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Knocking CBF 125

Blog Date - 03 January 2014

I love motorbikes I do. I also #####ing #####ing and #####ing well hate them too! (That's flipping, blooming and chuffing in case you wondered).

I was talking to a motorcycle mechanic recently and he noticed my CBF 125. "Great bikes them" he said "just be sure to use good oil, weak crank you see, don't like low revs". Yeah right. Everyone knows Honda engines are indestructible. Within 2 weeks of this statement and with 19,000 miles on the clock the dinky motor started to make a funny noise at cold on tickover, just after it's first started for the day.

"tick tick TICK TICK TICKETY TICKETY TICK TICK tick tick pause pause" and repeat. By the time it was warm it went away so I ignored it, just something a bit loose when cold.

After a few weeks and around 800 miles it was getting louder and continuing even when it was warm. It was also there more constantly at low revs. Diagnosis is proving difficult. First off it's not fast enough to be the crank, it's at a slower speed than the crank. And it's phasing, rising and falling, surely if the crank mains had gone then it would be constant. I trawled the net and found this on you tube...

WOW!! That's IT!! Sounds a bit like mine, being the clutch it would be slower than the crank too. Super. So I spend a small age and a small fortune purchasing a tool to remove the centrifugal oil filter and a second hand clutch basket. I remove my original clutch and inspect it. Nothing. Nicht. Nada. The clutch ring gear seen in the video is all find and dandy. I've been around it time and again in close detail and there's no sign of a crack or other damage. I put the bike back together and hope by some miracle that it's fixed itself anyhow. 


I ask at Rivi, my local biker haunt. Soon enough 5 or 6 experienced DIY mechanics all have various opinions on offer but the overall consensus is the crank's knackered. But what of the phasing in and out of the noise? What of it seemingly being slower than crank speed? Yeah but no but maybe like...endfloat...things moving around...etc etc. OK, I'm inclined to agree it's probably the crank. I use the bike the next day and it's noisier than ever and often it seems to be at crank speed now, even from low to mid revs. I fear I may not even make it back home without the damn thing seizing up. I do, thankfully.

It takes 2 hours and plenty of paraffin before the motor is clean enough to remove. It takes a further 2 hours to remove the motor. In fact it's an easy motor to remove but when you've never done something before it takes some time to suss what to do and what can be left alone. I reckon with practice this motor should come out in half an hour! The fiddly fairing sides need to be removed but the tank and injection throttle bodies can all stay in place. 

honda cbf 125 in shed with no engine in the frame
It's the ULTIMATE in fuel economy now. No rattle...fixed!

It takes another 2 hours of cleaning before I'm happy that the engine will not fill with dirt when I take it apart. As a starter I remove the rockers, cylinder head and the barrel, again all quite simple and logical. So there it is before me, the CRANK. It looks OK. It feels OK. There's nothing loose or rattly or out of place. 

Damn. And blast.

There's more to check, this has only been a cursory look. If it's phasing maybe I'll have to rotate the crank several times to see if it loosens then tightens again, I may be in the tight spot. It's possible it's one of the crank support bearings too. If it's not the crank I'm stumped, I truly am. It's not the gear box as it happens in and out of gear, whilst moving and stationary. I have considered the cam chain but that's usually a rattle, not a clack or a rumble. It's possible it's something in the top end but after a brief examination that all looks correct. 

I shall report further findings as and when I find them. In the mean time the motor sits in the living room and the bike sits in the shed, engineless.

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Reader's Comments

johyn de ville said :-
Ren, can you turn the crank with the impact driver I lent you, if so, you will be able to get it spinning fairly quickly, that might throw some light on what the problem is maybe
Ren - The Ed said :-
John...I can use my drill for that. I need to set it up properly otherwise I'll end up with oil everywhere...all over the living room!
Timmy said :-
My cbf is the same at 17000. Pre 3000 though it went into honda under warranty for this problem twice and both times they changed the clutch primary drive and end crank drive that drives it. Apparantly it poor machining that causes uneven wear causing the noise :-/

Ren - The Ed said :-
Hi Timmy. I don't know about the later CBFs but my '09 model was made in India. I guess any manufacturer can make a mistake but perhaps Honda India weren't quite on the ball with this part. I'm not aware of any recall about this though.
David mac Donald said :-
I have a cbf 125 , I also have some kind of similar noise, there fantastic on petrol, and are made of shite , Honda quality, if you take the fuel consumption out of it , and look at the so called quality of the product, you would not get one , if you say it's a Honda well they must be shit then ,you can't claim the name , then hand your customers this quality .
15/01/2016 20:09:22 UTC
Ren - The Ed said :-
Hi David. There is little doubt that my Indian made CBF 125 is not quite up to the same standard as the earlier Japanese models of the 90's for example. My own bike now has covered over 48,000 miles and is still serviceable so the quality can't be that bad!

