Looking across to the snow capped alpine mountains seen from the back seat of a motorcycle

Home Ren's Biking Blog

Knocking CBF 125 Part 2

Blog Date - 10 January 2014

Hmmmmmmmmmmmmm.....

So with the barrel off and the piston open to the air I invite a friend of mine over. SL's been tinkering with bikes for like 30 years and he's done a LOT more engine work than I have. It was him, and a few others, that agreed it was likely the crank that was on it's way out. He comes over on his trusty CG 125 and spends a small age looking, prodding, shaking and rotating the crank, conrod and piston. His final diagnosis after a cup of tea and some small talk is that there's "Nowt wrong with it". In fact he seems impressed that after 20,000 miles the piston, barrel, conrod and crank are in such good condition.

There's a part of me that's relieved and another part of me that's not. If it's not the crank and it's not the clutch then what IS it? SL has no better ideas than I have. I replace the barrel, top end and cover, I am absolutely flabbergasted how easy the motor is to work on. It's a doddle, an absolute doddle. The longest part of the top end rebuild? Finding a blinking washer off one of the cylinder head bolts. 

I take the alternator cover off...maybe it's something to do with the starter clutch. I fashion a tool to connect a 19mm socket to my drill and spin the motor with the drill. It all appears fine. There's not much to go wrong on this side, the alternator has fixed coils and moving magnets on the flywheel and a pickup for the crank positions. The starter clutch is behind the flywheel and although I'd like to inspect it I don't have the right tool and I can't really imagine what could go wrong to cause a knock. No. I replace the cover and nip up the bolts.

Back to the clutch. It can't be the clutch. It can't. The video in my previous article CLEARLY shows the cracked gear ring. I've inspected it as close as I can and there's nothing wrong with it at all. Still...I'll take it apart. So off comes the clutch cover, the centrifugal filter and of course I can't get the sodding basket off because I don't own an impact driver or the clutch removal too. Still...I'll spin it with the drill for the time being, at least I'll feel like I'm doing something useful.

It's there...clunk...clunk...clunk...clunk with each rotation of the clutch basket. It's hard to be sure that's it because the noise of the drill interferes with my desire to listen acutely. Still, I'm fairly sure it's there and with each rotation of the drill. It takes a while but I mark the clutch basket where I think the clunk is happening.

It takes another day before I can re-borrow the impact driver to remove the clutch basket. Big thanks to JA for the tool. After fighting and wrestling with strong arms and wedged bits of rags in cogs the impact driver goes brrrr.d.d.d.d whizzz! and the nut is of in less than a second. What an amazing piece of kit. I re-inspect the clutch basket. It's fine. Even the gf agrees she can't see anything wrong with it. Damn. Still, I purchased a second hand basket when all this started so as a matter of routine I fit the replacement.

Putting the motor back is is another doddle with the use of a small trolley jack and some wiggling. After nipping everything up and replacing the wiring I start the bike. Well, I don't. No electric. I check the fuses, the battery and everything else. What a muppet, I've not re-attached the starter motor wire or the earth wire. Buffoon. Click on the starter motor and without even a cough it starts and ticks over. While the tappets are sounding a little dry until the oil reaches them...the motor is...ahem...I'll just check...ah...erm...er...S.I.L.E.N.T!

In fact is sounds too quiet. No rumble. No ticking tappets. just a faint rustle can be made out between the beats from the exhaust. Wow. Amazing. Cool.

Before I declare all is well there is still much to do. I must check the tappets, they were far far too quiet so I need to make sure they're not tight. I've not given it a shakedown ride yet so there still time to find issues. It's going to take an AGE to replace the panels as this bike has had 5 previous owners all of whom must have been learners or did not make use of the stands, prefering to just drop the bike. There's not a straight fixing or an unbroken lug to be found. I want to at least get them something like. Finally I need to fit a new chain which I've ordered. 

Unless something goes terribly wrong I reckon we might be rollin' rollin' rollin' in another week. Wish me luck.

Reader's Comments

John De Ville said :-
Good to read you might have it sussed pal, Hindsight is a great thing and I say this because (and im not making this up) a good few years ago I thought that a crank was worn on a vespa, now I know two stroke vespa engines are much simpler but then an engine is an engine after all. I took the casings apart and checked all sorts and could not find any undue wear and tear in that engine but while it was apart I changed the cruciform, (that selects the gear cogs and they wear out and jump out of gear when they wear). I put it all back together as you have done and there was no rattle like there was before. the only assumption I came to is that a nut or circlip and become loose and on the rebuild I must have tightened it up or re seated it, ill never know but that engine never gave me any problems again. Lets hope that this might be a similar situation.


