Benefits From Increasing the Compression Ratio

Increasing the compression ratio is one component of many that will increase a SUZUKI GS / EFE’s HP. An increase in an engine’s compression ratio will provide more power for less fuel and add some snap when the throttle is opened.

Raising the compression ratio gives the greatest benefits with initial increases. This means that more HP is produced by the first point increase of the compression ratio as compared to the next point of increasing the compression ratio. To illustrate this lets use a stock 1985 (USA model) GS1150 (EFE) as an example. The stock compression ratio is 9:7.1 if you increase the compression ratio to 10:7.1 there might be a 4 or 5 percent increase in HP. Further increasing the compression ratio to 11:7 might only provide a 2 or 2.5 percent increase.

The reason for the a smaller percentage in the increase in HP with a further increase in the compression ratio is due to the aspect of the GS / EFE cylinder being like an lung, increasing its volumetric effiecieny basically means the lung is filling with more air and is breathing out more through the exhaust. It is not enough to just increase intake or exhaust. Both must be made more efficient.

GS / EFE 1150 stock cams open and close the engine’s valves with little or no overlap. This prevents emissions from escaping, but it also limits an engine’s breathing efficiency.

In conclusion a moderate increase in compression will use less fuel to produce more power and the extra cylinder pressure and heat generated will increase the gasoline’s burning efficiency. But if you really want to maximize the advantage of increasing a engines compression ratio this use of a Hi-performance camshaft is required.

Air density, a secret tuning factor

Air density is a computation mainly dependent on the temperature, barometric pressure, and the humidity of a volume of air.

Temperature in the USA is generally measured in degrees Fahrenheit, barometric pressure in inches of Mercury (inHg), and humidity in percent of Relative Humidity.

You can relate to how these factors effect the density of the atmosphere by using a balloon to simulate the earth’s atmosphere. When a balloon is filled with air and placed into a refrigerator it begins to shrink, this is due to the drop in temperature of the air inside the balloon. As the air cools it releases energy and slows down,because the air molecules are not bouncing off each other as much, they remain closer together and more of them will now fit in a smaller area. The opposite will occur if the balloon is heated.

The effect of humidity is a little more complicated. A change of humidity in the atmosphere is caused by a change in the amount of water vapor mixed in with the common gases already present in the air. As more water vapor is put into the air is displaces these gases. The water vapor is also less dense (weights less) than the gases in the air. When we take air that is at a set temperature and pressure and start introducing increased amounts of humidity we begin to cause the overall density of the air to decrease. Therefore, the density of the air is the greatest when there is no humidity.

Changes in temperature, pressure, and humidity can have different amounts of effect on the associated change in air density. A change in temperature or pressure causes a proportional change in density. In other words, a 1% change in temperature causes a 1% change in density. Again, the effect of humidity is more complicated, because the effect of humidity on density is also dependent on the temperature. A 50% increase of humidity when the air temperature is 70f degrees may cause a 1% decrease in total air density, but a 50% increase of humidify when the air temperature is 90f degrees may cause a 2% decrease in total air density. This effect is due to the fact that it takes lot more water to cause 50% relative humidity at a 90 degree temperature than it does at 70f degrees. The humidity must also be considered in that it makes up some of the density of the air, but it has no value being there.

The air in the earth’s atmosphere is made of various gases and water vapor. Neglecting the effect of pollution there normally is 20.9% of oxygen, 75% of Nitrogen, Carbon and very small amounts of some other gases. Oxygen is the most important gas in the atmosphere as far as an internal combustion engine is concerned. This is due to the fact that the oxygen is used to burn the fuel placed in the chambers of the engine. When more oxygen can be placed in the chamber it allows one to also place more fuel along with it and therefore create more power. The air density relates to this because when the air density increases the amount of the combined gases and water now fit into a smaller area, this includes oxygen. If the air is denser than there is more of it therefore more amount of oxygen will be taken into the engine.

