheel horsepower is about 37. This can be increased to the mid 40’s with easy modifications that are legal in supersport classes.

 

Pipe + Jet Kit

The biggest performance problem with the GS 500 is that it doesn’t breathe. There are aftermarket racing pipes available from Yoshimura (http://www.yoshimura-rd.com), Hindle (http://www.hindle.com) and Vance & Hines (http://www.vanceandhines.com).  These run $350 to $400.  The experienced tuners who build and tune engines for BIR racers prefer the Yoshimura or Hindle.  According to them, the V & H is an older design that makes less power on the dyno than the larger-volume pipes.  The V & H is noisier than the others too.  If you change the pipe, you will need to install a jet kit.  Dynojet (http://www.dynojet.com) and Factory (http://www.factorypro.com) have kits for the GS 500.  I prefer the Factory kit because they don’t ask you to drill holes in your slides, and they use real Mikuni jets with legible, meaningful numbers.  The Dynojet kit contains their own style of jets that have some bizarre numbering scheme so you can’t look at them and figure out what the hell they are relative to a stock jet.  That’s great if you’re never going into the carburetor again, but if you want to do more carb tuning at some point, it will help if you are using the same numbers as everyone else.

 

                       

Yoshimura pipe installed                                                       Vance & Hines Pipe installed

Noise and Power

The loudest pipe always makes the most power, right?  Many people believe that for one reason or another (been to Sturgis lately?).  The truth is, the most power comes from the best flow into and out of the cylinders, which is not the same as the most noise.  Sometimes a little backpressure actually helps the flow, so installing that loud furnace-duct pipe may not ideal.  I recently had the opportunity to see this demonstrated in a dyno test of a GS 500 using a Yoshimura pipe and two different baffles.  Keep in mind this is the SAME pipe with only the baffle inside the can being changed.  One GS 500 race bike was used in back to back runs a few minutes apart comparing a loud “race” baffle to the quieter “Zyclone” street baffle.  This was done after the bike was jetted for best power on the race baffle, so the street version should have been at a slight disadvantage.  To everyone’s surprise, the street baffle made more power between 5500 to 9000 RPM and made the same peak horsepower as the race baffle, even though the air/fuel mixture had been optimized for the other pipe.  So…do you want people to hear you when they go by, or see you when you (quietly) pass them?

 

Cylinder Head

There is nothing like a fresh valve job to make a 4-stroke happy. You can’t make power if your valves are leaky and gummed-up or if crud is leaking past the valve seals and polluting the mixture.  The GS 500 head is cheap to do, and lots of neighborhood and national machine shops specialize in motorcycle valve work.  I recommend against taking a motorcycle head to an automotive machine shop.  I like Bill Bune Enterprises (www.billbune.com) in Anoka, MN, but there are other good shops.  There are also lots of untrustworthy scuz-types in this business.  Beware.

 

Degree the Cams

Degreeing the cams means adjusting cam position relative to the position of the crankshaft and pistons.  This operation changes the timing of valve opening and closing events, and allows you to optimize horsepower output and shift the powerband to fit your needs.  In a race engine, low end grunt might be sacrificed in order to maximize horsepower near the top of the RPM range.   In a stock GS 500 motor, cam timing is not adjustable because the sprockets on each cam are held in place by two bolts and a locating pin.  This is easily fixed by removing the locating pin and having a machine shop cut slots into your cam sprockets to make them adjustable.  The entire degreeing process is a little too complicated to explain here, but you need a degree wheel, a pointer, a dial indicator, a piston stop (to find top-dead-center) and some numbers you want to use for cam timing.  Aftermarket cams will always come with a specification sheet that gives the ideal timing numbers.  The stock cams can be degreed for more top end power, but no one agrees on what these *secret* timing numbers are.  The stock numbers are shown below.  Once the apparatus is in place, valve lift is measured by a dial indicator as the crankshaft is turned to a specified number of degrees from top dead center.  If the readings are acceptable for valve opening and closing times, the intake cam sprocket bolts are tightened, the dial indicator is moved to the exhaust side, the crank is rotated to the next value, and the process is repeated.   Sounds simple, doesn’t it?  In reality, it is a long, rather frustrating process fraught with swear words and mutterings of “close enough”.  If you have never done this, there are cam degreeing kits complete with instructive video tapes available from Lockhart- Phillips (http://www.lockhartphillipsusa.com) and other sources.   If you don’t want to try this yourself, you could pay a race shop to do it, maybe for about the same cost as the video and kit ($250). 

