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Discussion Starter · #61 · (Edited)
Okay, to answer your questions :

The cam chain is easily checked by placing the alternator rotor on the "T" mark then looking to see if the cam alignment marks are to - gether ~ they won't be .

The cam chain idler wheel is made of hard rubber, as long as NO VISIBLE WEAR , no bumps / cracks/etc. you can re use it .

The valve testing is also simple : assemble the valves, springs and so on then pour some gasoline in the ports, there may not be a drop of fuel leaking past the closed valve into the combustion chanber .

Typically in D.I.Y. jobs you'll see the edge where the valve meets the seat, begin to get damp after a few moments .

Test each valve separately then dry well with a clean cloth or paper towel before testing the other one .

When I said "hand lap the valves" I meant ONLY use the fine lapping compound .

You don't need Machinist's Blue for the home job, gasoline (NOT WATER !) will instantly show if you're good to go or need more lapping .

The pistons will almost certainly have worn ring grooves (called lands) so even if there's no longitudinal scratches / grooves they should be replaced to ensure the job is done to make it last ~ no fun doing all this only to discover next July it smokes again and you can feel the lack of compression in the kick starter .

How you approach the job often depends on your financial situation ~ I'm a Journeyman Mechanic so I can do as much as I want, others have to con$ider the financial outlay .

One last thing : your engine , like all Gasoline engines, burns the fuel, it does not ever "explode" it ~ exploding fuel inside the engine is called detonation or ping and is ruinous to the engine .
Thank you very much, I will carry out these checks and in case I will replace the necessary,
for the valves I will try tomorrow what you told me, ok then I better get a new piston and rings and do a job properly, obviously I try to save money but I don't want to do half work and have problems in the short term.

can you tell me instead if in your opinion the base of the cylinder and the head should be rectified in all cases to remove the remaining gaskets and make the surfaces shiny or can it be done with very fine sandpaper or other similar methods?

Thank you very much, I don't want to take advantage of it but you are helping me a lot
 

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No advantage taken ~ I'm one of those few who think that knowledge is useless unless freely shared .

Never forget that there are usually several different ways to do a job or approach any particular problem .

I forgot to answer you gasket question, sorry .

Don't use sand paper ! .

Use a toothbrush sized wire brush, this is called a "Scratch Brush" and is sold by welding supply places and Dollar Stores .

You want the one with steel bristles and it takes a while to get the job done, lots of filthy bits of gasket materiel all over you .

I use single edge razor blades held at a angle to try and get under the edge or and lift up, the old gasket first thing .

Then the wire brush until the metal on both surfaces is shiny and clean ~ be aware that those tiny black dots will cause weeps & seeps so keep after them but DO NOT GOUGE THE SOFT ALLOY SURFACE .

I don't often use sealants / gasket shellacks but others may have done so before you, if so use alcohol to soften up the old rock hard gasket before and during your scraping / brushing endevours .


I hope this helps, don't be hesitant to ask away, the only 'stupid' question is the one you didn't ask .

Others here will know things too, don't rely soley on my ideas .

I have a great deal more practical experience than most so my methods work but are not always when the dealer or book says to do .

Gather as much information as possible before beginning and study it, figure out what's the best way for you to proceed .

I know lots of "farm / field fixes" that will raise your hair so I don't often share those but again, they work .

Do you have a cell phone or other digital camera you can take pictures with ? .

Pictures always help, try to not shoot into the sun, good illumination is best, you'll get the hang of it .

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Discussion Starter · #63 ·
No advantage taken ~ I'm one of those few who think that knowledge is useless unless freely shared .

Never forget that there are usually several different ways to do a job or approach any particular problem .

I forgot to answer you gasket question, sorry .

Don't use sand paper ! .

Use a toothbrush sized wire brush, this is called a "Scratch Brush" and is sold by welding supply places and Dollar Stores .

You want the one with steel bristles and it takes a while to get the job done, lots of filthy bits of gasket materiel all over you .

I use single edge razor blades held at a angle to try and get under the edge or and lift up, the old gasket first thing .

Then the wire brush until the metal on both surfaces is shiny and clean ~ be aware that those tiny black dots will cause weeps & seeps so keep after them but DO NOT GOUGE THE SOFT ALLOY SURFACE .

I don't often use sealants / gasket shellacks but others may have done so before you, if so use alcohol to soften up the old rock hard gasket before and during your scraping / brushing endevours .