The term commonly heard among racers is “density altitude”. Density altitude is the density expressed if feet instead of grams per cubic centimeter. It’s a lot easier to relate a change of density in a couple hundred feet rather than a change of 2.534 g/cm^3. The use of density altitude is taken from the U.S. standard atmosphere table. This table relates the density of an average day at sea level (59 degrees, 29.92 inHg) and how it changes at different elevations in the atmosphere. As one climbs in altitude the density falls off at a predetermined exponential rate.

In conclusion I highly recommend either an Air Density Gauge or a Altimeter as tools to be used for adjusting your Fuel Curve and Ignition Timing. I firmly believe that these items are essential for tuning at the Race Track

All you wanted to know about GSX tuning but were afraid to ask

Speedy Steve Racer was one of the original sites GSX engine tuning gurus. Steve produced a complete guide to GSX engine tuning and we will republish it here through the vault.

Here is Steve’s original introduction.

Steve racer

HELLO RACE M8’s,The objective of this thread is to create a information baseline for all of the OSS members who are currently or who are planning to race ‘AIRCOOLED SUZUKI’S’ in Santioned Motorcycle Racing Events throughout the world.

Currently we have a number of OSS Members who in the past or present have won racing Championships competing with their ‘Old Skool Suzuki’s’. The wealth of knowledge and experience from these individuals can help other OSS Members who have desire not only to WIN Races but Championships also.

Presently OSS Members have won National & World Championships
in ‘Road Racing’, ‘Sprinting’ and ‘Drag Racing’, and with the help and informational input from these successful racers there is no reason that in the near future when a competitor see’s an bike with an ‘OSS STICKER’ they will consider that Sticker as a “SECRET WEAPON”.

I am looking forward to your feedback in order for this Hardcore Race Thread to begin. So DnD, AT_, LUKE, PETE 750ET, H_ippy, Gary 1371, BBK and the rest of my OSS RACE M8’s and Members, let’s get this thread going.

CHEERS

SSR

I Shut Them Down, Then Shut Them UP

 

Oldskool Oldskool, the road less travelled

614982_10151073061812733_377962059_oJohn Oliver (AKA Yoshi-Johnny, AKA YJ) is a long time OSS member and Pops Yoshimura enthusiast. John is a professional bike mechanic and many will remember his iconic take on the classic Wes Cooley GS 1000. Ten years ago, when John first rolled up at an OSS gathering on his GS, for me and many others,  at the time, his bike fully embodied the true  spirit of OSS. An air-cooled 8 valve GS1000 engine and classic Wes Cooley paint job but running on modern 17″ wheels,  sporting a mono shock conversion  and a set of gold anodised upside down GSXR forks. Evolution of the species. John’s love for Suzuki’s 8 valved air-cooled GS1000 engine has never faded. We asked John to tell us a little about his dream engine build and here is what he told us.

KM

Oldskool Oldskool, the road less travelled. John Oliver

It’s always been a dream to own a full blown Yoshimura motor but I don’t earn enough to just go out and buy one so I am gonna have to do it the only way I know how, a p.p.p.piece from here and a p.p.p.p.iece from there. So, I am in the process of getting together for the race bike I am going to prep for myself to go racing instead of others!

Engine

Yoshi motorI got hold of an old NCK drag motor a few years ago and it has a pretty good crank and gearbox in it. Crank has Katana rods and along with being welded it has straight cut primary drive gear, along with a matched one for the clutch basket. Cases have been lightened and dipped at Ribble Technologies in Preston. So the bottom end is as good as my budget will allow for the moment. I do need a new clutch before it turns a wheel in anger and this will involve having the straight cut fitted.  Originally the NCK engine was a 1420 drag engine but on the road or track that sort of capacity would generate too much heat and quickly cook itself.

yoshi pistonsGraeme Crosby in conversation said he preferred the power and reliability of the 998cc motor as it gave enough power and was reliable, Pops and he discovered the bigger the capacity went up, the less reliable and problematic it all became. Craig Smith, my good mate in Australia who has been on here for years is a major inspiration for the build as his black “skunk” race bike is still one of the outstanding bikes on the site. He raced it to good effect in NZ and didn’t suffer with reliability issues. He went bigger and bust his crank!His motor punted out 135 rwhp and that is my aim with this… I won’t be gutted if it doesn’t get there, but it would be nice if it’s something like.