Degree wheel mounted on crankshaft 

Engine with dial indicator on exhaust valve

  Cam timing specifications for stock GS 500

Advance the Ignition

Some folks like to change their timing with an aftermarket ignition advancer, which is really just a new rotor with the locating pin in a different spot.  Technically, this is not legal in Supersport class.  You can legally achieve the same thing by grinding slots in the mounting holes for the ignition plate, and moving the plate relative to the rotor.  A couple of degrees is as far as you want to go.  This alone can be worth one or more hp near redline.

 

 

Bodywork

There isn’t much bodywork on a GS 500, but the tail section can be replaced with an aftermarket piece to save a few grams and achieve that racerboy look.  Airtech (http://www.airtech-streamlining.com) is one of the few U.S. companies that makes a tail section for the GS.  It costs somewhere around $200 and comes unpainted.  The front number plate can also be considered bodywork.  Many people attempt to angle the flat plates to provide some aerodynamic advantage, while others use a curved plate.  Either way, a little aerodynamic slipperiness goes a long way on a 40-some horsepower bike.   

 

                                                                                                                                     Airtech tail section                                           Front number plate

 

Change the Gearing

Aftermarket front and rear sprockets are available, so you can get the gear ratio you need for your conditions.  Stock is a 16-tooth front and 39-tooth rear.  Evil Pumpkin Racing has a nifty spreadsheet that tells you what gearing the various sprocket combinations give you (http://www.evilpumpkinracing.com/gearing.xls).  Sprockets for the GS 500 and all manner of other hard to find racing bits can be obtained from Hi-Side Racing (www.hisideracing.com).  Terry Embury from Hi-Side is a racer who knows what works on race bikes and where to find deals on parts.

Rear Sprockets

 

Superbike Modifications

Supersport rules don’t allow you do much in the way of engine modification.  For superbike and higher classes, there aren’t as many restrictions.  Some things are simple, but if you need that extra final horsepower, you can spend cubic money for the last little bit.  Some people claim to get 55 to 60 horsepower, but it costs approximately a Subaru.

 

Air Filters

Replacing the airbox with individual K & N air filters is a simple way to let more air into the motor (http://www.knpowersports.com).  These filters are permanent replacements for the stock paper filter, and can be washed (with special K & N goo) and re-oiled (with other special K & N goo) indefinitely.  There are versions that go inside the stock airbox and versions that replace the airbox with one double filter or two single filters.

    

K & N double airfilter and maintenance chemicals compared to restrictive stock filter and Byzantine airbox

 

Machine work

Bill Bune enterprises (www.billbune.com) or some other fine machine shop can port the head and mill it to raise compression.  Milling somewhere beyond 50 thousandths will require cutting valve reliefs into the pistons.  You may need to use race gas after this.  You should also degree the cams after a substantial milling, because the cam timing will be retarded when you shorten the distance between the crank and cam sprockets.  A few racers (those with extra money) machine the head for bigger valves.  Some racers are going to 1mm overbore in the quest for power.  This is nonsense because it sacrifices any chance for a rebuild if the cylinders get scored in the next blow-up, and it adds very little power.  Do the math on the tiny fraction that the total displacement is changed and multiply by the 40-some horsepower you already had, and you come up with less than 1 hp.  It’s not worth it.  There are stories of a 555 cc modification that consists of GSXR pistons and sleeves, and a modified GSXR cylinder head, or some such thing.  No one sells this as a kit, so you would have to know what parts to buy and figure out what to do about carburetors, cables, gaskets, and a host of other things.  If you are going to that much trouble, maybe you should just get an SV-650.

    

Milled head with reworked combustion chambers and enlarged ports

 

Cams

Racing cams from mild to wild and valve spring kits are available from Megacycle Cams (415-472-3195).  Most of these cams require machining pistons for clearance and upgrading the rest of the valve train.

