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Hi all!

New to the forum and just started overhauling my first old-timer, the Honda CB125k3 from 1969 or as I call it, my fat Rhonda. I bought it about 4 years ago but was not able to really look at it until now! The bike did ran with a top speed of around 80km/h. I'm completely new in motorcycles, so I hope to receive some tips on my ongoing maintenance. So far I managed to do the following:

1. Clean out the gas tank: removed the petcock, filled the tank with vinegar + salt, currently taking away the rust.
2. Cleaned the carburetors: installed new float on the R carburetor (float was damaged)
2a. I noticed the choke plates are missing/damaged on the carbs. Anything I can do about it?
3. Drained the oil
3a. I have one seized bolt on the oil filter cap. Had a couple of others on the alternator cap which I managed to remove with my impact driver. This one is completely seized. What's the best next step?
4. Camshaft tensioner. cant find the tensioner bolt. Is it possible it is not included on my model? Should be in between the two exhausts?
5. Ignition timing. Still to do
6. Setting the valves. Still to do
7. compression test the cylinders
8. Spark plugs that were still on are completely black. Will clean out and test
9. Battery is dead, to be replaced and to check all the circuits (main light, pinker lights, stop light,...). Any recommendations on the battery? It had a 6V6Ah.
10. Found back rectifier, condenser and ignition coil on the bike. Anyway to test these?
11. After the main repairs will repair the chrome and the paint.

See below a couple of pictures of the bike as it is now, workshop could be cleaner :)


312564


312565


Looking forward for tips and tricks!
Best regards,
Jef
 

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1. Clean out the gas tank: removed the petcock, filled the tank with vinegar + salt, currently taking away the rust.
2. Cleaned the carburetors: installed new float on the R carburetor (float was damaged)
2a. I noticed the choke plates are missing/damaged on the carbs. Anything I can do about it?
3. Drained the oil
3a. I have one seized bolt on the oil filter cap. Had a couple of others on the alternator cap which I managed to remove with my impact driver. This one is completely seized. What's the best next step?
4. Camshaft tensioner. cant find the tensioner bolt. Is it possible it is not included on my model? Should be in between the two exhausts?
5. Ignition timing. Still to do
6. Setting the valves. Still to do
7. compression test the cylinders
8. Spark plugs that were still on are completely black. Will clean out and test
9. Battery is dead, to be replaced and to check all the circuits (main light, pinker lights, stop light,...). Any recommendations on the battery? It had a 6V6Ah.
10. Found back rectifier, condenser and ignition coil on the bike. Anyway to test these?
11. After the main repairs will repair the chrome and the paint.
Hello,
ad 2a. I can't help
ad 3. there are tools to remove screws, I would prefer to give it to the workshop. It is a good idea to replace all screws for allen type ones after removal
ad 4. check FSM, tensioner bolt is horizontal (take a look on the picture at https://www.cmsnl.com/honda-cb125k3_model8199/partslist/E03.html)
ad 5. 6 and 7 do it after camchain tensioning.
ad 8. don't be greedy, buy new plugs.
ad 9. 6N12 battery is working at my bike for three years. Pay attention to electolite level and check charging voltage. Installing LED bulbs will reasult increased charging voltage. This will dry out Your battery (Front bulb replacement increase voltage to 8.5 V)
ad 10. Rectifier is a simple Greatz bridge. You can check this by most of modern multimeters. Coil and condeser tests are described in FSM


good luck with Your bike

Andrew JK
 

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If you don't have a Factory Service Manual (FSM) get one there are multiple places where they can be downloaded.
I don't have a 125 so I don't have a copy but I'm sure someone will be along shortly who can point you in the right direction.
The best peice of advice I can give you is DON'T Trust the You Tube Videos that are out there.
Many are just Hacks that will lead you down a bad path to destruction. USE the FSM as your bible.

If the Carb Choke Shafts are still in place you can Make your own Choke Plates.
Even the Spring Loaded Port Hole type if that's what your model carb had.
 

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For a Choke you don't even really need the spring loaded port hole.
All a Choke does is restrict the air flow to force a low pressure zone in front of the Throttle Plates.
 

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For a Choke you don't even really need the spring loaded port hole.
All a Choke does is restrict the air flow to force a low pressure zone in front of the Throttle Plates.
It has slider carb. Choke is done by slider restricting air inlet.
 
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