So the pistons are custom made 1100cc Wisecos and are one of only 3 sets made this particular profile I think. All the gaskets and seals will be replaced with standard (where necessary) or Cometic (where it’s ok to cheat!) and special ones (base and head).

Head

bladeThe cam chain was a weak spot on Yoshimuras race engines and the team did all sorts to try and reduce the extreme wear during races, extra jockey wheels, longer cam chain, shorter tensioner blade, POLISHED cam chain links and manual tensioner were all employed in the hunt for reliability. Most of this development actually went into the first GSXR engine. So all the above mods will be done to this engine.I have had a jockey wheel and plate made but Roger Upperton does a better version which is more like the GSXR version than the one I have. The extra jockey wheel at the back of tthe head is the reason the tensioner blade is shortened.

 

Yoshi headThe head has been checked over and overhauled from scratch. Bigger valves, seats cut to match and a tidy port job will make the gas go in quick and hopefully make it work right.

camsValvesCams are very lumpy custom profile ones from New Zealand and require cut aways for them to turn in the head! Shims will be under bucket care of Kibblewhite, buckets, retainers (titanium) and collars. Dialled in cams will be easier with Rogers version of the jockey wheel than the Smithy version. I may put a twin plug set up in as well when I actually get to the build

Carbs
Carbs will be Mikuni VM33s and are getting quite scarce, these are about as big as you should be going on a bored out GS1000 engine, anything bigger just makes them bog down when you crack the throttle open.

Jockey wheel

 

 

 

Ignition
Ignition will be taken care of by Boyer Brandsen mini digital set up until I get a self generating system organized…

Speed is all a question of money…I wanna go fast but my wallet says whoaaah.

YJ

Discuss here

Bandit Coil Spring Conversion

Words & pics: Lee Workman

Bandit clutch conversionBandit Clutch

The clutch assembly fitted to all Bandit 1157 motors is, frankly, shite.

Based on the same principle as the GSX-R Slingshot unit, it’s diaphragm-sprung with ten driven plates and ten drive plates of 225mm diameter (the GSX-R’s are 230mm diameter which doesn’t sound much, but offers a huge increase in surface area for friction) and has a cheap cast alloy basket with a steel reinforcement strap fitted in an effort to stop it flying apart (as opposed to the large all-steel basket used in the GSX-R).

Under normal circumstances this unit is fine but, as soon as you start giving it a reasonable amount of abuse or tune the engine, it will struggle to cope with the extra demand and eventually slip. Heavy-duty diaphragm springs are available and will slightly improve matters at the cost of a heavy clutch lever, but the whole unit is better off in the bin. Trust me …

To convert your Bandit 12 clutch you’ll need the following parts from Suzuki,

No. Description Suzuki Part Number

Qty

Price � (ea.) Source Model

1

Clutch inner hub

21410-06B02

1

49.46 GSXR1100 G,H & J

2

Pressure disc

21462-06B00

1

23.49 GSXR1100 G,H & J

3

Coil springs

09440-20013

4

1.31 GSXR1100 G,H & J

4

Spring spacers

09180-06174

4

1.72 GSXR1100 G,H & J

5

Washers

09160-06020

4

0.53 GSXR1100 G,H & J

6

Bolts

01107-06307

4

0.71 GSXR1100 G,H & J

7

Drive plate (Fibre)

21441-48B00

11

9.53 All GSXR 1100’s

8

Driven plate (Steel)

