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

Home Repair And Restoration

CB500X Fork Noise

Job Date 21 January 2023

By Ren Withnell

CLUNK.

If you're not interested in a tale of woe then scroll down to the end for the solution. Otherwise belt up and gird your loins fellow spanner jockeys.

Groing gneer groing CLUNK. Motorcycle forks do make noises but they should be gentle swooshing tones as liquid flows through valves and seals glide along smooth shiny chrome. A quiet rattle from the brake pads is tolerable. Other noises from the front could be wires shaking in headlight shells or loose fitting fairing panels, those kind of rattles. This collection of bangs and grinds are new and disconcerting on the CB500X. 

They started out just occasionally when dismounting and the weight came off the forks. CLUNK. Meh, it'll just be a spring unwinding in the stanchion, be reet. This grew, soon we had hard rattles mixed with heavy clunks when riding.

A wound spring from inside of a motorcycle fork leg
Not typically known for being noisy... but...

It's the front brake. I mean yes, ok, I do remove the spring metal thing that keeps the pads from rattling in the calliper, a slack brake is a happy brake. Sussed, sorted. Ah, wait, hmmm... it makes these noises when I'm getting off the bike with the front brake on. Dammit.

A small section of spring metal cut into a complex shape to prevent brake pads rattling
These stop your pads from rattling. Meh, so what.

It can't be the front mudguard, can it? Well it won't be rattling around when I'm dismounting but maybe it's twisting as the forks extend? I loosen all the bolts, no difference. 

The front mudguard fitted to the CB500X
Nope, snot the mudguard,.

Stiction. This is usually caused when the forks are twisted in the yokes. I loosen the top yoke and the wheel spindle and bounce the front end to get it all settled back into position. I tighten it all back up carefully and set out gleefully into blissful silence. CLUNK! Poop. Clink groink rattle rattle groink. Double poop with cherries on top. 

Argh! I've been at this a couple of weeks now and I'm getting nowhere. I hate hate HATE it when the bike isn't right. Along with this I'm having "personality" issues at work and it is cold, dark, and miserable wintertime. It is easy to remind oneself or anyone else going through a rough patch - "this will pass" but when you're in the thick of it it's very hard to see the light at the end of the tunnel. Hang on in there.

Another miserable weekend's ride in cold air and dark days is frustratingly interrupted with bangs and grinds that bewilder then anger me. I spend an hour lifting and lowering the front end, listening and feeling to find the problem. I remove both fork legs and bounce them individually, no unusual noises at all when removed from the vehicle.

Aha! Head bearings. With the wheel and forks removed the bearings are tight with just a hint of notch in the straight ahead position. They're not bad, but it's GOT to be them, I've checked everything else. £25 sees me with taper rollers rather than ball bearings. 4 nights of hammering and wrenching in the sub zero dark shed and the new bearings are in. My hands look like I've been mining in the Gulag, it'll be worth it though.

The Taper Roller bearing fitted to the lower fork yoke
Tapers - better than balls apparently.

Poop. Damn. Insert your own list of angry, confused, tired and depressive expletives. That's it I'm selling the bleep bleep thing. Bag of woe this piece of excrement. It's a Friday afternoon disaster this one compared to the last one. Why me, why oh why oh why oh why!? I hate my life and I hate this bike. I'm going to get me a pedal cycle.

It's Saturday and I'm at Sharon's with a face like a spanked bottom. The ride down has been punctuated with CLUNK groike clatter rattle. I enlist her help, being fresh to the issue she's all enthusiastic. We both push and pull, bounce and squish, both desperately listening trying to pinpoint the source of the noise. It's the forks, no it's the fairing panels, maybe it's the various pipes and cables?

We both touch and listen, feel and ponder. When up at the handlebars the noise is down there at the forks, definitely. When you get down to the forks the noise is up there, around the headstock, in the fairing panels. ARGH! I spray WD40 to see if anything quiets, nope. I hold and grip, loosen and shake, we both crawl around everywhere and anywhere to find just that right point, that moment, that view that brings enlightenment.

I have a dark and deep sinister concern - cracked frame. With all else eliminated I truly believe it is possible there's a crack in the headstock area. As the presumably correct forks and and bearings take the weight the leverage of the steering angle pulls open the crack. With the weight lifted the crack closes. It's not necessarily the crack making the noise but the movement of panels and parts attached to the frame.

The simple line drawing shows where the crack might be at the headstock of the frame.
Just thinking about this makes me want to puke.