I hope this helps, don't be hesitant to ask away, the only 'stupid' question is the one you didn't ask .

Others here will know things too, don't rely soley on my ideas .

I have a great deal more practical experience than most so my methods work but are not always when the dealer or book says to do .

Gather as much information as possible before beginning and study it, figure out what's the best way for you to proceed .

I know lots of "farm / field fixes" that will raise your hair so I don't often share those but again, they work .

Do you have a cell phone or other digital camera you can take pictures with ? .

Pictures always help, try to not shoot into the sun, good illumination is best, you'll get the hang of it .

View attachment 70604 View attachment 70604
Thank you very much ... I like to find people who think like you, on the Italian forums it is completely different, people criticize and talk, often, without knowing, so I asked for help in this international forum ... end ot

I used exactly the scratch brush with steel bristles to clean the combustion chamber of the head and the valves from combustion sediments, could it be better to use the one with brass bristles or do I proceed with the steel one I have?

There don't seem to be any layers of sealant so luckily cleaning seems easier.

I have used in the past some razor blades (like cutters) to remove the gaskets from cylinders but I understand why you use the flush ones, you do not risk doing damage and cutting the aluminum from the cylinder

For the rest I am always grateful for the advice you give me, for the photos yes, I have both a mobile phone and a camera, I posted a couple of photos but I did not think they were of interest to you.

A question that you will surely be able to answer:
I forgot to order the valve cover gasket, I have gasket paper to cut out at home, can it be fine or does it need composite material like the others?

In the photo, am I wrong or is it a centrifugal oil filter like on my CB? when I opened it I found a lot of dry sediment which made me think that probably that filter has never been cleaned
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Discussion Starter · #64 ·
I forgot one thing, I can't find the "oil seal" of the valves, the one where the valves fit into the head, do I trust those already fitted? I'm afraid the engine will eat oil in the long run
 

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In a bit of a rush so pardon, O.K. ? . I have a B.Y.O.C. event to make...

Anyway, you have to install the valve stem oil seals and failure to do so means it will smoke blue/white whenever you close the throttle, should still run fine it's just bothersome .

They're prolly there but are also shot, they age out as well as wear out .

I'd wait until you get the correct & proper gasket, hand made gaskets are O.K. and I've done thousands but a proper, usually thin gasket is normally the simplest, easiest and best way to go .

The cylinder top gasket is a maybe make your own, I'd have to see it .

Pictures are always welcome and necessary as it helps us to understand better what you're doing, asking about, dealing with and so on .

Those guys who critisise & complain always ? that's because they're insecure and/or don't know so like all cowardly bullies, they make a lot of sound and fury but signify nothing, just beware .

The combustion chamber looks great , the sealing surface appears to have some gasket shellac on it, just keep at it with the steel scratch brush until it's clean .

One last thing : good supervision is critical :

View attachment 70606 View attachment 70606
 

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Discussion Starter · #66 ·
In a bit of a rush so pardon, O.K. ? . I have a B.Y.O.C. event to make...

Anyway, you have to install the valve stem oil seals and failure to do so means it will smoke blue/white whenever you close the throttle, should still run fine it's just bothersome .

They're prolly there but are also shot, they age out as well as wear out .

I'd wait until you get the correct & proper gasket, hand made gaskets are O.K. and I've done thousands but a proper, usually thin gasket is normally the simplest, easiest and best way to go .

The cylinder top gasket is a maybe make your own, I'd have to see it .

Pictures are always welcome and necessary as it helps us to understand better what you're doing, asking about, dealing with and so on .

Those guys who critisise & complain always ? that's because they're insecure and/or don't know so like all cowardly bullies, they make a lot of sound and fury but signify nothing, just beware .

The combustion chamber looks great , the sealing surface appears to have some gasket shellac on it, just keep at it with the steel scratch brush until it's clean .

One last thing : good supervision is critical :

View attachment 70606 View attachment 70606
No problem, when you can and calmly I wait for you, doing things in a hurry only creates problems, even under the supervision of the best😂

I try to remove them from the second head I have and see if any spare parts dealer has something

Unlike the other seals, this one was made of fine paper, exactly as you say, maybe tomorrow I'll post a photo but I think paper can be fine

Anyway you are absolutely right about those guys, in fact it was since I was 15 and the first 2t engines that I did not write on a forum for those reasons, I was pleasantly surprised by this forum and the people who write :)
 

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I don't understand why two images get posted .

