Long Overdue Revival of my CT70H K0

I picked this HK0 up almost 10 years ago now with the intent to fix it up. More details can be found in this thread, if anyone is curious. We ended up moving a few months after I got this project, and I ended up buying way too many other Honda projects as well. This one got buried in the shed the last several years.

Here it was not long after I got it back in 2011. It really hasn't changed all that much over the years, except that I did put a tail light and bracket on it, along with an engine guard and muffler guard.



About 2 years ago, when I was working on my gold K0, I finally put together a parts list for the HK0 and got them ordered. I intended to work on the HK0 back in 2020, but then 2020 went to hell for a lot of reasons that I don't need to get into here. Then I proceeded to forget about the fact I ordered the parts until this summer.

So last week, I got busy. At least I have been able to upgrade my workspace since I last worked on this project!

I knew the wiring was a mess, so I decided to check all that first. What I found was rather entertaining, to say the least.

I started out by seeing if it would produce spark when kicked over, and I was amazed to find out that it did.

Some of the random clusterf----ery that I encountered with the wiring.







The black and red wires on the ignition switch were cut and then soldered together. Similarly, the three wires that would normally be soldered to the condenser were soldered together, but the condenser had been relocated and attached to the battery box. A jumper wire was used to connect the black wire out of the stator to the condenser and a few other wires underneath the seat. I am going to guess they hotwired it to run without a key, since it didn't have one when I bought it.

The coil wire was shot, as the end had been ripped off and the wire was abraded where it came out of the frame behind the airbox.

Since the headlight bucket was apparently removed in quite a violent fashion, there wasn't much there to inspect.

So, I just ended up completely removing the wiring harness that was there, and installed a replacement one. Then I spent quite a bit of time repairing damage to what was original. Got a bit of practice in soldering and using heat-shrink tubing, which worked out well, I think.

A few examples of repairs. There were a lot more!

Once I got through replacing/repairing the wiring, I hoped that I would still have spark. It took a little bit of fiddling, but I did get spark. And now I only have spark when the key is turned to one of the two "ON" positions, where before I had spark all the time, regardless of whether the key was present or not. I am not running a battery yet, so all the lights are disconnected from the harness.

While working on the wiring, I also cleaned the carburetor in the ultrasonic cleaner. It really wasn't that dirty, though there was a fair bit of aluminum oxide present.

Installed the "cleaned" carb, only to find that it wasn't as clean as I hoped (fuel wasn't able to get past the fuel filter passage), and it also leaked from the filter housing. The engine would fire briefly on a little bit of ether, but the carb would not pull fuel from the tank. Back when working on my K3, I ran into the same leak issue and never could get that carb to quit leaking. So, I had purchased a couple of carbs from Wincycles.

I installed the new carb and it fired right off!

I attempted to adjust the idle screw, only to find that I can have the screw fully turned in and the engine will still run. I am going to say I have an air leak somewhere...

The rubber boot from the airbox to the carb is shot, and I am missing the boot that goes on the rear of the airbox. Am I correct in assuming this is likely where most of my air leak is coming from?

I also will check the gasket between the carb and intake, as well as the gasket between the intake and the head, too.

Since I got the engine to run, I felt it was worthwhile to finish installing the replacement upper fork housing (the part headlight bucket mounts on) as well as the headlight bucket.

As I was reading up on how to go about this, I realized it was the perfect time to clean up and rebuild the front forks at the same time. Thanks to this thread (LINK), I learned which parts I needed. The photos helped a lot, too!

Off with its head!



I didn't lose any of the ball bearings, though two tried to make a run for it! They cleaned up real nicely and were able to be reused along with the application of a lot of fresh grease.

On with the replacement (though I am disappointed the paint is in not as great a condition as it was on the original part). Had to replace the nut at the top since the plastic was cracked on the original.



After much cleaning and liberal use of brake cleaner, I was able to get the fork parts to look like this.



I did a bit more cleaning up after this picture was taken as I wasn't satisfied with the result. I tried to sand off as much of the rust on the fork leg as I could with some 1200 grit sandpaper, too. The other fork was similar.

