Looking along a long straight road amidst lush green farmland
small image motorcycle loaded up with touring gear Home Contribute Contact BAT Chit-Chat BAT Facebook Page BAT Stickers! Ren's Biking Blog Sharon's Biking Blog Guest Posts Bike Reviews Bike Gear Reviews Bike Tips Travel Stories Travel Tips Repair And Restoration Interesting Links Support BAT
Home Repair And Restoration

Replacing The CBF125 Clutch

Job Date 10 November 2017

By Ren Withnell

So the CBF125 clutch is slipping huh? As previously stated (CBF 125 Worn Out Clutch) I still have the spare clutch from when I had to replace the original clutch basket. I am hoping...hoping that the spare is OK.

When I purchased the replacement clutch basket it came complete with the clutch plates. I cannot for the life of me recall whether I used my original plates in the replacement basket or used the whole lot. As such I have no idea what condition and mileage these "new" plates have. 

Task 1 - Clean. The typical definition of cleaning the 125 is riding it through the rain. However as I will be opening the motor on one side I don't want dirt getting into the motor. I spend half an hour with some petrol a toothbrush and the hosepipe removing ground in crud. Only on the relevant side of the engine you understand. 

Task 2 - Remove the crankcase. This has been off a couple of times before and I've copper-slipped the bolts. As such each bolt comes undone in a most satisfactory way and the gasket remains intact. Woohoo! 

The clutch side crankcase and the associated bolts on a wooden bench
Nothing broken - so far so good.
Inside the engine we see the clutch and the centrifugal filter
Hello old friend. It's been a while.

Task 3 - Remove the centrifugal filter. As I undo the screws I think back to Bob's comment regarding the amount of crud in the filter. Well Bob you'll be pleased to hear there is only minimal crud in the filter once more after 18,500 miles. Luckily I have the special tool required to undo the peculiar nut in the centre of the filter. I use a 1p coin between the teeth of the cogs to stop them from turning. I doubt this is a Honda approved method. 

The centrifugal filter has some muck within it but only a little at the edges of the disc
Not too much muck in there thankfully.
The tool for the centrifugal filter has 4 tangs on a tube
Why the strange nut affair? It's a conspiracy I tell you.

Task 4 - Undo the tight nut. Let me tell you a story. I remember when I first had to undo the nut at the centre of the clutch. This 17mm is TAF (Tight As ...). There is a special Honda tool that allows the basket to be safely secured while much heaving and hauling is carried out on the nut. The Haynes manual suggests making your own special tool. 

The nut in the centre of the clutch is really tight. It is circled in red.
It's just a nut, a simple nut. A really really tight nut.

Not I. Rather than go to the effort of creating a tool I spent days with various tools, wedges, levers and hammers trying to undo this simple nut. In my desire to make less work for myself I oft times create far far far far far more work. 

Eventually I borrowed a battery powered impact wrench from a friend. You know the thing, mechanics have a "gun" that goes "rat-rat-rat-rat-r-r-zzzzzzz!" usually air powered. This is a battery version. I didn't hold out much hope but I thought I'd give it a go.

"RAT-RAT-rat-r-r-rzzzzzzz". It took less than a second to release the tight bolt without using any wedges, clamps, grips or magic. I soon purchased a cheap Silverline mains powered version for about £40. A professional mechanic would scoff because under regular use its cheap construction would soon fail. I have only used it twice in 2 years, it is way more than adequate for my purposes.

The blue silverline impact wrench being used to undo the really tight clutch nut
The Impact Wrench is easily tough enough for this tough nut.

Today it takes longer to plug in the impact wrench than it does to release the TAF 17mm nut. There is no substitute for having the right tool.

Task 5 - Inspection. My concern is having stripped the bike the "new" clutch is in the same or worse condition than the presently fitted but knackered one. After removing the 4 spring retaining bolts the clutch pack slips out easily. I spread the "old" and "new" plates out.

