Honda CB-125S Oil Filter Help!

[PatioMechanic]

Hello, I just got my first project bike, a 1980 Honda CB125S, and need to change the oil in it. I have not been able to find any replacement oil filters online for this bike, and have even been unable to locate where it is in parts diagrams. I've seen several oil filter rotors for sale on ebay but again, no mention of the filter itself. Is it a screen filter somewhere that I just cant see? Does that require replacing or just cleaning? Any insight would be greatly appreciated.

[Riejufixing]

[Robby]

Get a workshop manual and have a look.
I doubt it has a normal paper element oil filter, small Hondas of that time tended to use a wire gauze that you remove and clean. Some of them also have a centrifugal oil filter on the end of the crank that you dismantle occasionally and scrape the crud out of it.

As to where you'll find all of these things hiding, workshop manual.

[PatioMechanic]

Big help, thanks! I found a workshop manual PDF that indicated a centrifugal oil filter that just needs to be cleaned out.

This was a barn find that was claimed to have run recently so I intend to restore it to working condition. I would like to eventually upgrade it to disc brakes, at least in front, and maybe do a sort of cafe racer look without going too overboard.

Thanks for the tips!

[Robby]

If you do change anything, don't cut the frame and keep the original parts. They're getting rare and prices are going up.

Also, disc brake would be a lot of work for little benefit. It would mean using different forks and front wheel.

Check the airbox for mice.

[steve the grease]

The CB125S was £199 in 1973, I opted for the more expensive dirt version the SL125 at £249. Either are a nice bike to own now. I can confirm that it's clutch cover off and impact driver out to scrape out the filter....

However The biggest thing that killed these bikes was the cam chain tensioner... it's a manual tensioner and owners tightened the tensioner up when the engine was cold until it ran quiet. The result was, that as aluminium casings heat up they expands more than the steel chain and the result is that the chain pulls the cam down into the head, trashing the bearing surface and as the cam runs in the head, effectively trashing the head and therefore economically the bike. - its why they went back to pushrods on the CG. You can find CB/SL's where the loose in the cam is more than the points gap, so the points will open and close at random.

So the secret is , only adjust the cam chain when the engine is warm, and even then only tighten it so it just stops rustling , you can hear the noise change.

The XL 185 engine is very similar. ( Fizzer , yeah you are right , I got my numbers wrong)
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All the above is my personal opinion, you can see my lips move, but I'm talking out of my arse.
I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....

[Fizzer Thou]

I bought a 1972 'K' reg CB125S back in 1975 as my first bike.The best thing I did was to buy a Haynes manual.

The gauze filter is under what looks like a tappet inspection cover down by the gear change pedal.Make sure that you note which way the sequence for reassembly is as I have heard of bits of debris blocking the outlet and reducing oil flow to the cylinder head

The centrifugal oil filter is indeed on the right side of the crank,under the clutch cover.Be careful to note where the dowels are as they can be easily misplaced.This oil filter is inside the cover held in place by three cross head screws.The oil sludge goes very hard and has to be dug out with a screwdriver.Be careful not to damage the gasket and do not hit the housing too hard with an impact driver to remove or to fasten the three screws.

As for the cam chain tension,I followed the instructions in the Haynes manual to adjust until the chain went quiet with the engine at tickover.This did not put undue pressure on the chain and the bike covered about 42,000 miles while I used it for the commute to Navy College.I must admit that it would have been far too easy to overtighten the tensioner though....

One problem that I did encounter one commute was the little pin in the end of the camshaft where the advance/retard mechanism goes,fell out under centrifugal force and the engine stopped.My only method was a bit final,but I found that if I slightly crushed one end of the pin it splayed out and I was able to knock it back in to place with a small hammer.It never gave me another problem.

I wonder where LMD58K is now

My first dirt bike was a Honda XL185SA and the engine was almost identical to the one in my CB125S,except that there was an electronic unit for amplifying the signal from a pointless pickup off the end of the camshaft.

I thought that the XL175 engine was a horizontally split crankcase,whereas the CB125S and SL125 engines were vertically split,as was the XL185SA
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Just talk bikes.What else is there?

Always have a 'Plan B'