1975 Honda CB125S and 1981 CM200T

SpaceTrucker

Active Member
After way too many weekends cleaning and prepping a dirt floor garage... I'm finally about to start working on the bikes. They haven't been started in many many years and a lot needs to be done before I can even ponder what kind of personalization I'll add to them. For a little backstory, here is my intro: https://www.dotheton.com/index.php?threads/howdy-from-austin-texas.77001/

They have not run in many years. Looking the bikes over, I know I'll need to clean a ton of rust out of the tanks, rebuild the carb, rebuild the forks, refurb or replace the cables and chain, and lots more. It will be a lot of work but I'm really looking forward to it. This is all a first for me, so I hope to gain knowledge from you guys but I'll try not to lean too hard to be a nuisance.

I think I'll try to get the CB125 running first.

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SpaceTrucker

Active Member
An older/wiser friend advised me to resist the urge to buy a bunch of parts before I get into working on it. When he first told me that, I thought it sounded pretty obvious. Then I started researching stuff, and it is very tempting to start ordering stuff based on a hunch that you'll need it. I've ordered a few things already and the cost adds up quick, so I see the basis of his advice. :) Like many of us, I hope to do this on a shoestring budget. That said, I don't want to prolong the process by not ordering obvious stuff I need, especially if its relatively cheap. So I'm looking them over and making an initial parts list.
 

SpaceTrucker

Active Member
The TwinStar (CM200T) once ran great, so I have a feeling that a thorough cleaning and cable refurb will go a long ways to get it running in some form or fashion (the throttle is currently stuck). The CB125 never ran that great so it may need a little extra help in the engine. Looking at the engine, I'm seeing dark grime/oil at the base of the cylinder head. Is this a sign I need to replace the head gasket? I imagine it is, but again... I'm new here. :)
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pidjones

Over 1,000 Posts
Most Hondas are in general not oil leakers. I have seen a ton of fork seal failures on them, though. And the hydraulic disk brake will be something to at least bleed like crazy or if that fails prepare to rebuild MC and caliper plus replace lines.
 

SpaceTrucker

Active Member
Thanks for the manual. I recently bought a Clymer for this bike as well, so between the two, this should help a lot.
Thanks for the tips, guys.

Trek97, I just started reading thru your CL100 thread. I can't believe that tank! I look forward to studying your thread as I can already tell it will have some good tips. Shop lamp as a heat lamp is brilliant! I have one and have always cursed the amount of heat it puts off.
 

SpaceTrucker

Active Member
Last night I finally got started. I took the seat, tank, airbox and carb off. The tank sounded like it had sand in it when I moved it. I was expecting this because it's super rusty, but I don't see any signs in the paint that it has rusted through. To my surprise, the carb was full of gas! (or what was formally gas, now more like a thin pancake syrup) I am pretty confident that this motor had not been run in the 2000's, but certainly not in the past 10 years, so I was not expecting anything liquid in there. I actually think this might be a good thing because all the barnacles and varnish seemed pretty soft and hopefully will brush off easy.
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SpaceTrucker

Active Member
One of the initial problems I had was pulling the throttle valve assembly out of the carb. Is there a trick to getting out? The manual acts like it should just pull out. I have it sitting in carb cleaner so maybe that will free it up if it's just stuck. The picture is just to show you how far I was able to get it out. It's more submerged in carb cleaner now, but not completely dunked. I'm hoping to free the throttle cable and then do a proper disassemble before I give it the real dunk. I was also going to try to clean it with a nylon brush as much as possible before the big dunk.
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SpaceTrucker

Active Member
I hope I can restore this carb. My goal is to refurbish as many of these parts as I can for cost reasons among other reasons, like... reuse is generally a good motto over buying new. Also, it seems the parts are either very expensive or knock-offs that aren't quite right. I don't mind using knock-offs... except for critical parts like that carb. That said... this carb is super nasty. This pict is after I scraped it a little with a screwdriver and a lot of carb cleaner sprayed on it, but no real cleaning. Most of the crap seemed fairly loose.
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trek97

No Custom Title
DTT BOTM WINNER
Soak it long enough and the slide will slip right out. Also after soaking the body, spray w penetrant warm w heat gun, helps to melt the varnish in threads, and gently remove and re-use as much original brass as possible. Even if you end up buying a new carb.
Carb medic works wonders, now I have a heated ultrasonic I use w pine-sol.
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Soak it long enough and the slide will slip right out. Also after soaking the body, spray w penetrant warm w heat gun, helps to melt the varnish in threads, and gently remove and re-use as much original brass as possible. Even if you end up buying a new carb.
Carb medic works wonders, now I have a heated ultrasonic I use w pine-sol.
Which ultrasonic do you have?
 

Maritime

Over 10,000 Posts
If you don't have an ultrasonic you can redneck one with a sander and a container. I use a tupperware style tub, boil pinesol and put it in, put a lid on and the duct tape a sander to it and turn it on. It shakes the shit out of the carb and gets a lot of crud lose. then I use carb cleaner and compressed air to get all the small passages etc.
 

pidjones

Over 1,000 Posts
I see no evidence of water, so no corrosion of the alloys. Should clean up fine with patience and judicious use of cleaners. I just bought a Chinese US cleaner for ~$125 and I'm pretty happy with it. I bought a 10 liter unit, but that's larger than most need. I wanted that big to hold a pair of GoldWing carb bodies still joined to save juggling the throttle and carb linkages. You can probably do most single bodies in a six liter unit.
 

SpaceTrucker

Active Member
Good to know you can get a small US cleaner for <$100. Or a big-ass-4-carb one for not much more! Fortunately I didn't need one for this (I think). Using a brush and some spray carb cleaner I got the big chunks off and disassembled. As Trek suggested, a heat gun allowed the throttle slide to come out. I dipped everything in a new can of Berryman ChemDip for about an hour and I can't believe how good everything came out. That stuff worked wonders.

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SpaceTrucker

Active Member
Today I ordered a new set of carb gaskets because I guess the first set I purchased, even though they listed "1975 CB125S2" as being compatible, must have been for a modern clone of the OEM carb. Bummer when you think you have the parts, but you don't.
 

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