While the "old" plates certainly look much darker presumably due to staining from contaminants in the oil they are not visibly any thinner than the "new" plates. According to the Haynes manual they ought to be 2.92-3.08mm thick with a service limit of 2.80mm. These differences are not obvious to the human eye. I do notice one (one, why just one?) of the plates is visibly worn more than the others. 

A bright clean friction plate and a dark dirty and presumably worn plate
Aging is a terrible thing. "New" V "Old"

I will take a chance and fit the "new" plates.

Task 6 - Reassembly. Note for anyone doing the task themselves. There are 5 friction plates, the outer two are different. Not in thickness but in the shape of the friction surface. Note the rectangles on the plates. Also note the outermost plate is "offset" with it's own slot in the clutch basket.

The inner plate has slightly less friction material than the outer plate
The outer plates have *slightly* larger rectangles of friction material compared to the inner plates.
The outermost clutch plate sits in it's own slot in the clutch basket
I don't know why - but that's how it should be.

I slot the "new" plates and rings into the basket. I remove them again because I forget the backplate (it's a Honda thing). I tighten the 17mm centre nut with the HAND HELD torque wrench. NEVER ever use an impact wrench to tighten things, it will strip threads in a matter of moments. I clean the centrifugal filter and tighten the weird nut to the correct torque. Replace the centrifugal filter cover, but not the crankcase cover - yet.

Task 7 - Clean the filter. Alongside the centrifugal filter there is a metal gauze filter at the bottom of the engine. I remove this is and see some crud and a sliver of metal. Hmmmmm. I wish that sliver of metal was not there, I have no idea where it has come from. What I am pleased about is that there is only one sliver of metal, no signs of any others. Not too shabby from 18,500 miles.

The location of the gauze filter at the bottom of the engine
The gauze filter is located here.
The gauze oil filter has a little dirt and muck on it and one sliver of shiny metal
Not bad, but where did that sliver of metal come from?

The Result? Better. Much better. The clutch is sharp once again and has that very small but significant little twitch that indicates complete lock-up. When things wear slowly you don't notice. I hadn't noticed that tiny teeny little jerk you feel when the plates stop slipping and full engagement is achieved was missing from the "old" clutch. It's back now.

I've given the CBF125 a damn good thrashing up hill and down dale and along the motorway and all appears to be well. Remarkably I'm not even leaking from the crankcase. 

Onwards and sideways dear reader. 


We'd like to share your mechanical tips, tricks, stories, disasters and ideas here on Bikes And Travels. Contact ren@bikesandtravels.com

Home Repair And Restoration Random Link

Reader's Comments

Pocketpete said :-
Well done looks pretty good. Is this clutch much different from the 500x.

I wear clutches out for some reason......
11/11/2017 20:56:20 UTC
Ren - The Ed said :-
The principal is the same but the details will be different. Theoretically it should be easier on the 500 as there's no no centrifugal filter but the TAF nut will be really tight.
11/11/2017 22:19:17 UTC
Ian Soady said :-
I've never needed an impact driver (usually my mature bikes have had most of their fastenings removed several times and some are wont to dismantle themselves whilst I'm riding along) but it certainly looks like a handy tool.

The problem is that I'm running out of space.....

Just to amuse you while we're on the topic of tools, I've been changing the springs on the rear units of the Guzzi as the ones fitted were far too hard. As those of you who have tried changing springs will know, it's tricky to compress them enough.

A tip from another forum was to butcher a mastic gun by sawing the end retainer through. It's exactly the right diameter for Girling / Hagon type springs. You can then use the squeezing action to compress the spring and very carefully remove / replace the retaining collets.

*****SAFETY WARNING******

It's essential to make sure that the two halves of the sawn through section are securely clamped onto the spring so it doesn't all fall apart and shoot the spring into soft bits of your anatomy - you can see from the photo that I did this in the vice. And also, never get your fingers near the collets - hold them in pliers so if the worst happens you won't mash them.


12/11/2017 10:34:00 UTC
Ren - The Ed said :-
HOLY COW! That...that looks bloody terrifying to me Ian. I think I'd be looking for something more substantial and secure than the friction mechanism of a mastic gun. I can just see fingers trapped in springs and high velocity metal fragments.

