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'Clonk' noise when bike switches off?

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Az
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PostPosted: 21:40 - 07 May 2013    Post subject: 'Clonk' noise when bike switches off? Reply with quote
I've always wondered why my bike makes a like 'clonk' noise when it switches off, does anyone know why motorcycles make that noise when switched off?

Thanks in advance, Az Smile
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Walloper
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PostPosted: 21:59 - 07 May 2013    Post subject: Re: 'Clonk' noise when bike switches off? Reply with quote
HondaAz wrote:
I've always wondered why my bike makes a like 'clonk' noise when it switches off, does anyone know why motorcycles make that noise when switched off?

Thanks in advance, Az Smile


Main relay disconnecting when you switch off the power. It may even click when you turn on the power.

If it bothers you you could maybe put something under the mounting to cushion it.
Or it may be on the road oot and warning you that the bike is about to explode in a ball of flames as soon as you get it to full chat. Very Happy
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Paddy Blake
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PostPosted: 22:04 - 07 May 2013    Post subject: Reply with quote
I'm not that sure I know what you mean but if it is a single it could be the piston getting to compression and not firing.
The engine sudden stop because it can't get passed the compression stroke when you turn it off.
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Az
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PostPosted: 22:15 - 07 May 2013    Post subject: Reply with quote
it's weird though because it doesn't always make the noise, most of the time it does and it varies in loudness as well, thanks for all your answers as well


I dont think its the piston, does sound like something more electrical

it doesn't make the sound when switched on, just makes the normal electrical tweeky noises Smile
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Walloper
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PostPosted: 22:17 - 07 May 2013    Post subject: Reply with quote
Paddy Blake wrote:
I'm not that sure I know what you mean but if it is a single it could be the piston getting to compression and not firing.
The engine sudden stop because it can't get passed the compression stroke when you turn it off.


The crank's momentum will carry the piston past TDC so that rules out that theory.

And anyway, it would be meeting a cushion of air so wouldn't exactly clunk.
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Walloper
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PostPosted: 22:41 - 07 May 2013    Post subject: Reply with quote
HondaAz wrote:
it's weird though because it doesn't always make the noise, most of the time it does and it varies in loudness as well, thanks for all your answers as well


I dont think its the piston, does sound like something more electrical

it doesn't make the sound when switched on, just makes the normal electrical tweeky noises Smile


The electrical 'tweeky' (how technical Smile ) noise is the fuel pump priming the fuel system. More a sort of 'Stuisszt' sound. Possibly a little bit of capacitor whine too. Yinggggggg (quite quietly)....
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Dave_R
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PostPosted: 23:50 - 07 May 2013    Post subject: Reply with quote
This noise?

https://www.youtube.com/watch?feature=player_detailpage&v=Yz6ljcPzY7E#t=164s
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Walloper
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PostPosted: 23:58 - 07 May 2013    Post subject: Reply with quote
Dave_R wrote:
This noise?

https://www.youtube.com/watch?feature=player_detailpage&v=Yz6ljcPzY7E#t=164s


That noise is the rev limiter. What ever is used on that bike is probably fooked.

But the rider is maybe a wee bit too swift around those streets. And it looks like winter roads, cold tyres et al. Tut Tut
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Az
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PostPosted: 00:05 - 08 May 2013    Post subject: Reply with quote
wow that CBF is seriously fuurked on that video lol, i've never experienced any problems like that on mine, only problem ive had with my bike so far (sinse december/4000 miles) is seized links on chain and worn sprockets... what is my fault anyway because i didn't realise how often u had to lube these bastard chains, newbie mistake Smile
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Az
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PostPosted: 00:06 - 08 May 2013    Post subject: Reply with quote
Dave_R wrote:
This noise?

https://www.youtube.com/watch?feature=player_detailpage&v=Yz6ljcPzY7E#t=164s


yeah the noise around 2:45 is the noise i attempted to describe lol

What is that noise???
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Dave_R
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PostPosted: 00:14 - 08 May 2013    Post subject: Reply with quote
Walloper wrote:
Dave_R wrote:
This noise?

https://www.youtube.com/watch?feature=player_detailpage&v=Yz6ljcPzY7E#t=164s


That noise is the rev limiter. What ever is used on that bike is probably fooked.

But the rider is maybe a wee bit too swift around those streets. And it looks like winter roads, cold tyres et al. Tut Tut


I was the rider, I meant the noise at the end of the video at 2:45 when I turned the bike off, I wanted to know if it's that 'clunk' HondaAz was on about - and what that noise actually is! I just happened to have that video handy.

On separate note, couldn't be the rev-limiter because I was no where near the red line, the CBF125's engine sounds hideous at 11k!

Also, the day and bike was anything but cold, probably the hottest day of 2013 so far and the kangaroo hopping (and rev drops) only happens when the bike's engine is hot after a long ride, tyres would deffo have been toasty by then.
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Walloper
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PostPosted: 00:35 - 08 May 2013    Post subject: Reply with quote
Dave_R wrote:
I was the rider, I meant the noise at the end of the video at 2:45 when I turned the bike off, I wanted to know if it's that 'clunk' HondaAz was on about - and what that noise actually is! I just happened to have that video handy.

On separate note, couldn't be the rev-limiter because I was no where near the red line, the CBF125's engine sounds hideous at 11k!

Also, the day and bike was anything but cold, probably the hottest day of 2013 so far and the kangaroo hopping (and rev drops) only happens when the bike's engine is hot.


You won't have to be near the rev limit.
I suggest the rev limiter is fooked so is cutting power before the 'rev' limit.

Heat related could mean the transistor that determines the limit is goosed.

I think the clunk you can hear is the release of the 'drag' on components through the gearbox when you shut off the engine.
Normally if you start up in neutral the rear wheel will spin this will ease off as the oil heats up and there is less oil to transmit that little bit of power drive to the output shaft.
When you switch off the engine then the bit of drag that was resisting the drive from the engine backs up and makes the clunk.

Normal.

I like that bike BTW, cool colour.

Did the dealer fuel pump fix the rev problem?

Still too quick in the town though. Smile

Cherry Blossom. Looks like frost. Embarassed
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Dave_R
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PostPosted: 00:52 - 08 May 2013    Post subject: Reply with quote
That vid was recorded two days ago and I've only spoken to the dealer about it yesterday, reckons it's a fuel pump issue. Now I'm waiting for day to arrange the bike to be recovered to the dealer.

Discussion about the kangarooing here;
https://www.bikechatforums.com/viewtopic.php?t=271032

About the speed, reviewing the footage I figured the fastest I did was 23mph. Is this really too fast?
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Walloper
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PostPosted: 01:24 - 08 May 2013    Post subject: Reply with quote
Dave_R wrote:
That vid was recorded two days ago and I've only spoken to the dealer about it yesterday, reckons it's a fuel pump issue. Now I'm waiting for day to arrange the bike to be recovered to the dealer.

Discussion about the kangarooing here;
https://www.bikechatforums.com/viewtopic.php?t=271032

About the speed, reviewing the footage I figured the fastest I did was 23mph. Is this really too fast?


Nah.. It's probably just the illusion of the wide angle lens that distorts the perspective space and time.
Is it a GoPro or a TARDIS camera you have. Smile

Good luck on the bike fix.

I had the fuel pump fail on my BMW R1200GS. It was a common fault that the pump's integral control circuit burned out in them. AA recovery to BMW at my cost (Well through AA) as the bastart was out of warranty.
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Dave_R
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PostPosted: 01:55 - 08 May 2013    Post subject: Reply with quote
The cam is a Contour ROAM, does the job well, will be posting a vid of some idiot driving in to me soon.
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