I've heard of a handful of CBFs with this problem so it must have been a weak point on the early models. Other than that the bike seems to suffer similar niggles that most bikes do. Quality ain't what it used to be across all the marques.
16/01/2016 18:39:33 UTC
Bruce said :-
I work in a bike workshop and was given a CBF 125 with the strange building and falling knocking noise. The noise is not in sink with any moving parts as such and is very strange. After stripping off both right and left covers nothing was to be found. I suspected the clutch basket may be the culprit as it has a damper(cuish) between the gear and the basket. Two springs allow movement of the gear independently from the basket and I noticed that the assembly moved on the springs a little too easily. As it was possible to run the engine without the clutch installed that is what I did, obviously the oil cleaner must be installed back on the crank first and the cover put back on and most importantly the oil put back in. I started the engine and it ran silently which proved the noise does not come from the crank or piston etc. Because a new basket is £260 the customer asked me to rebuild the engine as it was. The clutch probably has rubber dampers as stops built in and I think they have shrunk or disintegrated (Indian rubber)and the mechanical noise is the metal to metal contact where the rubber has gone. Other than the noise I would think it will run forever with no new parts.
06/08/2016 17:28:17 UTC
Ren - The Ed said :-
Cheers Bruce. If you look around the site you'll see I ended up changing the clutch basket and all was well. The only thing is the old and noisy basket has no visible issues at all. I even fully dismantled it by drilling the rivets and found no issue.

I'm glad you posted your observations. I didn't find any signs of a rubber noise damper but that doesn't mean one shouldn't have been there. It's quite possible I could have continued with my old and rattly basket with no further trouble. I do use the bike a lot though and I didn't want to find out the hard way.

Do let me know if you hear any more regarding the customer's bike.

07/08/2016 21:30:34 UTC
Rob said :-
Did you ever get to the bottom of this noise?
27/09/2016 19:42:05 UTC
Ren - The Ed said :-
Yes Rob. Clutch basket or more specifically thr gear around the clutch basket. Use the search facility on the left, I covered it in a further post.
27/09/2016 21:45:07 UTC
Rob said :-
Thanks, I do suspect mine is the same after searching but was just interested in what you found before I take the cover off. Thanks for your response.
28/09/2016 09:52:54 UTC
Ren - The Ed said :-
I didn't "find" anything as such. Once I was happy with the second hand replacement I took the old noisy basket apart and could not actually SEE any cracks, breaks or problems. But the fact remains once I replaced the clutch basket the noise went away.

It's not too bad a job replacing the clutch basket BUT you will need a special tool for the nut that holds the centrifugal oil filter thing in place...GRRRR!

The big nut at the centre of the clutch basket is also incredibly tight. It *can* be undone by putting the bike in gear, stopping the rear wheel from turning with a big lump of wood and heaving like mad. But - I'd strongly recommend getting access to a ratchet/torque/windy gun. You know the thing...mechanics use them to overtighten your wheel nuts. Use the gun to UNDO the nut, don't tighten it back up with the gun.

Windy Torque Gun
28/09/2016 13:04:03 UTC
said :-

10/10/2017 21:36:06 UTC
vic2099 said :-

I can't find torque values for cylinder 4x bolts, and 2x bolts on side. Do you know them? (all bolts that are under Valve cover, those bolts for undoing cylinder head)

Please help.
02/11/2017 09:38:13 UTC
Ren - The Ed said :-
Hi vic2099. I'll have a look in my Haynes manual later when I get home.
02/11/2017 10:53:28 UTC
Ren - The Ed said :-
According to my Haynes manual the cylinder head bolt torque is 12nm. Oddly enough those are the long thin bolts.

The camshaft holder sleeve nuts are 32nm. Those are what most people would understand as the main cylinder head nuts.
02/11/2017 23:14:24 UTC

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