 

Remove the Counterbalancer

You can remove the counterbalancer, then send the whole engine bottom end to Falicon (http://www.faliconcranks.com) to get it rebalanced.  The oil holes in the bearing area also need to be plugged if you do this.  Theoretically, this reduces rotating mass and lets the engine spin up more quickly.  If you just remove the balancer without rebalancing (people do), the engine will shake hard enough to break the engine mounts off the frame. This is bad, especially if you are racing at the time.

 

Remove the counterbalancer?  I wonder if it’s in there for a reason?

 

The GS 500 Racebike Shopping List

 

What does it take to turn a street-going GS 500 into a racer?  The process differs, depending on your goals, needs, wants, capabilities and bank account.  The stuff described below represents a medium-sized approach to building a competitive Supersport racer.  This list does not include things like administrative obligations (race licenses, entry fees, and club dues), expendables (fuel, oil, and skin grafts) or associated costs (safety gear, tools you may need, a trailer, a new towing vehicle, etc).  Hey, racing is expensive, but you can skip everything except the tires and rearstand if you can bum a ride to the track.  Hell, skip the rearstand and lean the bike on a tree.  Of course, you will look like a dweeb.

 

 

 

Air Tech Tail Section

$212

Braided Steel Brake Lines

$90

Front Fork Accordions

$10

EBC Front Brake Rotor

$140

EBC HH Brake Pads

$30

Fork Accordions

$10

Front Stand

$120

Factory Jet Kit

$71

Grips for Clipons

$15

Michelin Pilot Race Tire - Front

$110

Michelin Pilot Race Tire - Back

$140

Novella-Raask Rearsets

$216

Number Plates and Stickers

$20

Pingel Petcock

$68

Race Tech Fork Springs

$80

Race Tech Emulators

$120

Rear Stand (since you no longer have a side stand)

$100

Sprockets – Rear (4 different sizes for gear changes, 4 X $40)

$160

Suzuki Engine Case Guards

$50

Vortex Clipons

$139

Works Rear Shock

$269

Yoshimura Race Exhaust

$285

Hours and Hours of Dangerous Fun……………..Priceless

 

Total

$2,455

 

 

Common Failures

 

Racing is hard on stuff.  No matter how durable a machine is, some parts and systems are weaker than others.  The best way to find the weaknesses in a bike is to pound the snot out of it until something breaks (i.e. racing). 

 

 

Counterbalancer Shaft Bearings 

 

These things wear out after one to three seasons of racing, depending on how much you run and how persnickity you are about oil.  You have to split the cases to get at these, so you might want to replace them during the off-season BEFORE the blow-up.  Markings on the engine case determine which bearings should be used.  Note that bearing sizes differ between individual engines.  The service manual tells you how to select the correct bearings for your engine.  It would be unwise to guess that all your bearings are the usual size or even the same size. 

 

     

 

Bearings are sold in halfs, as if you would ever replace half a bearing.  Order 2. Bearings are slipped into the inverted case.  Be clean, clean clean!                       Bearings go into the case, then the balancer goes in.  

 

 

Ignition Rotor 

 

Under high RPM usage, the bolt that secures the ignition rotor can back out.  The rotor will start to go eccentric and actually contact the ignition pick-ups.  This will short out and cook the ignition (my whole ignition melted, made a hole in the cover and ran onto the ground like mercury).  The bike will stop suddenly when your rotor reaches escape velocity and the bolt breaks off in the crankshaft.  You can prevent this with 0.004 cents worth of thread lock on the bolt. 

 

 

 

Case Guards

 

The Suzuki case guards described elsewhere in this page are indispensable for racing a GS.  It is strange that such a simple object would be prone to failure, but they are.  What is perplexing about them is they can take incredible amounts of abuse (like having a motorcycle slide on them at racing speeds) and still protect the engine.  Other times they just spontaneously break due to frame flex and/or engine torque.  These guards attach to the engine mounting bolts, where there is sometimes enough torsion in the frame to snap the mounting ears off.  This condition is hard to detect because it usually occurs on the lower mount, which is obscured by the mounting hardware.  Sometimes the only symptom is a buzzing engine vibration that goes away when you grab the case guard.  It is important to check these things, since a broken case guard would certainly fold up in a crash, and might allow the engine mounting bolt to loosen during a race.  It is probably a good idea to loosen the lower mounting bolt periodically, check behind it, and retighten it.  This will also ensure the bolt is not getting loose from all the vibration it sees.                                                  