21451-48B00

10

5.47 All GSXR 1100’s

9

Clutch Basket

21200-40814

1

176.53 GSXR1100 K,L,M & N

 

Yep, you’ll need to replace that crappy clutch basket, they are expensive new, but you could get one from B12 Clutch 1a breaker, you can use one out of any Slingshot model. Beware – they look identical to the earlier Slabside one, but the 1052cc motor has different gearing on the crank. The primary driven gear at the back of the clutch basket of Slabside engine has 73 teeth. The bandit primary driven gear (being essentially a 1mm over bored 1127 motor) has 72 teeth – the same as a slingshot one.
Follow the previous instructions for the GSXR’s then, once the inner hub is completely off, remove the outer basket also.
Pull the basket partially out, then push it back in again, this will expose the needle roller bearing and the spacer, remove these from the shaft then remove the clutch basket and alternator/oil pump drive gears careful remove alternator oil pump gear from the b12 basket and fit it into the slingshot basket
If its still stuck to your clutch basket, you will need to (carefully) remove this bandit drive gear, and fit it to the GSXR basket.
They are totally different; the alternator/oil pump drive gear off a GSXR has different pitch teeth and will foul your bandit alternator driven gear and your oil pump driven gear.

Once you’ve done this you can fit the new GSXR Basket using the original thrust washers in their original places.
Ensure the alternator an oil pump drive gears are engaged with the driven gear behind the basket
When positioning the basket on the counter shaft and sliding it ‘home’ – take extreme care to line up the alternator/oil pump drive gears with the alternator and oil pump driven gears, if they are not fully engaged, and you tighten the hub nut, it WILL snap, and they cost around £80!

Fit the new coil spring hub assy just like the GSXR procedure with one exception, –
The counter shaft of the bandit engine is again longer than the Slabside one, but it’s different to the Slingshot counter shaft, the dimensions for the bandit spacer are 35mm O.D, 25.5mm I.D and 6mm thick. Also as the original bandit hub has a different thickness base to either of the gixxers, it still works out that you need a 10mm ball bearing to take up the slack between your original bandit pushrod, and your push piece.
Again secure the hub using your original nut & washer on the new spacer fit the new GSXR clutch plates and pressure disc assy as above.
And you too have a GSXR spec, coil spring clutch!, Again you can go and fit a lock up straight on if you wished!, Or leave it as it is and go and do stoopid stuff, safe in the knowledge that you’re clutch can take it!
Now, extra hints and tips.
Tip 1: When you do the job, put the bike on its side stand and carefully lift the front wheel and chock it on a brick – this will stop you losing any oil when you remove the clutch cover.
Tip 2: When buying new clutch plates, use only genuine Suzuki parts – I know they’re more expensive, but it’s false economy to put cheapo plates in. I know, I’ve tried ALL the super-trick/heavy-duty ‘performance’ clutch plates and they just don’t compare with the genuine stuff. You have been warned!
Tip 3: With this particular conversion you fine-tune the biting point by changing the ball bearing – if it drags too much (assuming you’re using the correct grade oil and the steels aren’t warped), then you need more travel so try fitting an 11.5mm one instead. If it slips (assuming the fibre plates and/or the springs aren’t worn), you need less travel so pop in a 9mm one. It really does make a difference!

Also take the time to make the special tools, they’re a piece of piss to make, and really make life easier.

Special tool one: You’ll need two pieces of steel bar that are 200mm long, 25mm wide and 5mm thick (ish …), drill two 6mm holes in each bar with the centres 165mm apart then, at one end of each bar, fit a M6x30 bolt and secure it tightly with a nut on the underside. At the other end, open out the 6mm hole to 8mm and join the two bars together with a M8x70 bolt and loosely secure it with a nut on the underside. To use it, the M6 bolts will neatly fit into the slots on the diaphragm pressure disc and the M8 bolt will fit straight into the swingarm spindle – once the slack is taken up, you’ve got both hands free to undo/tighten the big 50mm holder nut!