I think I forgot to mention how important it is to remove every speck of that old gasket ~ isopropal alcohol and the steel brush works great, it evaporates quickly so get to scrubbing .
 

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Discussion Starter · #68 ·
I don't understand why two images get posted .

I think I forgot to mention how important it is to remove every speck of that old gasket ~ isopropal alcohol and the steel brush works great, it evaporates quickly so get to scrubbing .
ok thank you very much, tomorrow I proceed, anyway for the valve cover gasket to look good, I think it is not paper but sealant, as there is nothing left attached and there are points where the gasket would not arrive, I am attaching photos to show you this

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Discussion Starter · #69 ·
Today I carried out the valve seal test as recommended, seeing if by inserting gasoline there would be leaks, unfortunately the intake valve is leaking and it is necessary to lap it again (hoping to solve), I also ordered the standard piston + piston ring and gaskets valves guides, unfortunately for these I had to order them from poland as no one in Italy produces or sells them ... and they will arrive within a month from today.

In all cases it seems to me to be well advanced, I miss understanding if I can make the valve cover gasket with any engine sealant or if something special is needed (my friend tells me that there are engine sealants that do not have thickness and are made especially for these uses), as there was only the sealant from the original.
 

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O.K., I looked up your 1982 CB125S general export model Typ I (KPH) and it looks like there's no gasket there, you'll need a good quality HIGH TEMPERATURE sealant like Hylomar, sold in Moto shops under this name or "Hondabond", Yamabond" etc.

You need to run a very thin coat .

It looks like you're working diligently, cleanliness really is important .

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There you go ~

I use Permatex "The Right Stuff", it comes in squeeze tubes and handy aerosol cans, the trick with any sealant is to not over do it ~ you don't want any extra goo mooshing inside the joint .
 
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Discussion Starter · #73 ·
Thank you very much for the advice, after a long search I found the same permatex and ordered it yesterday (the others are not easy to find here), now there is just a long wait for all the missing pieces and I proceed

In the meantime, thanks to everyone
 

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With some patience and a little bit of money and effort you'll soon have a reliable Moto that's fun to ride and cheap to own / operate .
 
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Discussion Starter · #75 ·
With some patience and a little bit of money and effort you'll soon have a reliable Moto that's fun to ride and cheap to own / operate .
I hope so! I bought it 1 year ago now for my girlfriend's graduation gift, but I think she will still have to be patient 😂
 

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Discussion Starter · #76 ·
Hi, little update, I was unable to restore the valve seat but luckily I have a second head with which I tested both valves today and they have no leaks.

Then, bad news, the seller who sent me the new piston and rings was wrong to send me the rings which are 1.5mm thick instead of 1.2mm, so now I try to solve this umpteenth problem.

Luckily I have to wait calmly for the valve stem oil seals from Poland and therefore it is not a problem to delay the works
 

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Read the I-Ching and you'll understand patience, I know sometimes it's like pulling your hair out but once you learn how to research the correct part #'s parts, correct ones begin to appear much faster and more accurately .

My little CB125S, I've had it a while now ~ I bought it from my buddy who bought it new and set it aside until I retired several years later, got disheartened and gave it away, got remorseful and so bought it back and then the real fun began .

Now it looks decent and runs great, I'm having every so much fun with it, you may well keep your for yourself once you begin riding it .
 
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Discussion Starter · #78 ·
Read the I-Ching and you'll understand patience, I know sometimes it's like pulling your hair out but once you learn how to research the correct part #'s parts, correct ones begin to appear much faster and more accurately .

My little CB125S, I've had it a while now ~ I bought it from my buddy who bought it new and set it aside until I retired several years later, got disheartened and gave it away, got remorseful and so bought it back and then the real fun began .

Now it looks decent and runs great, I'm having every so much fun with it, you may well keep your for yourself once you begin riding it .
It is clear that you are a wise and expert person, who knows how many problems you have faced on engines!

is the US version of the CB125S two-cylinder, right?

In all cases I am very happy for you, it is a story with a nice ending, but who knows how many problems you have had to discourage you, but surely not a broken valve like me 😂
 

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It's easy once you come to grasp with the fact that motorcycles are constant maintenance toys.
 
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