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the Suzuki GS 500E
By David R. Johnson CRA #242
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
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
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
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.
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
Installing the Pingel Petcock
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.
CFM-Woodcraft rearsets are simple
and tough. The hardest part is
finding someone to add length to the stock shifter.
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.
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
Works shock for the GS500
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.
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:
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.
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.
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.
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),
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.
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?
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
Anoka, MN, but there are other good shops.
There are also lots of untrustworthy scuz-types in this business.
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).
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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.
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!
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.
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.
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.
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