Special tool two: First get one 400mm long piece of square section (20x20mm) bar and two old GSX-R clutch driven (steel) plates. Put the plates on top of one another and drill three holes equally around the diameter and secure them to the square bar using two M6x60 bolts and 20mm spacers and a couple of M6 nuts (this way, you can support the basket really well and reduce the chances off slipping, as the plates will be deep inside the unit). Finally put a small M6x10 bolt and nut through the remaining hole to secure the plates together. This is a wicked tool to have, when you’re trying to remove/secure the hub nut at 160Nm!

Anyway, in preparing this article I’ve been down to my local Suzuki dealer to get the correct part numbers for you to order and latest prices (all, are + v.a.t.,and correct at August 2002), and to ensure that those of you using second hand stuff from the breakers get the right bits off the right models. I’ve already checked to see which part numbers are superseded by later ones and that the information given is correct to the best of my knowledge and experience etc– aren’t I good to you lot, eh?

GSX-R Coil Spring Clutch Conversion

GSX-R COIL SPRING CLUTCH CONVERSIONS

Words & pics: Lee Workman

Before we start, I’m no journo, so you’ll have to forgive the lack of long and rambling intro and humorous asides throughout. I’m an engineer by trade and have been messing around with Suzuki’s big bore oil-cooled motors for ages and I’ve picked up a few tricks and developed a few of my own along the way.
I’ve done this coil-spring clutch conversion a few times on later GSX-R’s (and Bandit Twelve’s too). It’s cheap, very effective and it’s a piece of piss, so here are the facts.

There are the two types of clutch unit fitted to the GSX-R range and Suzuki’s first attempt, the coil spring type, is definitely the best. Fitted to all GSX-R Slabsides from 1986 through to 1988 (the 1052cc G/H/J models), it uses ten steel driven plates and eleven fibre drive plates and is clamped together with four coil springs acting on an alloy pressure disc.
With any clutch, the limiting factors are the unit’s overall strength, the surface area available and the clamp load on the drive and driven plates. The design of the Slabside coil-spring unit excels in all three areas – this unit can easily cope with even the most ham-fisted wheelie/burnout merchant and on the road it should handle over 160bhp as stock.

OLYMPUS DIGITAL CAMERA

For the heroes or for strip use, it can be still further improved with the use of heavy-duty coil springs, and for the serious drag racers out there, there are a couple of aftermarket ‘lock-up’ type conversions, which bolt straight in and replace the existing pressure disc. The lock-up is the ultimate in super-strong non-slip clutches.
Then there’s the diaphragm type. Fitted to all GSX-R Slingshots from 1989 through to 1991 (the 1127cc K/L/M/N models), it uses a similar clutch basket and the same driven and drive plates as the earlier Slabside clutch (with the exception that there are only ten drive plates in this unit), but the plates are clamped by two diaphragm springs acting on a different pressure disc design.
This unit is fairly robust and is less prone to ‘judder’ than the coil-spring type, but it starts to struggle with more than 140bhp and if you like your wheelies and burnouts or if you launch it hard on the strip, it’s not long before it gives up the ghost .

There is already a conversion kit on the market from APE, costing around £190, which converts a Slingshot diaphragm clutch to a coil-spring unit like that of the Slabbies and, therefore, allows the fitting of a ‘lock up ‘ kit at a latter date if necessary. But I’m going to tell you how to do it (using quality components) the cheap way. You can either get the stuff from breakers for around £30 or, using NEW genuine Suzuki parts for about £80 – about half the cost of the over-the-counter unit. And in a later article, I’m going to tell you how to fit one into your Bandit Twelve motor too, so keep any eye out for that, okay?

Anyway, in preparing this article I’ve been down to my local Suzuki dealer to get the correct part numbers for you to order and latest prices (all are plus VAT and correct in August 2002). And to ensure that those of you using second-hand stuff from the breaker’s get the right bits off the right models, I’ve already checked to see which part numbers are superseded by later ones, and that the information given is correct to the best of my knowledge and experience etc. Aren’t I good to you lot, eh?

