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Home Repair And Restoration

CBF125 Oil Filter And Strainer Clean - Again

Job Date 18 December 2019

By Ren Withnell

So I've done the tappets again recently. I've cleaned the front wheel's bead again recently. And now I'm going to "do" the filters on't th'owd knacker. I think it's this weather you know. Where is the challenge, the jeopardy, the drama in tinkering with motorcycles on a pleasant sunlit summer's evening while sipping tea and listening to the tweety birds?

In the dark we can make out the crankcase of the engine that is wet on Ren's 125
It's cold and dark and wet. Tinker time!

Obviously I much prefer to be swaddled in layers, condensation dripping from the shed roof, rain and wind battering down, cold gnarled hands black with oil and all lit with a cheap flickering torch. Yes, this proves that I'm a real tough biker bloke and the ladies will be so impressed! I'm delusional again aren't I - it must be the cold.

Experience shows these things come and go in waves. Partially due to luck - this breaks then that needs looking at and the other is overdue. Partially because when you do a job on anything you find other things that are broken, need servicing or are worn out. And partially there are times I just get my tinkering head on so while I'm in the mood it's best to get things done because I won't always be in the mood.

Unfortunately the CBF125 does not have a "typical" filter. Presumably in the interest of cost savings and providing work for Honda dealers the CBF125 has a fine gauze filter at the oil pick-up and a centrifugal filter on the end of the crank. These are accessed by removing the right hand side crankcase. 

There's a lot of bolts but having been in here before and having wisely applied copper-slip to the bolts last time all the bolts come out just fine. The gasket remains intact too, I suspect this is due to my greasing it last time. Lube everything, then lube it some more just in case. Except brakes, not brakes, lubricated brakes aren't good. "Sorry officer but I really really REALLY could not stop for that red light..."

The engine with the cover off, we see the clutch, centrifugal filter
12 bolts and a little wiggle and we're in.

The little filter at the bottom of the motor, the pick-up gauze, is dirty. I take it inside, shine a bright light on it and push the muck around to see what is what. It feels like muck and I can't see or feel anything metallic which is a very good thing. I wash it in the sink, dry it and return it from whence it came. 

The gauze has a layer of black crud
The shiny parts are from the camera flash. I could feel no metallic flakes.

The centrifugal filter has a small amount of dry hard gunk wedged around the edges, and no more. Considering this hasn't been done for around 36,000 miles suggests it does not need doing all that often and / or the oil is doing it's thing correctly. I scrape out the gunk and wipe everything with a rag.

Around the outer edge of the centrifugal filter is a thin layer of hard gunk
The gunk, circled, can be scraped off with a screwdriver. Don't forget to clean inside the cap too.

Replace the cover, adjust the clutch, replace the oil and that's it, job done. I'd kept 2 evenings free for this task, so, erm, what should I do tomorrow night?

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Reader's Comments

Borsuk said :-
If you want i'll get number 4 stepson to bring my 125 over and you can set the tappets. :-). Just so you don't get bored.
20/12/2019 22:06:11 UTC
nab301 said :-
The last time I dismantled a centrifugal filter was in the 70's on a Honda C50 project I was working on ( under 16 at the time ..) The filter recess was completely full!
24/12/2019 17:55:15 UTC
nab301 said :-
The last time I dismantled a centrifugal filter was in the 70's on a Honda C50 project I was working on ( under 16 at the time ..) The filter recess was completely full!
24/12/2019 17:55:15 UTC
Ren - The Ed¹ said :-
I'm guessing that poor C70 had a rough life nab301! My CBF125 has enjoyed regular oil changes and now regular top ups so I figure that's why I haven't much sludge or muck in there.
25/12/2019 07:17:23 UTC
said :-

11/04/2023 16:38:40 UTC
nab301 said :-
I removed the filter on my late 2019 CB125F example recently (21k km's) . The centrifugal filter had even less debris than yours but the mesh screen was partly clogged on both sides.... oil changes approx every 1600km's from new.
Now all I have to do is remove and paint the swing arm , repaint the exhaust , foot pegs etc and it'll be ready for another winter!
Posted Image
10/05/2023 13:39:26 UTC
Ren - The Ed¹ said :-
21000 Kms, that's about 13000 miles. Seems like a fair bit of gunk in that filter. Mine looked the same and there was nothing obviously metallic in there, which leaves me wondering what the gunk is.

I wonder if the oil somehow coagulates the blowby particulates, I can't think of anything else presently.
11/05/2023 07:34:01 UTC
nab301 said :-
Ren , I've always imagined the debris to be mainly clutch(fibre plate) related .
14/05/2023 15:50:46 UTC
Ren - The Ed¹ said :-
Ah, yeah, durgh, did't fink of dat.
15/05/2023 20:44:05 UTC

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