The outside of a motorbike engine seen up close near the exhaust

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CBF 125 Worn Out Clutch

Blog Date - 07 November 2017

I guess it had to happen, one day, eventually. 

On the road today I was climbing a gentle incline in fourth gear when the revs rose but not my road speed. I've known for a little while that the clutch has been "fluffy" and "woolly" so this has not come as a total surprise. I suppose after 68,500 miles on a 125 motor it has to be expected.

I pride myself on being gentle on clutches. In all my years I've only had to change one clutch on a motorcycle and that was soon after I'd bought it so the damage had been done by a previous owner. I've never had to change one on any of my cars. Despite my delicate touch nothing lasts forever.

The clutch basket and centrifugal filter on the CBF125I guess I can clean the centrifugal filter when I'm back in the motor.

Hopefully though I may be in luck. Waaaay back when the 125 was a sprightly 19,000 miles old I had to replace the clutch basket (Knocking CBF 125 Knocking CBF 125 Part 2 CBF 125 Back On The Road). As such I still have the old clutch basket and the old clutch plates and the old clutch springs. I think. I hope. I don't remember throwing them away but where they are in the house is another thing entirely.

I also have my Haynes manual. I should be able to ascertain the correct spring lengths and plate thicknesses and check them. Even if I cannot find my old clutch or the parts are well worn I can get an EBC set of plates for around £25, springs seem to be about £12 and a new gasket about £10. Obviously this is far far far more than I'd want to pay (£0.25) but I can manage it if I don't eat for a month.

This is not a disaster but it is a sign that the engine is getting shall we say - tired?

Have you got your own mechanical disasters? Big or small we'd like to share them here on Bike And Travels. Contact

Reader's Comments

Bob said :-
I don't know, a clutch is just a clutch - not sure it indicates anything about the overall state of the engine. That centrifugal filter does though, it looks remarkably clean! Chuck some plates in it and go for the magic 100K!
08/11/2017 08:44:13 UTC
Ren - The Ed said :-
Yeah Bob any clutch will wear out, they are a service item, a consumable.

You'll be pleased to hear I have found my original clutch so I shall be measuring the plates and the springs. I it's still within tolerance then they'll be going right in there.
08/11/2017 11:21:53 UTC
Christopher said :-
Let us know how you get on? The used clutch parts should be fine to use....My CBF125 has a 'mere' 25,000 Miles showing! Hopefully yours will go for some considerable time yet....Onward's to 100,000 then!
08/11/2017 07:40:40 UTC
Ren - The Ed said :-
I keep on thinking about the 100,000 mile mark Christopher but I still have 31,500 miles to go. Think about that - that's more than most motorcycles of any capacity do in their life let alone an already very tired 125 can manage. I dare not to dream because so much can happen between now and then.
09/11/2017 10:34:24 UTC
Andy Gray said :-
Hi Ren

So what does the centrifugal filter do? Filter the engine oil? Does it have a "normal" oil filter as well?
14/11/2017 08:56:27 UTC
Ren - The Ed said :-
Hi Andy. There is no "normal" filter on the CBF125. There is the gauze filter where the oil is collected from the sump. This will catch larger particles.

The centrifugal filter is as the name suggests! As the oil passes through the spinning plate of the filter I presume any heavier-than-oil particles are flung to the edge and trapped there, as you see in the image.

I suppose metal is heavier than oil. Hopefully clutch friction plate material is too. I will make some assumptions here. I am guessing centrifugal filters are less effective than normal filters otherwise more engines would have them. They're probably cheaper to manufacture otherwise my bike would have a normal filter.

I await for someone to put me straight on this.
14/11/2017 10:21:40 UTC
Andy Gray said :-
Looking more closely at the photo, I can see the gunk collecting around the edges.
15/11/2017 08:39:37 UTC
Ian Soady said :-
My Land Rover Discovery has a centrifugal filter as well as a conventional canister type one. Normal servicing routine is to change the centrifugal filter along with the oil at 12,000 miles and the canister every 2 oil changes although I do both every time.