That, well that'd write this bike off. I feel sick at this thought. I bet a frame from Honda would be well over £1,000, then there's the ridiculous amount of work required to transfer the rest of the bike onto the new frame. If I do it myself it'll be viable but is it really viable in a small tin shed in the middle of winter while working full time? Even if it is I'm not going to be riding this bike to Scotland or France anytime soon, that's for sure. 

Frame? The engine is part of the frame. I saw a report on how one CB500X owner had snapped off an engine mount from the engine casings. This thought still makes me feel even more queasy. 

While moving the bike the front left engine mount gives little feedback through my fingers. The right front engine mount gives significant feedback with each clunk and groink. I clean the alloy of the engine to find no sign of a crack. Hmmmmmm... no. Surely not.

This engine bolt is a large Allen bolt supplied by Puig along with the engine protection bar thingies. Sharon sources an 8mm Allen key and with the leverage of a spanner I find this bolt to be tight. Damn. Wait on... I heave and undo the bolt, clean it, blast the area with WD40 and replace the bolt with a firm heave.

A simple line drawing showing the location of the bolt at the front of the engine
This is the location of the bolt in the diagram - on the right side of the engine casing.
Close up of the engine and the mount and the Puig crash bar around the problem bolt
It's in there, under the cap and down the tube of the crash bar.

Silence. 

Wonderful blissful life-revitalising stress-relieving joyfully satisfying SILENCE. 

Here is my thinking. Obviously this bolt was tight but something was moving. Logically this bolt was not tight as in providing a clamping force but tight as in stuck in the threads. As the noise came on gradually I don't believe the bolt has come undone, rather the clamped items (steel frame, alloy engine case and some strange metal spacer) have microscopically worn, allowing JUST a touch of movement that allows more wear and more movement. All the while the bolt never moves in the thread.

I suspect the strange metal washer. With heat cycles from the engine and vibration - if it was say 5.500mm thick it has compressed and/or worn to say 5.485mm, 0.015mm would be sufficient to allow movement. This movement causes everything else to resonate and amplify the noise (blooming faired bikes!). 

We ride with friends for around 50 miles on Sunday. The bike, and my attitude towards the bike and the world, are vastly improved. And breathe. 

I wonder how many other CB500X, CBR500R and CB500F owners have the same issue.


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Reader's Comments

ROD¹ said :-
I think the bike is just complaining about plastic cans for hand guards, cut up jeans for fork protection, and a general lack of cleaning in the only way it can!!
23/01/2023 16:42:22 UTC
Ren - The Ed¹ said :-
It's a fair point well put ROD. If it were all shiny and clean and only used on dry days then this would never have happened. I shall go and chastise myself. I won't change my terrible ways, obviously, but I may choose to feel bad about it.
23/01/2023 16:57:08 UTC
Upt'North ¹ said :-
What sort of site is this, "push, pull, bounce and squish!"
Oh I see.......sorry I was jumping to filthy minded conclusions. It happens.
I'm with Rod, you'll get no sympathy here, you bring it on yourself you naughty boy.
I once had an issue with a crash bung on the CBF1000 that would work loose, it would vibrate like a b...ard when it had undone ever so slightly. Loctite cured the f'in thing.
Well done Ren, but less pushing and pulling please.
Upt'North.
23/01/2023 18:04:32 UTC
nab301 said :-
Quote"I wonder how many other CB500X, CBR500R and CB500F owners have the same issue."
My CBR doesn't have crash bars! but I've been planning to remove the plastics for some deep cleaning of the bits beneath , I guess I'll check the engine mounting bolts too.
Your detective master class reminds me of a noisy wheel bearing in a relatives car many years ago . I travelled willingly in the boot to try and trace which one was the culprit , the 4th bearing I replaced cured the noise ...
Nigel
23/01/2023 20:16:50 UTC
Ren - The Ed¹ said :-
Get your mind out of the gutter Upt'. We were fully clothed and in Sharon's garden in full public view. Oh, wait, that sounds even worse.

nab301 - it's not just me then - phew. Sometimes all we are doing is replacing bits until we find the bit that fixes the issue. It's not exactly scientific but effective, eventually.
24/01/2023 09:21:51 UTC
Ian Soady¹ said :-
You mention that the bolt was supplied with the crash bars and wasn't a Honda item. I suspect that the length of thread is slightly less than needed so that although you tighten it down it's not providing the clamping force it needs. The bits it goes through are most unlikely to have worn unless it was all slightly slack on assembly. And the tolerances on those bits of tube won't be brilliant.

