One of the earlier race inspired scooters by Suzuki, featuring upside-down Showa forks and Carbon fibre look dash panels, the Suzuki Katana was an instant hit and quickly became beloved for tuning, with plenty of doing race parts from Malossi and numerous other manufacturers.
Early Suzuki Katana's had the Suzuki air cooled engine in them, whilst later Suzuki Katana's had Suzuki's new liquid cooled engine, and where designated Ay50R for the race output version.
Motorcycle Parts Suzuki
One preponderant highlight of the Suzuki Katana's are their very low gearing, which means the engine does more revolutions per wheel revolution compared to other scooters, this provides very quick acceleration but a lower top speed, even on tuned engines, most other derestricted scooters can keep up on top speed, but will struggle to match a race tuned Suzuki Katana on shear acceleration.
Although some citizen see the Suzuki Katana's low gearing as a problem, it is also the scooters most strength, with blisteringly fast acceleration, most other scooters will struggle to keep up with it in an urban environment, as even when others are tuned and kitted up with doing parts they'll still struggle to match the Suzuki Katana's 0-30 times. When the liquid cooled Suzuki Katana is tuned it is approximately untouchable against all the other 50cc scooters on the store in these times, it'll only loose out on longer roads where speeds of 50mph+ can be achieved by other Lc scooters.
The Suzuki Katana's are primarily restricted mostly in the exhaust, so in the very early models it requires binning and replacing with a race exhaust, whilst in the later versions with a 2 part exhaust, you can grind out the internal restrictor cone and refit the exhaust, although nothing will match the doing that an aftermarket race exhaust gives for the Suzuki Katana. On the very early models, the Cdi is also restricted and requires replacing with an aftermarket model, although this isn't a problem on the later scooters.
As with my usual reccommendation, Gianelli Exhausts generally make the best doing exhausts for scooters, and since they're all e-marked, thoroughly road legal and come with a warrenty when fitted by an authorised mechanic, so are by far the best tuning selection for road going Suzuki Katana's, and all other scooters that are being tuned for the road.
When fitting a Gianelli race exhaust to your Katana, it'll need a slightly higher jet (0 to 2 sizes on non catalysed Suzuki Katana's, I don't think they made any with catalytic converters) and slightly lighter rollers, since doing exhausts allow the Katana to make more power but at a higher rpm. Going 0.5 - 1 gram lighter than appropriate generally does the trick for Gianelli race exhausts on the Katana's, but it varies in the middle of exhausts and tunes, and the Suzuki takes 17×12mm rollers.
After fitting a race exhaust, the biggest advantage the Scooter Katana will gain is by fitting a doing big bore kit, adding a 40% growth in capacity and more than doubling the power. Malossi and Polini make the best big bore kits available for tuning the Suzuki Katana, and will contribute the best doing and reliability compared to the economy big bore kits on the store . As you're increasing the capacity with the big bore kit, a bigger jet is required to be fitted in the carb, usually nearby 6-8 sizes larger, although doing a plug chop after a test ride to check the jetting is recommended to check your scooter isn't running lean after it's tuning, otherwise it can be liable to go bang.
When tuning your Suzuki Katana, it is prominent to make sure you run it on the best capability fully synthetic oil, especially with the Katana's oil pump system, as it can be prone to clogging up the exhausts, especially the appropriate ones. This is one of the reasons why fitting an aftermarket race exhaust to these scooters can contribute such a huge difference on older models.
After fitting the Gianelli race exhaust and tuned big bore 70cc Malossi cylinder kit, you'll have a exceptionally fast accelerating scooter, but without an remarkable top speed growth compared to other scooters, due to the Suzuki Katana's low gearing. You can now either keep the fast acceleration, or sacrifice a exiguous and fit a gear up kit to your Katana, allowing it to use some of this new found power in case,granted by your Malossi big bore 70cc kit to give you a best top end, good for someone else 10mph in most cases. Although it looses some acceleration by fitting a gear up kit, your scooter will still be faster accelerating than a appropriate untuned Suzuki Katana, so don't think a gear up kit will make doing worse than before.
For even higher increases in power, bigger carbs and aftermarket variators are available, but do not make as bigger differences as the Gianelli race exhausts, the Malossi big bore 70cc kits and the gear up kits. The variator will contribute a mountainous advantage if it is fitted onto a Suzuki Katana that is older and has done a lot of millage, as this combined with a new belt will give a lot smoother acceleration and a exiguous top speed increase.
Suzuki Katana Ay50 Race Tuning Guide