How can I get more speed/power/performance?
The easiest answer is, "lose weight."

Realistically, the CT-90 was never intended to be a speed demon. In general, about 50 to 55mph on the flat is all you'll get out of the CT series. In theory, the CT-110 has a little more power, but it's also heavier. Now, there are guys in Australia who actually race CT-110s (these bikes are called "postie bikes," because most of them are surplus from the Australian Post Office). There are 20mm Mikuni carbs, 3mm overbore kits, all sorts of things like that, but ultimately you have to own up to the fact that you're dealing with a machine that was intended as low-speed off-road hauling transportation. They did, after all, call it the "Trail 90," not the "Tearing Up The Street At High Speed 90."

One idea you shouldn't bother with is extensive resprocketing. If you start taking teeth out of the rear sprocket you'll probably lose top speed, since the engine really doesn't have the high-end torque to get the bike over 60mph and putting in taller gears will just make the torque problem worse. High-flow carbs and polishing the ports in the head might help airflow, at the cost of fuel consumption. There isn't much opportunity to lighten the bike, except for removing the lights, rack, front fender and maybe the center stand (the side stand is integral with the footpegs) and there's not much you could drill out without sacrificing strength.

If you're really serious, look around in the CT-90 list archives. There are some topics that deal with performance mods. Ultimately, though, you'll find the bike is just not good at high speeds, and at lower speeds it has all the power and torque it needs to climb hills if it's tuned up and has a good clutch. Live with it.

Stuff you may see out there

There are a couple of people selling Mikuni 20mm "racing" carbs on eBay. They come up from time to time and may be tempting if you think you want to spice up a CT90, but be advised that we don't know anyone who has actually gotten one of these to work in a CT-series, at least not any better than the factory Keihin carbs and often somewhat worse, because jetting them is a real pain. If you want to go that route, be advised that you should make sure that it will fit your bike before bidding or buying, and ask the seller if they can supply the name and email of someone else who's bought one and gotten good results out of it.

There are some crate motors out there that will fit a CT90. PowerBikeUSA has a crate 110 motor (available as either manual clutch or autoclutch 4-speed, with electric start) for around a thousand bucks. Good clean CT90 motors are out there for far less than that, but the 110 kit would offer better performance. Check them out.

Last updated: 03/03/2002