It goes to show that you can't put your faith in torque wrenches. Tighten till it strips than back off half a turn.....
24/01/2023 10:23:54 UTC
Mark said :-
I had a problem with that bolt a few years back. I fitted Givi bars, then came to take them off a year later to get them powder coated and I snapped half of the alloy lug of on the engine. Ended up drilling the lug out and fitting a bolt. Its been fine for about 40,000 miles now.
24/01/2023 21:54:32 UTC
Ren - The Ed¹ said :-
Ouch! That doesn't sound good Mark, I wonder if they're a little "weak". I'm going to make re-torquing these bolts part of my servicing I reckon.
25/01/2023 13:57:37 UTC
Ian Soady¹ said :-
I would be tempted to buy a high tensile bolt to replace the supplied one as it doesn't sound up to the job. There are loads of fastener suppliers around. You could use stainless but I would go for a A4-80 grade which is equivalent to high tensile. And don't forget the anti-seize....
https://www.westfieldfasteners.co.uk/ScrewBolt_M.html...
25/01/2023 14:13:02 UTC
Ren - The Ed¹ said :-
Now *THERE* is a question - what is the correct grade of bolt for an engine mount? I know absolutely nothing about grades and materials and I wouldn't know a mild steel nut from a high tensile one.
25/01/2023 17:02:54 UTC
Upt'North ¹ said :-
You're welcome.
There will be a test......
https://leytonfasteners.co.uk/different-grades-of-high-tensile-bolts/...
25/01/2023 18:46:29 UTC
Ren - The Ed¹ said :-
Now tensile strength is one thing - but - what are the most desirable properties for a engine mount? Does it need to allow a small amount of flex or should it be rigid as possible? I'm imagining a super strong and stiff bolt could be at risk of fracturing under constant flexing and vibrations from the engine and the road.
25/01/2023 20:07:39 UTC
Upt'North ¹ said :-
I thought "High Tensile" meant it was better able to cope with twisting and stretching.
For critical fasteners I would personally take advice from someone more knowledgable than I.
Upt'North.
26/01/2023 09:32:21 UTC
Ian Soady¹ said :-
I probably don't know more than you Upt' - although I did get a distinction for the metallurgy element of my HNC many years ago! What I do know is that all critical fasteners such as engine mountings on my Norton were high tensile EN24(T). All were dull chrome plated originally as stainless wasn't an option. EN24 is easy to machine although that wouldn't be relevant to the current discussion.

Everyone will know that tightening nuts and bolts actually stretches the material slightly and this is what provides the clamping force. The friction between the thread faces gives the resistance to loosening and in a well designed application there should be no need for locking compounts such as loctite.
https://www.westyorkssteel.com/blog/en24-steel-information-strength-in-steel-for...
26/01/2023 10:12:55 UTC
Ross said :-
There's been quite a few reports on the owners forum of crash bars causing problems on 500X's, often excessive vibration. Some have reported problems with the frame twisting slightly out of alignment when the engine mounting bolts have been removed to fit the 'bars and had a struggle to get to all line up again! There's a current thread in the 'ride reports' section which discusses a broken bolt. I believe the official Honda 'bar doesn't use these mounting points, which might suggest something!?
30/01/2023 14:47:11 UTC
Mark said :-
Can't remember if I fitted the bolts that came with the bars or the original Honda bolts.
I did get a few vibes at first but a couple of rounds of loosening everything then retorquing sorted it
The left hand lower bolt did come loose a few times (funnily enough the vibes stopped when it was loose) but I haven't touched them for a few 10,000's miles.
Might give it a good strip down soon as head bearings need doing and might have a look at the valves.
I have got new toy that will probably be used a lot - Vstrom 250 :)
10/02/2023 10:32:40 UTC
Ren - The Ed¹ said :-
With my engine bars the original Honda bolt wouldn't fit down deem inside the tube - hence the replacement from Puig.

As Ross stated there's a few folks coming across vibration issues particularly with aftermarket engine bars. It becomes evident this whole subject is phenomenally complex. Some get the vibes, some don't, some can fix it with a re-torque, others not. When it gets this complex unless you're a professor of vehicular resonance and have access to a team of scientists and equipment, we normal folks can only "suck it n see".

Enjoy the Wee-Strom!
10/02/2023 18:57:31 UTC

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