Best.
John.
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hi John

Yep...it's possible it's the clutch basket with a problem you can't see. It's also possible I've disturbed the cam chain tensioner and that's fixed it. It wasn't really a cam chain noise but then what do I know. Maybe I've disturbed a gear, moved a piston ring, dislodged a sticking bearing housing. Who knows!

I still THINK it's the basket, but I wouldn't stake my reputation on it.
01/01/2000 00:00:00 UTC
Frederik said :-
Hi, I seem to have the same problem with my CBF125, would you care to give my video a listen, and reply to me if the sound I'm experiencing is like yours. - From what I can read here on your blog, you also seem to have the sound kinda 'fading' out and back in. I also don't think the rhythm of the noise is valves or crank, since it just doesn't add up. I inspected the clutch outer ring from the outside, but I could not see a crack like in the video you posted in the first part of the CBF125 engine knocking blog.

Here is my video. I am looking forward to your reply.
https://www.youtube.com/watch?v=nChBWUybj70

Cheers, Frederik
www.youtube.com/watch?v=nChBWUybj70...
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hi Frederik

Gosh...er...diagnosis via youtube! I must say it does sound similar. I still have the clutch basket I removed from my bike and to this very day I still CANNOT see anything wrong with it at all. I can only assume the problem is hidden behind the plate that covers the dampening springs.

In my most humble opinion I'd replace the clutch basket. But please...if it doesn't solve the problem don't come ranting to me! I'm guessing, I'm not an expert in such matters.

Good luck sorting it out either way.
01/01/2000 00:00:00 UTC
Frederik said :-
Hi!

I am ordering a replacement clutch basket today. I am naturally responsible of everything I do with my bike, so you don't need to worry about that :-)
Thank you, I simply wanted to know if the sound had some similarity to what you heard, as several others on the facebook group: Honda CBF125 owners group, have also said that they recognized the sound, so the fact you're saying the same only backs it up, which was my goal with this post.

I appreciate your time to reply to me!
Cheers, Frederik
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
I hope it goes OK then. I got a second hand part off Fleabay. The seller assured me it was off a low mileage late model machine blah blah blah... Anyhow whatever the truth mine's fine now.

Let me know how it goes, it's always good to hear.

I'm going to take a grinder to my old clutch basket now out of curiosity and see where the problem lies.
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
I've taken an grinder to the clutch basket and removed the ring gear. I still cannot find one single problem with the ring gear as per the video on youtube. BUT but but but all I can say for sure is that replacing the clutch basket solved the issue.
www.youtube.com/watch?feature=player_embedded&v=AOyg4zF6bwA...
01/01/2000 00:00:00 UTC
Frederik said :-
The replacement part I bought off eBay supposedly has 9900km on it, as my current one is on 29550km now, the new one should last for a good while hopefully.

This issue seems very odd, I can't really get my head around the entire thing that the problem is in the clutch basket, but can't be seen. Very odd. :S
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hi Frederik. I took the disassembled clutch basket to my bike club the other night and several experienced tinkerers had a good look at the pieces. They all agreed there seems to be nothing wrong with it at all. It's maddening to not get to the bottom of this problem.
01/01/2000 00:00:00 UTC
Frederik said :-
Had the mechanic fit the replacement part today, and to my surprise it actually worked! The old one had a crack in it. Thanks for your help!
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hi Frederik. WOHOO!! Thank goodness for that. If you've got the old clutch basket I'd love to see an image of the crack.
01/01/2000 00:00:00 UTC
Frederik said :-
I've attached the image to this post :-)

CBF 125 cracked clutch basket outer ring
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
How the devil did you NOT see that! Yip that's proper knackered that one ain't it. I guess Honda had a bad batch at some point. Alls well that ends well. Cheers for the pic.
01/01/2000 00:00:00 UTC
tahrey said :-
Bloody hell, going to have to see if the XR's crank to clutch gearing is different to that of the CG. I wondered if the noise coming from my exchanged bottom end might be something to do with the clutch (as it's not exactly the strongest or smoothest, probably well overdue for changing) but the relationship between the exhaust beats and the tapping rhythm, as best as I could make it out (using a spectrogram app on my phone) doesn't match up with the 3.33:1 (ie, 10:3) first stage reduction the CG allegedly has... possibly the dirtbike variant is 3:1 (or more likely 3.5~3.6:1) or something like that...

