1969 Honda CT90 Trail - Restoration/Renewal/Repair


unimpressed by you
I picked up another project, because I'm bored.

1969, Honda 90 Trail, in red.



It doesn't run yet. The previous owner hooked up a 12v battery instead of a 6v battery, so there's some burnt wires, and the coil is dead.


The coil (teal) is trashed, the condenser (yellow) probably is trashy as well. The selenium rectifier (red) may be OK though.

Should be a fun project, got most of the parts on the way already: used wiring harness, connectors, coil, condenser, battery, carb rebuild kit, etc.


unimpressed by you
Carburetor doesn't need anything, I suspect it's been gone through recently, as it's all fresh and shiny inside, and it's for a 73. But that also means I bought the wrong rebuild kit, oh well.

EDIT: Nope... It's the right carb. "T90KA, 4 Screw with "O ring" gasket. (Early Model)." That's an A not a 4, and it's supposed to have an o-ring seal for this year.

The bore of the carb is clean, the needle is in great shape, and the looks like it works too. The only thing that doesn't work is the "high altitude" pull knob. It doesn't stay in the out position, I'm thinking it's just something with the detent.

I may buy an ultrasonic cleaner finally, and drop it all in just for good measure.

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unimpressed by you
Looks like the coil may be bad, I need to find a manual for this thing. The selenium rectifier and condenser capacitor is though.

Here's some boring troubleshooting pictures:
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unimpressed by you
I don't really have all that much time. I get like 30 minutes here, an hour there, mostly when I'm dead-tired and can't really do anything.

Sometimes I wake up early and anxious and I just go out to the shop and knock something out really quickly. But that seems like it's happening less and less lately.


unimpressed by you
The Selenium Rectifier has been replaced with a new Bridge Rectifier, so I can be sure the battery doesn't go dead all the time, and it'll do a more efficient job than the old one.

I picked up a battery, but it came without electrolyte and apparently there's a shortage of battery electrolyte right now? So, yeah, it's going back to amazon, and I'm going to toss in a security system 6v 4.5Ah SLA battery instead.

I cleaned up the throttle assembly, and now it returns closed when you let go -- Kinda important. Just some brake clean, rags, teflon spray, and lithium grease.

I'm still waiting on the coil and condenser. Apparently that'll be here on the 8th? Woof. I really don't want to wait that long.

I decided I'm going to take a three four step approach to this:
1. Get it running, moving, stopping, and riding under its own power. Take it out, put some hours on it. Get it registered and tagged.
2. Over the winter, completely tear everything down, inspect, repair, restore, etc. Completely repaint the bike.
3. Use NOS or original used parts whenever possible, on the rebuild.
4. Keep it literally forever as an heirloom. It's already 51 years old, it's never going to be worth less.

I'm hoping I can get it running reliably and take it with us when we go to Rehobeth Beach this year, it ought to be a lot of fun out there.


unimpressed by you
Got a battery in last night, along with the wiring fixed for the lights. Now it's just waiting on a coil and I can fire it up!


I ordered a new:
Used 1969 Muffler
Period correct tires
Period correct chain
Reproduction Tail light assembly

And that should take care of the bare minimum to get it riding, and road legal.


unimpressed by you
Tail light and brake light wiring is fixed, now it actually works as expected, instead of just solid-on. Tail light now only comes on when the headlight is on. I had to clean out the light switch on the bars, and now it's silky smooth and actually works!

Now I just have to wait for some 6v bulbs... Apparently they're not easy to find, and I wonder if I should have converted to 12v because of availability in the future.

Some vertical video for your pleasure (one test light is 12-24v, one is 6-12v):

The backup wiring harness will arrive today, which I don't strictly need, but will allow me to restore it off the bike, troubleshoot with a known good harness and trace out any issues on the bench instead of on the bike.

The coil doesn't get here until the 6th. Super bummed out about not being able to ride it until then -- but probably it's just delaying my ability to diagnose what's wrong with the engine, lol.


unimpressed by you
Apparently I don't have a set of feeler gauges that go down to 0.002 as required to set valve lash, so I just kinda guessed. I got it to .008, determined it was about 1/4 turn from there to .005, and then gave it another 1/4 turn from .005. It was good enough to get more compression.

Got it running. It doesn't like to, lol. I'm going to tear down the carb tomorrow and maybe buy an ultrasonic cleaner finally. That would be a huge help with literally everything, firearms, jewelry, knives, car parts, etc. So, yeah, maybe... We shall see.

The engine had like 40 psi of compression when I started working on it. Threw some penetrating oil in the cylinder, did the valve lash, and got that up to about 85.

It doesn't want to start, so I have to do the ole-downhill-routine to get it to fire up. The spark sparks when it should, the carb is probably full of crud again, even though it was clean, and I even used new fuel line.

The transmission is another issue... It see to have an issue with engaging gears when under load, understandable, right? Well... This transmission is supposed to disengage the clutch as you shift... So. That might get interetesting. Although, I suspect it may just be a symptom of the carb not working right.

I did ride it, in the dark (has a headlight), in the rain, around the yard a bit. It's no faster than a bicycle right now, but we shall see how much change new jets in the carb makes.


unimpressed by you
Whooptie Doo.

It's street legal whenever the tag comes in the mail.


The NOS mirrors don't look horrible, but they're pretty dorky... Oh well, the whole thing is kinda dorky, I suppose that's the charm.


unimpressed by you
Good news:
I found a carburetor on Amazon yesterday, ordered it, and it arrived today. The jets were the right size, and it worked!


Bad news:
I broke every single piston rings. Apparently the emulsion tube actually was with the bike... Just inside the intake manifold/head.


OK news:
The piston isn't in bad shape, the cylinder isn't in bad shape either.

Slightly gloomy news:
Valve seat is probably torn up. This bike may or may not predate Honda using hardened valve seats, so I have to rebuild the head anyway...

This all explains why I'd get compression numbers of like 30, then get numbers of 85... Lol.


unimpressed by you
Engine is apart, cleaned, honed, and I took stock of how many gaskets and of which I'll need new ones.




Now, everything is in a box, all oilled up, waiting for the gaskets:

I could probably get away with reusing the head gasket #6, and the oil channel gasket #7, and using RTV for #4, but I know this bike is going to be loved by all (daughter, wife, passers-by, etc. so I should probably do it right. I really wish I had an ultrasonic cleaner, it would have been so much easier to get those parts marginally clean with one, instead of a pressure washer.

I found some sites where the original paint colors are listed, and I'm wondering if I should paint it factory red, or pick another color?

I got the front seat recovered and the "buddy seat" mounted up. It's not as ugly as I expected.



unimpressed by you
Hmmm, you make an interesting point. I kinda want to paint it the original color ease of a single stage paint and all, ya know?

But on the same token, I kinda want to paint it satin white pearl, and then paint the civic the same color. How cool would that be? Lol. Just, I'm not sure how I'd get both to the same place at the same time, so nobody would ever know.