Case Guards

 

The Suzuki case guards described elsewhere in this page are indispensable for racing a GS.  It is strange that such a simple object would be prone to failure, but they are.  What is perplexing about them is they can take incredible amounts of abuse (like having a motorcycle slide on them at racing speeds) and still protect the engine.  Other times they just spontaneously break due to frame flex and/or engine torque.  These guards attach to the engine mounting bolts, where there is sometimes enough torsion in the frame to snap the mounting ears off.  This condition is hard to detect because it usually occurs on the lower mount, which is obscured by the mounting hardware.  Sometimes the only symptom is a buzzing engine vibration that goes away when you grab the case guard.  It is important to check these things, since a broken case guard would certainly fold up in a crash, and might allow the engine mounting bolt to loosen during a race.  It is probably a good idea to loosen the lower mounting bolt periodically, check behind it, and retighten it.  This will also ensure the bolt is not getting loose from all the vibration it sees.                                                  

 

Damage inflicted on a case guard by a crash and slide.  Still functional! 

Spontaneous breakage of an otherwise pristine case guard 

 Close-up of a case guard fracture that was invisible on the bike

 

Spark Plug Wires 

 

The spark plug wires connect to the coil by pushing onto a pin in the coil housing.  After lots of vibration and excited electrons blasting through them, the ends of the wires get fatigued or toasted and the all-important sparking quits.  This first becomes noticeable under load at high RPM only, so it is hard to diagnose in the driveway.  It might be prevented by removing and snipping the end of the wire to keep it fresh, but eventually your wires will get too short!

 

Head Gasket

These engines will often leak oil from the head gasket after a certain amount of tormenting.  Once it leaks, the only cure is replacing it.  Tightening the head bolts or slathering goop on the outside does nothing but waste time.  Take that sucker apart and be done with it.  A head gasket costs about $15 and can be installed in a couple hours of puttering and swearing.  You should also replace the oil o-rings at this time.  Make sure you put the engine at top-dead-center and note the position of the cams before disassembly, or there will be crunchy noises when you try to start it.  Also, be sure side marked “up” is up.

 

GS 500 head gaskets come painted with special sealing material.  Don’t screw it up by scratching it off or adding your own goop.  These things leak just fine WITHOUT your help.

 

Camshafts

The cams and their bearing surfaces on the cylinder head are frequent wear points in these engines, especially on the exhaust side.  This seems to be a function of oil level, oil quality, severity of use, and luck.  The bearing surfaces on the cams often show some scoring if the engine has been raced much.  If you catch it early, the cams can be replaced before things get out of hand for about $110 each.  If the process goes too far, the cams get destroyed and take the cam caps and cylinder head with them.  By the time it makes a discernable noise the entire head is junk, so cam bearings should be inspected after every few races and cams should be replaced if they are getting scored.  And change the dang oil once in a while. 

 

The ends of the cams (the round bearing surfaces), the cam caps, and the cam bearing area in the head can wear out very quickly and expensively if lubrication is inadequate or use is severe.

 

Fork Brace

That metal plate between your forks does more than hold your front fender on.  This somewhat flimsy piece of metal is your fork brace.  It holds the forks rigid against all those cornering forces that would like to splay them out like a wishbone.  If you crash, the mounting holes get stretched or ripped out, but the bolts usually stay put.  You might not notice this damage when you inspect the bike because the bolts are still there, but you will certainly learn about it in the next corner.  The other common problem in this area is that the 4 bolts attaching the brace to the fork often loosen and eject themselves.  The result is the same as when the brace is broken; you go down in a corner wondering what made the bike throw you off.  You will also annoy the guy behind you when the bolt goes through his radiator at 120 mph.  The fix is easy: Inspect the brace after a crash, and use thread lock, safety wire or duct tape to secure the bolts.

 

Typical damage on a GS 500 fork brace 

 Close-up of crash-damaged fork brace

 


In case you think David isn't a *real* racer I have video proof.  Take a look at him  outbreaking and passing a SV650 at BIR.  See it HERE

 

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Last modified: March 15, 2006