If it's left as-is, would it be likely to fail, or would all the other parts wrapped around it hold the gear ring together despite the crack?
29/10/2018 18:38:58 UTC
Ren - The Ed said :-
The gear ring is taking all the strain from the engine, gearbox and clutch. I cannot really imagine a situation if the ring is cracked that results in a happy ending. Get the clutch off and inspect the ring very closely.


Good call on the spectrogram app on the phone - great diagnosis tool.
29/10/2018 19:01:32 UTC
Ian Soady said :-
Another useful app is an oscilloscope but you need to make up a lead with a couple of resistors (to avoid frying your phone) to plug into the microphone socket.

I can't remember which app I have but there are loads out there.


30/10/2018 10:44:47 UTC
Ren - The Ed said :-
Me... electrical parts... solder... wires... equates to one broken fried phone. It's a great idea and a great use of tech but I'm not knowledgeable enough about elektrikery to be sure I'd not get it wrong
31/10/2018 09:58:55 UTC
Tony said :-
Hi, I'm a bit late to this party but I appear to be in the same boat! Same bike CBF125 2014 14000miles, just bought it for my daughter to do her CBT on.
Runs lovely except for the same fading in and out rattling at less thank crank speed. Good I thought, at least I know what it's likely to be - a cracked clutch basket ring gear.
So out came the rusty spanners (been a biker since I was 16 and I'm now 64!) borrowed a peg spanner for the crank nut, made a locking bar for the clutch drum nut and to pieces it all came - highly expecting to find a crack in the ring gear.
Was I disappointed? Yes, everything looks perfect. Just like yours there is no sign of anything wrong with the clutch basket.
I'm loathe to put it all back together using the same old parts so I'm tempted to just buy and fit another basket and at least have hope that I'm as lucky as you were and the problem is down to poor gear machining leading to premature wear.
What do you reckon - buy a second hand one off Ebay or a new Chinese pattern one?

Your thoughts would be welcome.
Tony

14/12/2020 22:25:38 UTC
Ren - The Ed¹ said :-
The main thing that helped me decide was spinning the motor with the drill and still hearing the noise. But yeah, maddening when you can't actually physically SEE the problem. In a perfect world you'd borrow one to confirm the diagnosis.

Personally I'd replace it. But... cheap Chinese or used Honda? Both come with risks. I'll go have a look at Ebay.
15/12/2020 13:43:08 UTC
Ren - The Ed¹ said :-
Genuine Honda from a Honda dealer - £311.47 - ouch.

Plenty pattern parts on Ebay around the 50 to 60 quid mark. Used about 40 to 50. To be honest I think I'd try the pattern parts but that's your call.

Another option is to get one from an actual real breakers if you can, a shop that you walk into. That way if the replacement is knackered you have a much better chance of getting a refund.

Good luck Tony and let us know how you get on.
15/12/2020 13:49:40 UTC
Tony said :-
Hi Ren, thanks for replying, I suppose the gen Honda one will be made in India like the originally fitted part and probably prone to the same problem - so the excess cost rules that out!

Second hand Honda part from a breaker = £30, new pattern part from a UK seller whose supplied a few and quotes "High Quality" = £45.
I've gone for the £45 option and it's in the post to me.

One thing I have noticed on my original part is that the shock absorber springs don't actually do anything for the first 5 degrees or so of moving the ring gear (by hand), I would have thought there would be a bit of preload on them to prevent any backlash.
It had been standing for 6 months and the motor ran slightly rough when I first started it up but the rattling got less pronounced as it warmed up but still erratic and not at engine speed, perhaps backlash could be causing the rattling and I wouldn't be surprised if the drop of old fuel in the tank has gone off making it run a bit lumpy at first.

When I've got it back together I'll try it on the same old fuel first so that I'm comparing eggs with eggs.
Then I'll put some new fuel in and see what difference it makes.

(Back in the early 90s I had a Honda VFR 750 that I garaged for 4 months over one winter, when I got it out - after 5 minutes running it was down to 2 cylinders and sounded like a bag of spanners, drained the tank and float bowls, put fresh fuel in and it was back to normal).

Oil filter screen was overdue for a clean and the gear selector shaft spring felt a bit weak and lazy so that's getting replaced as well whilst I'm in there.

I'll update you when it's back together.