I don't see why they would be cheaper in fact I'd expect them to be more expensive as the canisters probably only cost pennies for the bike manufacturer to buy. My Discovery filters both cost about the same to me.
15/11/2017 10:47:08 UTC
Ren - The Ed said :-
Spot on Andy.

Ian - the canisters are cheap enough to make but I wonder if the additional plumbing required to pump through the filter creates additional costs? The centrifugal filter on the 125 is stuck on the end of the crank.
15/11/2017 11:40:34 UTC
Bob said :-
To use a centrifugal filter you have to have a shaft to attach it to. Most car engines aren't in the correct configuration, but many bike engines could find room on the end of the crank-shaft if they wanted to.
Honda have used this system for years on their small bikes, I think the undidputed longevity of these revvy little chappies speaks volumes for the effectiveness of a roller bearing big end with pressure oil feed.
I guess it would only work for roller cranks because of the lower oil pressure, the feed from the clutch cover has to seal reliably at however many thousand RPM the crank is spinning, the ones I've seen use a spring loaded top-hat plunger - is the CBF similar?
Most manufacturers have moved away from lip seals on the cranks, the alternators now run in engine oil and there is no points plate these days. It makes for a more oil tight engine, my KLX engine has only a gearchange shaft and output shaft lip seal in its engine.

21/11/2017 10:48:53 UTC
Ren - The Ed said :-
If this is what you mean by a "spring loaded top-hat plunger" then yes. This is what's on the CBF125.

As per your KLX the CBF125 has regular gaskets on the engine cases but the only rubbery seals are the gearshift shaft and the output shaft.

The centrifugal filter's top hat plunger
21/11/2017 01:02:16 UTC
Ian Soady said :-
"To use a centrifugal filter you have to have a shaft to attach it to. "

The one on my Discovery doesn't - it's spun by the oil pressure. You can sometimes hear it spooling down when the engine is switched off. I understand it can spin at some astronomical speed.

But it would be difficult to find room for this type on the average bike.

Actually, come to think of it, the "sludge traps" in bikes like Triumph and Norton twins are in fact centrifugal filters. They're located in the crankshafts so pretty inaccessible and only cleaned out as part of a major overhaul. And they're usually packed with rubbish.

Item 3 on the attached (BSA version).

21/11/2017 02:51:26 UTC
Ren - The Ed said :-
Sludge trap? In the crank? Golly, some folks say motorcycle technology hasn't moved on much.
22/11/2017 12:08:43 UTC
said :-

08/07/2019 01:12:02 UTC
said :-

12/07/2019 03:06:32 UTC
Cryo said :-
If anyone wants to know, my official honda cbf125 service manual states:

clutch plates service limit (warpage)= 0.20mm (checking it with a feeler gauge on a flat surface

Clutch discs service limit (both A width front and back and B width 3 in the middle)= 2.80mm

Clutch discs Thickness= 2.92mm - 3.08mm

Spring free length= 39.0mm

You are welcome
17/08/2019 07:03:46 UTC
Ren - The Ed said :-
Cheers Cryo, useful stuff :)
19/08/2019 08:48:33 UTC
Phil said :-
Hi can anyone please help me I need to replace the clutch on my cbf 125 really struggling but I cannot find out the size of the castle crown socket needed to remove the centrifugal filter nut it’s a 2012 Honda cbf 125 I can’t do the job without it this socket really frustrating
26/01/2020 01:59:00 UTC
Upt'North said :-
Phil, I have no knowledge of this particular bike but if you check on the parts listing does it state the nut size?
You'll find the parts list on somewhere like CMS NL or Lings.
Hope it helps.
26/01/2020 05:50:44 UTC
Ren - The Ed¹ said :-
26/01/2020 07:00:24 UTC
Ren - The Ed¹ said :-
26/01/2020 07:02:01 UTC
Upt'North said :-
That's cheap, unlike your good self.
26/01/2020 07:02:56 UTC
Ren - The Ed¹ said :-
... or just google up Honda centrifugal filter removal tool. Common as muck, cheap as chips, just blooming annoying if ya ain't got one :)
26/01/2020 07:03:24 UTC
Ren - The Ed¹ said :-
Cheap? Me? Prudent sire, prudent.
26/01/2020 07:04:06 UTC

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