Buying a CT-90
If you're looking for a used CT-90 or CT-110 (there are no new ones), here are some things to look for or look out for:
Frame and suspension
Cracks!
Because they look like "dirt bikes," many CT-series bikes have been badly, sometimes fatally, abused. The CT-90 was not a "dirt bike" in the sense of a ruggedized machine designed to absorb enormous blows and run off cliffs. Some people didn't know that, so the first thing you need to check for are stress fractures in certain critical locations. First, check that the footpegs and sidestand, which bolt directly into the bottom of the engine unit, are solid and that their bolt-holes are not cracked, split or stripped out.
Next, and you'll have to check carefully for this, the top mount flange, where the top of the engine bolts into the frame, must not be cracked, loose or rounded-out. The last thing you want to happen is for the transmission case to crack, because the next thing that will happen is that the engine will literally start to fall out. It happens only rarely, but it does happen. You should check the rear wheel mount flanges and the rear swing arms for cracking, bending or ripples and corrosion. If there are obvious repairs, such as a strip of metal reinforcement added to the swing arm, find out why.
There should be no leaks on any of the four shock absorbers. Ever.
Engine and transmission
Leaks.
You will probably find some oil leaks near the bottom of the transmission side covers. These are relatively common. More hazardous are leaks out near the final drive sprocket, behind the side chain cover. You don't want leakage there, because all of those seals are a pain to replace. It's air-cooled, so you don't need to worry about water leaks. Oil leaks on the head are a hazard, and there should be absolutely no fuel leaks at the bottom of the gas tank. This could indicate a split fuel line (not a big deal) or rust-through in the bottom of the tank (a real big deal). The carburetor will probably dribble a little, but see below for more information on the carb.
Plastic and trim
This isn't that big a deal, but cracks and missing or broken parts, and scraped side covers and rubber parts, indicate a bike that's been dumped or tortured. You can usually spot a dumped CT-110 because the turn signals will be trashed. On the CT-90, these were optional, so it's a little harder to track down. If the seat is split and the foam is eroding away, that's par for the course for an old Honda. They can be replaced or re-covered. A lot of these are held together with duct tape. The plastic side covers and the frame cover and headlight bucket are hard to find and expensive. What's more, the plastic compound is very hard to repair cleanly, so reject any advice that "that's just a little crack and it'll glue right up." It won't.
Mileage -- how much is OK?
Because it was often used off-road, you see very few high-mileage CT-90s, and I've never seen one with more than 10,000 miles. However, less than 1000 miles doesn't necessarily mean "a gem," because 1000 off-road miles of abuse are much worse for a bike than 10,000 well-cared-for street miles. If your intended choice has street tires on it, ask if the owner ever rode it off-road.
Special notes about the CT-90
The mounting flange for the muffler is quit prone to cracking or splitting down where it takes a 180-degree turn out of the side of the engine. If the side covers are missing, plan on replacing them, as the exhaust pipe there is hot enough to give you third-degree burn if you let a bare leg brush it during operation. A friend of mine carried a scar from my first CT-90 for nearly five years. The guards are not an option; if they are not there, you will pay quite a lot to replace them. They are sometimes available used.
The CT-90 tended to eat speedometer drive cables, so be sure to check it. If the cable is abraded, it will probably be corroded inside and will eventually bind and break.
If the rubber on the kick start is missing, you will have to replace it unless you like huge bruises on your shins. If the rubber pegs are missing off the foot pegs, you must replace them. This is a dangerous bike to ride without them! Open the side cover on the right side of the bike and see if the battery is in good shape. If there's a lot of corrosion or signs of battery crud, the bike was neglected or the battery was boiled dry. Replacement batteries for a 90 are around $29.
Check the castings on the handlebars. Make sure all screws are original and tight. If they strip out, you end up replacing the casting, complete with any switches in them, and they are extremely expensive. None of the cables (two or three brake cables, throttle cable, speedo drive cable) should have rusty cracks in the casing, or the cable will eventually break at that spot.
Starting and running
If you've never run a CT-90, be advised that the gearbox is not like most Hondas, where "neutral" is a position just above 1st gear. On a CT, you toe the gearbox all the way down until you get a green neutral light. You do not then have to click the gear partway up to reach neutral. Stranger yet, midway through the production run, sometime around 1974, Honda reversed the gear order, so that on early bikes you step down on the toe for 1st, on later bikes and all 110s, you step back on the heel for 1st.
A CT can be started in gear, but be careful. To start a CT-90 or CT-110, flip the choke lever UP, open the throttle 1/4 turn, switch the ignition on, and kick it over a couple of times. Assuming it starts, let it warm for 15 or 20 seconds, then slowly flip the choke lever back down. If the engine starts to stall out, bring the lever halfway back up for another minute or two. Once it settles down to idle, the CT-90 is a very quiet machine. You should easily be able to talk over its idle without raising your voice. You should hear a classic Honda OHC jingle... the valve chain should not be unusually noisy and there should be no buzzes or rattles.
Run the bike up the RPMS a couple of times, and it should throoooom like a Honda. If you hear clatter from the bottom of the engine, like a steel cup on a steel table, the crank bearings are loose and/or the piston is worn. Neither is all that hard to replace, but it's a consideration. Put the bike in first gear (one kick on the back of the gear lever with your heel) and nail the throttle. The bike should kick forward with no slippage and no hesitation. 1st has a ton of power.
Check to make sure the Posi-Torque is in the HIGH range. Start off, and run up through the gears to 4th. On a street, you should be able to continue to accelerate all the way through 4th gear. On a highway, you should be able to reach 50mph within one mile. If you cannot, or if it starts slowing down in 4th gear, you should check for low compression. Good numbers are 150. Great numbers are 165. Anything below 90 psi is unacceptable... the bike will need new rings.
Above all
As always, if the bike looks abused, it probably has been. I once bought a CT-90 cheap because the guy who owned it thought it was a 2-stroke and had put 40:1 premix in it. He assumed that the enormous amount of smoke and fouling of the plug meant the piston was shot. He was wrong.
Buying a CT-110
Most of the CT-90 comments apply here, but you should check that the turn signals are at least complete if not working. Later CT-110s had better carbs and electronic ignition that improved cold starting, so if you're going to look at a 110 on a cool day and it was supposedly well-cared-for, it should start with a minimum of fussing.
The CT-110 should be even more responsive than a CT-90, since it has about 10% more power. However, it's also about 10% heavier. The net result is usually a wash.
Last updated:
11/17/2001