Regards
Tony


15/12/2020 20:28:34 UTC
Ian Soady said :-
"(Back in the early 90s I had a Honda VFR 750 that I garaged for 4 months over one winter, when I got it out - after 5 minutes running it was down to 2 cylinders and sounded like a bag of spanners, drained the tank and float bowls, put fresh fuel in and it was back to normal)."

Of course if that happened now everybody would tell you it was ethanol!
16/12/2020 11:19:20 UTC
Tony said :-
True, and it's probably going to be a bigger problem when E10 is introduced next year.
16/12/2020 21:25:42 UTC
Ren - The Ed¹ said :-
I imagine your later model 2014 CBF125 was made in Thailand Tony. If memory serves only the earlier versions were made in India. It seems to have no bearing on quality though. A part made in India, USA, China, UK or Japan is only as good as the materials and care that were put into it.

Fresh fuel won't do any harm that's for sure. Any moment now Upt' will be telling us he's filled his BeaST with fuel stabiliser for the winter storage.
17/12/2020 09:17:46 UTC
Ian Soady said :-
Tony - I was actually pointing out that this sort of problem long predated ethanol, and that many of the issues laid at its door have nothing to do with it.

I've never had a problem with petrol left in bikes for 6 months or so - if they don't start first (or occasionally second) kick there's something wrong with them.
17/12/2020 10:13:15 UTC
Upt'North said :-
I'm saying nowt, so there,
Upt'

17/12/2020 10:29:00 UTC
Upt'North said :-
OK, I will.
There has been much nonsense spoken by many, including me, on the subject of over wintering and storage of ICE's.
There has also been a great deal of in depth research by cleverer people into the effects of bio fuel in old fashioned petrol.
If you research, flame fronts, water absorption, flame roundness etc, you can easily read how bio fuel additives and after market Stabilisers effect the petrol in our motorcycles.
For me it's simple....just like me....the bike weighs a third of a tonne and I'm not pushing it.
On the issue of fuel many also regard more expensive petrol a waste of money, but explain this too me. How can a fuel which is a waste of money, reduce the exhaust emissions, provide better mpg and noticeably effect the smoothness of an engine?
I should have said nowt.
Upt'North.
17/12/2020 10:44:46 UTC
Upt'North said :-
Before you ask, Er'Indoors wont/can't push the BeaST either.
Upt'
17/12/2020 10:48:00 UTC
Ian Soady said :-
Yes you should.......

But then perhaps so should I.
17/12/2020 12:10:31 UTC
ROD said :-
I have only had a fuel problem once. This was when I parked the GTR1000 up for the winter and used a 250 Suzuki.
The bike started OK in the Spring, but would not run smoothly and would go onto 2 cylinders.
When I stripped the carbs (all day job) I found a thick green paste around the main jets and the float bowls.
Once the carbs were cleaned the bike ran fine. I have not taken a bike off the road since, and even if I am not using the bike on a regular basis I will give it a run once a month through the winter.
17/12/2020 12:56:22 UTC
Tony said :-
"Ren - The Ed¹ said :-
I imagine your later model 2014 CBF125 was made in Thailand Tony. If memory serves only the earlier versions were made in India. It seems to have no bearing on quality though. A part made in India, USA, China, UK or Japan is only as good as the materials and care that were put into it."

Hi Ren, sorry, I typo'd, my bike is actually a 2012, so where in the world was that made then?

My thoughts on the old fuel issue are - If it won't run correctly on the fuel left in the tank and the only thing that you change is the fuel and it then behaves itself - then it was "the old fuel problem".

I used to ride pre'65 trials on a 1959 Greeves Scottish, if the bike wasn't used for a month or so between trials it couldn't be started without first draining the float bowl. But that's a different issue 'cos it was a pre-mix 2 stroke and we all know what they're like when left standing.
614243...
17/12/2020 19:18:13 UTC
Tony said :-
Greeves Scottish 1959, in case you didn't know what one was!
Posted Image
17/12/2020 19:56:31 UTC
Ren - The Ed¹ said :-
I don't know the exact time when production of the CBF125 moved from India to Thailand. On the frame tube next to the exhaust pipe there's the VIN plate. Mine states something like Honda India on it, see what yours says if you're interested.

A certain Mr Soady of this parish used to ride trials on old school bikes like that. I'm sure that image will tweak some memories for him. I admire, even envy the simplicity of these machines. No panels to faff around with, everything there with easy access and it's all mechanical, tactile and logical. And yet the thought of bouncing up the side of a slippery quarry with those front forks, aye carrumba!
18/12/2020 10:20:22 UTC
Ian Soady said :-
Yebbut mine was a proper bike......