Nope, that's a nope from me.


13/11/2017 14:00:01 UTC
Ian Soady said :-
I did give a health warning, use the words "very carefully" and point out that fingers should get nowhere near.....

As it's held securely in the vice, there's nowhere really for it to go although releasing the tension is a little "interesting".

Come on, where's your sense of adventure?
13/11/2017 16:09:50 UTC
Ian Soady said :-
..... and of course you're only squeezing it by 10 - 15mm or so.
13/11/2017 16:10:34 UTC
Ren - The Ed said :-
Nowhere near to me would require being in a different room watching you through a plexiglass window.

My sense of adventure? I guess I must be really risk averse.
13/11/2017 16:12:40 UTC
Borsuk said :-
Ren Said: "My sense of adventure? I guess I must be really risk averse."

This from the man who aims his forks like a ballistic missile at his kitchen window when stripping them down.

Personally when stripping down high powered springs (I service my own air guns) I either use a sash clamp and velcro webbing to keep the lot aligned while I compress them. Or my home made spring compressor made out of a few bits of wood, velcro webbing, a couple of nuts and a long bolt.

13/11/2017 20:13:38 UTC
Ian Soady said :-
I did think of using a sash cramp to compress the spring off the unit then perhaps using strong cable ties to keep it compressed but decided that would be even more dangerous than my method.

I'd guess when you're several hundred miles offshore you need to be creative sometimes. Many years ago when I was an AA patrol, many of my colleagues were ex-REME and used to fixing tanks etc miles from anywhere. They too could be quite creative although this often involved the use of large hammers and Stillsons.

Coincidentally, I came across a blog where someone used a Spanish windlass affair to compress springs and that looks like another useful technique. I have to say I'm envious of the blogger's workshop which makes mine look very second-rate. And the bike is lovely.
cbsbritishbikebuild.blogspot.co.uk/2015/06/british-bike-special-build.html ...
14/11/2017 10:30:52 UTC
Borsuk said :-
This is at home Ian.

For some strange reason they won't allow me to bring my guns offshore. I think they know me to well at work and are scared I use the paraffin budgies for target practice.
14/11/2017 11:29:07 UTC
Ren - The Ed said :-
Have I got the wrong end of the stick here. Ian - the website you linked to shows the chap compressing his springs with a piece of ratchet strap material and a screwdriver!

Now - when I had to replace a snapped spring on my little Ford Ka I borrowed some spring compressors. By the time I'd compressed the spring enough to fit it to the Macpherson strut there was enough tension in it to launch a small motorcycle into geo-stationary orbit.

I presumed this would be similar for a spring on a motorcycle shock. While I understand cars are heavier and bigger I still figured there'd be a fair amount of tension even for a diminutive motorcycle. If people are using blooming mastic guns and bits of old rope am I right to guess there ain't much preload?
14/11/2017 16:42:38 UTC
Ian Soady said :-
The spring rates are 110 lb/inch (sorry about Imperial units but they are old springs....) and they need to be compressed about 1/2" to get the collets in, which would be a force of say 60lb or 25 Kg.

To be honest, if there was a significant force required I wouldn't be able to squeeze the lever enough to exert it as there's no real mechanical advantage. It so happens that I know my grip strength is 35 Kg and I wasn't using all of that although it was hard work.

I don't think you can compare car springs as apart from needing a much higher rate they probably need a lot more preload.

Yes, I wondered about the ratchet strap especially as that bloke has such a well equipped workshop including milling machine, metal bender etc and so on. If you follow through his blog you'll see he's quite obsessive about getting things right. If I had his facilities I'd probably have made some "proper" compressors. But of course this sort of job is not done very often.
15/11/2017 10:43:04 UTC
 

Post Your Comment Posts/Links Rules

Your Name

Your Comment

Captcha
Please enter the above number below




# 65000
image used for spacing
Valid HTML?
219
Admin
Classifieds