I'd say these parts hadn't been serviced since about 1970...the grease looked to be that old!

I did replace the slightly bent kickstand at some point in all of this, too.

Finally, I got to work on getting the new cables and replacement headlight bucket/speedo installed. It is not a CT70H bucket and speedo, but rather a set off of a CL90 that was in the salvage yard back where I used to live. The speedo is intact, and I confirmed that it works.

The wiring went together well until I ran into some extra wires I couldn't find on the CT70H diagram I was using. I looked up the CL90 wiring diagram and discovered that the speedo has a turn signal indicator bulb and a neutral indicator bulb, while my CT70H does not. So that solved the problem. I didn't take any photos of the headlight bucket wiring since I figured it wasn't that exciting.

Finally, we ended up at this point this afternoon.



After adjusting the brake cables and the clutch cable, I was able to start the engine and confirm that the transmission does seem to be intact. There is a little grinding of the gears when I shift, which I am thinking is mainly due to my lack of practice in using a clutch on a motorcycle. I will look into how the clutch adjustment is done, just to be sure.

I was able to terrorize the neighborhood for a little while as I was test riding this afternoon. I am very happy that I was able to revive this one. Like my other projects, this one still needs work. I am good at revivals, but not so good at finishing up loose ends with my projects (i.e. my K0, K3, and Z50R projects... )

At this point, I still want to do the following:

• Figure out where the air leak is and get that taken care of. Unless there is some other explanation for its strange lack of idle. I did replace the air filter, by the way.
• Adjust the clutch and readjust the clutch cable for smoother shifting.
• Readjust the front and rear brake cables.
• Get the new battery filled and charged so I can see how it runs with lights. I need to hear how piddly that horn sounds!
• Test the rectifier to make sure it functions correctly.
• Order some more parts (new fuel cap, rear brake switch spring, and a few others on the list so far).
• Change the oil and replace shift shaft and kickstarter shaft oil seals while I am at it. It likes to mark its territory in warmer weather, albeit slowly.

Nice bike!
Great work getting it cleaned up and running too.
Please clarify your carb issue...is it the IDLE screw, or the air/fuel screw?? I assume you're talking about the air/fuel screw. But either way, I don't think a air leak is the problem. I think that turning that screw all the way IN should cause your engine to run too rich...at idle. So if it doesn't go TOO rich, maybe you just need a bigger pilot jet.
Hopefully someone else will confirm this...and confirm that YOUR carb works the same as the stocker as far as the AF screw...in, is richer...out, is leaner??
You could try raising the needle, by lowering the clip...richer setting. See if that helps..?

When you back that AF screw out, at idle, does the idle change at all?? It should begin to idle higher at some point. If not, I would again think you need a bigger jet. But if it DOES idle higher...set to the highest idle, then turn back IN ¼ turn...done.

kirrbby said:

Nice bike! Great work getting it cleaned up and running too.

Click to expand...

Thank you!

kirrbby said:

Please clarify your carb issue...is it the IDLE screw, or the air/fuel screw?? I assume you're talking about the air/fuel screw. But either way, I don't think a air leak is the problem. I think that turning that screw all the way IN should cause your engine to run too rich...at idle. So if it doesn't go TOO rich, maybe you just need a bigger pilot jet.
Hopefully someone else will confirm this...and confirm that YOUR carb works the same as the stocker as far as the AF screw...in, is richer...out, is leaner??
You could try raising the needle, by lowering the clip...richer setting. See if that helps..?

When you back that AF screw out, at idle, does the idle change at all?? It should begin to idle higher at some point. If not, I would again think you need a bigger jet. But if it DOES idle higher...set to the highest idle, then turn back IN ¼ turn...done.

Click to expand...

Rats...I did mean the AF screw. I always call those things the wrong name!

Anyway, the idle speed does increase when I back out the AF screw. I just need to fiddle with the settings a bit more, by the sound of it. I haven't changed the needle height, and now that I think of it, I had to adjust it on the same type of repro carb that I used for my K3 resurrection. That may be the same issue here. Things I forget when I don't work on these motorcycles for a couple of years!