Very nice Greeves though. My uncle used to ride one with some success in the 1960s.


Posted Image
18/12/2020 14:31:07 UTC
Ross said :-
Nice bike, Tony, brings a tear to the eye of a former Essex boy!

Don't get too attached to the bike, Ren, you do realise it's a...two stroke!! Those forks do look odd but Greeves did all right at trials, motocross (scrambling as it used to be known)and road racing with 'em, they sort of became Greeves' USP.
18/12/2020 14:54:53 UTC
Tony said :-
"Ian Soady said :-
Yebbut mine was a proper bike......"

Aha, a Royal Enfield Bullet trials, proper bike indeed.

My '51 530 Bullet, restored in the late 80s, sadly I don't still have it (as with a lot of my bikes). This one went when I got divorced.
Posted Image
18/12/2020 16:45:41 UTC
Tony said :-
Not a 530 - a 350, fingers not working!
18/12/2020 16:46:58 UTC
Tony said :-
"Ren - The Ed¹ said :-
I don't know the exact time when production of the CBF125 moved from India to Thailand. On the frame tube next to the exhaust pipe there's the VIN plate. Mine states something like Honda India on it, see what yours says if you're interested."

Thanks, I'd not thought to look at the VIN plate, so mine's made in India too.
Just waiting for the new (pattern) clutch basket to arrive and I can get it back together.
18/12/2020 19:20:10 UTC
nab301 said :-
On the subject of stale petrol , in the 70's as a young lad.. I used to spend a lot of time in spring proving to neighbours that their hard to start lawnmowers could be cured by replacing the petrol. They would start and continue running if I used a quick squirt of "easy start" but starting from cold was a no no until fresh petrol was added.
Nigel
18/12/2020 22:06:03 UTC
Tony said :-
Hi Ren, and the good news is - I fitted the new pattern clutch basket this afternoon and............ it's all quite - no random rattles, just normal smooth engine sounds.
Just like you, I cant explain it, can't see anything wrong with the old clutch basket.
Thank goodness, going to have a beer now!

Thanks for your great article and the leads it gave me.
Tony.

24/12/2020 16:23:44 UTC
Ren - The Ed¹ said :-
It shall remain a mystery! There's summat amiss but what it is escapes the likes of you and I. Maybe we need the help of a forensic investigator. What matters though is it's reet. Well done squire, is the bike back together and on the road now?
25/12/2020 20:03:36 UTC
Tony said :-
Hi Ren, no it's not on the road yet as I'm giving it the once over for my daughter to ride after she's done her CBT. I'm just glad it's running right now and I can get on with the tittling up!
I should get it on the road in a few weeks and do a dome rides on it - I think I'll quite like it, it reminds me of my TL125 that I bought brand new in 1975 (which is still alive according to DVLA).

All the best
Tony.
25/12/2020 21:39:46 UTC
Upt'North said :-
Is "Tittlin" a dirty word?
26/12/2020 10:26:48 UTC
Ren - The Ed¹ said :-
Only to you Upt', only to you. I imagine he was aiming for "titivating" or perhaps he's a yokel from some unknown part of the UK with words beyond our understanding. In the West Country the four letter word beginning with T that sounds like prat is in fact common parlance. Much to my shock when I was there.

Eeee, you're a good Dad Tony, you spoil that daughter of yours. I don't suppose you fancy adopting a 49 year old from Bolton perchance?
26/12/2020 13:41:59 UTC
Tony said :-
Sorry, didn't mean to offend anyone with the Nottingham slang, I'll go an' get on with me fettlin' in t' jennal.

Can't do it I'm afraid Ren, I've got twin daughters which means if I spoil one I've got to spoil t'other one too and I ain't made o brass thee knows.


26/12/2020 22:12:27 UTC
Ren - The Ed¹ said :-
Gosh darn it!! Story of my life. I guess now I don't need to be nice to you anymore. Pfffft.
26/12/2020 23:14:00 UTC

Post Your Comment Posts/Links Rules

Name

Comment

Add a RELEVANT link (not required)

Upload an image (not required) -

No uploaded image
Real Person Number
Please enter the above number below




Home Ren's Biking Blog

Admin -- -- Service Records Ren's Nerding Blog
KeyperWriter
IO