Tuning your Kat - the basics

A standard Kat is nice as standard, and a valueable classic as is, but it's very hard to resist the temptation of modyfying 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 dragracers you can build an entire engine completely from aftermarket stuff.
It has to be said that the dragbike 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-milage 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 tyre and 30mm on the other side to keep the wheel centered.
So your maximum tyre 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.