1975 Honda CB125S and 1981 CM200T

After getting it all cleaned up (not easy), I did some painting and not award winning "finning".


The rest of the engine started shaping up as well.

I cleaned the piston head, the valves, and did a deep clean on the exhaust port (I guess that's what it's called??). I lapped the valves and hopefully didn't over-do it. I put it all back together with new gaskets and o-rings, set the timing, and hopefully she'll run better than ever... at some point down the line.

As I read what I've recently written, it all sounds so easy. It wasn't. I was constantly searching up stuff on this site, studying YouTube videos, and trying to read between the lines in the shop manual. It was slow going and I had no idea what step was going to be the next step until I was there. It was mentally exercising, physically exhausting, but damn it was fun. At some point I had unscrewed the timing chain tension bolt ALL the way. Not understanding how it worked, I thought I could just screw it back in as the last step of re-assembly. By some crazy chance I just happen to see a little washer just laying there, beyond the magneto. It was from the tension bolt assembly. At that point I knew I was screwed. I was trying to avoid taking more stuff apart, especially after getting things looking somewhat normal, but the whole magneto assembly needed to come out. That required a master class figuring out how to do that with the basic tools I have. I got it out (front axle I think) and started looking for the parts to the tension bolt. I found them all... but one washer and I was convinced it had fallen into the gear box. OMG! I searched with needlenose pliers, magnetic screw drivers, flashlights, picks, etc in the tiny little areas I could see in. The was a small hole that was the perfect size for the washer to fall into, but I found nothing. I knew this would bite me in the ass if I just left it in there, but I really really didn't want to split the case and open up the bottom part of the engine. I re-assembled the tension bolt mechanism with an extra washer and put the magneto back in. I hadn't decided what to ultimately do, but in that process I saw that the missing washer was stuck to one of the magnets on the magneto. Thank god! I had just wasted a couple hours trying to find that washer and several more removing shit, pissed off the whole time, but at least I knew it wasn't in the gear box and I could move on. I pretty lost a full Saturday (or it might have been the whole weekend), but I was so happy to move on.
Next was removing 40 year old grime and rust off the frame and some of the steel parts. It took some wire brushes, a variety of soaps, and ultimately (against my desires) some gasoline. Not great for the environment, but gas and some elbow effort is an amazing grease and grime remover. It was worth it after I saw the nice coat of paint. Going the economic route, I chose to paint these with black appliance epoxy paint. The frame I had wire brushed all the rust off and painted directly. Some of the parts, like foot pegs and kick stand, I primed with self etching and then top coated with the appliance epoxy.

Before: 5vzm4JDaS8y8qGl0GK1X%A_thumb_27a0.jpg
After: H+4OrZOPTYWAIy4Nm4BNeg_thumb_27a2.jpg

Not a good shot of the frame drying, but you get the idea
Still so much to do, but I'm getting close to starting the process of putting the pieces back together. There is still a lot of parts cleaning as it comes together but I'm excited to be on this side of the hill. Critical point in the process... now, which part goes where??

This is not even near being all the parts, but you get the idea.


Well-Known Member
Good job of labelling. I find that going back together can go faster than coming apart as you know now how it goes. The worst for me was three-day searches for the next part in the assembly, giving up and ordering a new one, then spotting the mischievous part snickering at be from a shelf where I had lain it to be obvious.


~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Looks good, wish I took my time with my build.

Actually I did take my time, (money and all) was just to lazy to clean and shine and stuff.

Just tore my little CB100 down to the engine case, and built it back up to have something to play in the back yard on.

China virus cause my plant to shut down a bit, so beer and this little thing on a beautiful day, equaled a crack rib.

But still, fun anyways.
Yes, I must admit, the amount of cleaning has been in a pain in the ass... every time I think I've rounded the corner, I find another part with 45 year-old gunk baked on it and/or a ton of rust. That said, the most rewarding aspect of this project is when these parts start to look new or sometimes better than new. No-Pain-No-Gain applies here, too.


Well-Known Member
Yes, it takes years for the crud to build up, layer upon layer. It's unrealistic to expect it to come off in one operation.

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