Firstly for those of you starting with a Slingshot GSX-R 1127 (a K, L, M or N model), you’ll need the following parts:

 

No. Description Suzuki Part Number

Qty

Price � (ea.) Source Model

1

Clutch inner hub

21410-06B02

1

49.46 GSXR1100 G,H & J

2

Pressure disc

21462-06B00

1

23.49 GSXR1100 G,H & J

3

Coil springs

09440-20013

4

1.31 GSXR1100 G,H & J

4

Spring spacers

09180-06174

4

1.72 GSXR1100 G,H & J

5

Washers

09160-06020

4

0.53 GSXR1100 G,H & J

6

Bolts

01107-06307

4

0.71 GSXR1100 G,H & J

7

Drive plate (Fibre)

21441-48B00

1

9.53 All GSXR 1100’s

The parts needed for the conversion. What You'll Need

Then you’ll need two extra components – a 10mm steel ball bearing from your local bearing factors, and a hub nut spacer too. You’ll need to get one of these knocked up by someone with access to a lathe or any local engineering firm should make you one for around a fiver. The dimensions are 35mm OD and 25.5mm ID and it needs to be 10mm thick.

Got all them? Good, so here’s how you actually do it. Firstly, shift the transmission into first gear and remove the nine screws from the clutch cover. Then take off the clutch cover and remove the large circlip in the centre of the hub before you take out the pressure disc lifter and the push piece and its bearings. Hold the pressure disc from moving using the special tool no.1 (see below), undo the big holder nut and remove the diaphragm springs and the spring seat and then the pressure disc.
Remove the drive and driven plates, followed by the wave washer and its seat, then hold the hub with special tool no.2 (see below an’ all) and undo the hub nut and remove the nut, washer and hub assembly. Important – ensure the long (steel tipped) alloy pushrod and the thrust washer between the basket and hub is still in place or you’ll be buggered. Now fit the new hub.
Problem number one – you’ll notice that the hub nut and washer will not now tighten down because there aren’t enough threads on the countershaft. This is because the Slabside hub has a thinner base and the Slabside countershaft is shorter, so this is where the spacer is needed on the driven shaft. Fit it over the shaft, then you can secure the new hub using your original nut and washer using special tool no.2 to hold the hub while you tighten the nut to the correct torque (140 to 160Nm or 102 to 115ft-lbs).
Now re-fit your original clutch plates (as long as they’re not fucked, check the fibre ones for the correct thickness – 2.52 to 2.68mm / 0.100” to 0.106”) and check the steels for warpage using a feeler gauge and a piece of plate glass (max limit 0.10mm / 0.004”), starting with a fibre one, then steel and so on (you should finish with steel, if you’re not a complete wazzock). Now fit the extra fibre one you’ve just bought.
Problem number two now rears its head – because of the differences in the length of the countershafts, your clutch push rod is now, effectively, too short. This is where you fit the ball bearing – it will take up the gap between the alloy pushrod and the push piece. Fit your push piece complete with its thrust bearing and washer and then fit the new pressure disc using the new spacers, springs, washers and bolts and secure the bolts in a criss-cross pattern to the correct torque setting (11 to 13Nm or 8.0 to 9.5 ft-lbs).
Re–fit the clutch cover, check the oil level and you’re away! You’re now the owner of a coil-spring clutch – told you it was easy!
Now, extra hints and tips.
Tip 1: When you do the job, put the bike on its sidestand and carefully lift the front wheel and chock it on a brick – this will stop you losing any oil when you remove the clutch cover.
Tip 2: When buying new clutch plates, use only genuine Suzuki parts – I know they’re more expensive, but it’s false economy to put cheapo plates in. I know, I’ve tried ALL the super-trick/heavy-duty ‘performance’ clutch plates and they just don’t compare with the genuine stuff. You have been warned!
Tip 3: With this particular conversion you fine-tune the biting point by changing the ball bearing – if it drags too much (assuming you’re using the correct grade oil and the steels aren’t warped), then you need more travel so try fitting an 11.5mm one instead. If it slips (assuming the fibre plates and/or the springs aren’t worn), you need less travel so pop in a 9mm one. It really does make a difference!
Also take the time to make the special tools, they’re a piece of piss to make, and really make life easier.

Special tool one: You’ll need two pieces of steel bar that are 200mm long, 25mm wide and 5mm thick (ish …), drill two 6mm holes in each bar with the centres 165mm apart then, at one end of each bar, fit a M6x30 bolt and secure it tightly with a nut on the underside. At the other end, open out the 6mm hole to 8mm and join the two bars together with a M8x70 bolt and loosely secure it with a nut on the underside.

To use it, the M6 bolts will neatly fit into the slots on the diaphragm pressure disc and the M8 bolt will fit straight into the swingarm spindle – once the slack is taken up, you’ve got both hands free to undo/tighten the big 50mm holder nut!

Special tool two: First get one 400mm long piece of square section (20x20mm) bar and two old GSX-R clutch driven (steel) plates. Put the plates on top of one another and drill three holes equally around the diameter and secure them to the square bar using two M6x60 bolts and 20mm spacers and a couple of M6 nuts (this way, you can support the basket really well and reduce the chances off slipping, as the plates will be deep inside the unit). Finally put a small M6x10 bolt and nut through the remaining hole to secure the plates together. This is a wicked tool to have, when you’re trying to remove/secure the hub nut at 160Nm!

Tuning your Kat – the basics

A standard Kat is nice as standard, and a valuable classic as is, but it’s very hard to resist the temptation of modifying it. You can hardly find one that hasn’t been tweaked to the max. In my point of view for a Kat to remain a Kat you have to retain the standard fairing, tank and frame. So here are some of the options…

Engine tuning

Well, what can we say about tuning GSX1100 engines other than the sky is the limit? Thanks to the immense popularity with drag-racers you can build an entire engine completely from aftermarket stuff.
It has to be said that the drag bike guys have been moving more and more towards the GSX-R/Bandit engines purely because the supply of fresh engines is becoming more scarce. The most popular tuning method for a GSX1100 engine is the big-bore kit in combination with a top-end overhaul including a headflow, hotter cams and maybe bigger valves. A good excuse for taking such action is when the engine starts burning oil after churning away lots of miles. Anyway, you could go on and on about the options and still only cover 50% so I won’t go with that.
Many people are opting to fit an 1127 (GSX-R) engine, which is a dead shame for people who love the old GSX1100 engine, but a very good alternative if you’re after a low-mileage and reliable power plant.

Chassis tuning

Front end

From Suzuki’s point of view a headstock is just two bearings holding a steering stem (won’t argue with that 😉 and so they felt little need to change it’s design and dimensions during the last few decades.

That means that about any Suzuki front-end will fit the Katana… you’re free to interchange the front-ends of Bandits, GSX-R’s, Katana’s and GSX’s from about every capacity class, and even a CBR600 front end mixes in. Just remember to swap the whole front end incl. yokes and it’ll be a very straightforward swap. Keep in mind you’ll possibly lose some ground clearance after fitting smaller 17″ wheels and somewhat shorter forks.

Rear end

The space between the frame rails is 240mm. You need 30mm for the (25mm) chain to run free between the frame and the tire and 30mm on the other side to keep the wheel centered. So your maximum tire width = 240 – 30 – 30 = 180mm
To get there you need to move the sprocket outwards using an offset sprocket and maybe a spacer or two.
People who want to go wider than 180, like dragracers, need to widen the frame at the swingarm pivot and fit an outrigger bearing to the driveshaft (to keep the bending forces in control).
The hub will probably also need modification to bring the chainwheel closer to the inside.