CBF1000

CBF1000 => CBF1000 - General Discussion => Topic started by: iNCORRIGIBLE on 30 March, 2019, 08:32:45 AM

Title: A "KLUNK"
Post by: iNCORRIGIBLE on 30 March, 2019, 08:32:45 AM
Hi All.Got a silly one going on on my 2009 Biffer! As soon as I ride over a road bump/hole at over say 30mph bike makes an obvious metallic ,Klunk.Can't see/ feel anything loose. All thoughts most welcome.Thanks,Ed.(Southminster,Essex)  :087:
Title: Re: A "KLUNK"
Post by: Art on 30 March, 2019, 09:00:30 AM
Suspension - Either front or rear suspension stanchion bottoming out.
Drive chain - Chain slack, worn chain slider.
Centre stand - Weak or failed centre stand spring
Side stand - Weak or failed side stand spring (although this should also cause the engine to cut out)
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 30 March, 2019, 09:58:35 AM
Thanks,Art.Will check those four out & report back! Ed. :123: ps sounds/feels like the rear end?
Title: Re: A "KLUNK"
Post by: Art on 30 March, 2019, 10:30:35 AM
Could also be a rear wheel bearing, there are three - two wheel bearings and the cushion drive (rubber damper flange) bearing. Although if these are failing you should notice a twitching at the rear end and it would be an MOT fail.
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 30 March, 2019, 06:47:56 PM
Hi,Art.Forgot to mention that she is only at 11,000 miles.Chain adjustment seems to be a front runner for the noise as I have been adjusting on the centre stand & not the side stand as instructed! Will update you on the outcome.Ed.
Title: Re: A "KLUNK"
Post by: Art on 31 March, 2019, 10:59:48 AM
You can adjust the chain on either the centre stand or the side stand. What's important is that the the front and rear sprockets align with each other and the swinging arm (see drawing) and that chain slack of between 1 and 1.5% of the total chain length (20 to 30mm) is measured at the tightest point.
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 31 March, 2019, 01:23:33 PM
Thanks,Art. I was following the HondaOwner's & Workshop manuals who make definite statements about using the sidestand.Have compared both methods & can't see any difference in the result! Is certainly  easier with the bike on the centrestand.Ed. :001:
Title: Re: A "KLUNK"
Post by: tonywing on 31 March, 2019, 05:18:44 PM
I had a similar problem when I first purchased my 2009 Mk1. I discovered that the previous owner had probably dropped the bike on it's left side and this had resulted in the exhaust being pushed in closer to the bike that it should be. When I went over a bump the exhaust came into contact with the rear axle bolt and over time it had made a dent in the exhaust. The exhaust being pushed in was hardly noticeable. I replaced it with a second hand one off Ebay for £30 and problem solved. :028:
Title: Re: A "KLUNK"
Post by: Liv0704 on 31 March, 2019, 05:48:29 PM
I had a clunk under the same scenario, ended up being a loose motor mount.
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 31 March, 2019, 08:33:03 PM
Many thanks to both Tony & Liv.Have yet to run the old ZimmerBlade over a series of suitable lumps/bumps but will certainly show my findings in a few days.Thanks again Pete. :123:
Title: Re: A "KLUNK"
Post by: john 087 on 01 April, 2019, 10:05:10 PM
I have a mk2 and had the same problem. There was play in the back wheel bearing
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 01 April, 2019, 10:40:32 PM
Thanks,John.Have checked rear bearings & foun
d no perceptible movement. Ed.
Title: Re: A "KLUNK"
Post by: Scott_rider on 02 April, 2019, 07:15:15 AM
Might be a loose headstock? Check the tightness of the nut on the top yoke, underneath the handlebars. You can just about get a spanner on it without taking the bars off. If itís loose, youíll feel it straightaway, and if so it will cause a dull clunk when you go over bumps. It should be torqued up to the correct setting.
Itís worth checking, mine was loose.
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 02 April, 2019, 07:59:35 PM
Thanks,Scott.Have checked that area & all OK but I have certainly experienced that on other bikes previously.Ed. :123:
Title: Re: A "KLUNK"
Post by: iNCORRIGIBLE on 29 April, 2019, 05:07:56 PM
Thanks All for your help.As Art suggested it turned out to be one of the three rear wheel bearings failing!.Only found minimal play on inspection but bearing was actually badly degraded when I got into it! Thanks again to All.ED.
Title: Re: A "KLUNK"
Post by: Piper on 29 April, 2019, 09:06:13 PM
*Originally Posted by Art [+]
You can adjust the chain on either the centre stand or the side stand. What's important is that the the front and rear sprockets align with each other and the swinging arm (see drawing) and that chain slack of between 1 and 1.5% of the total chain length (20 to 30mm) is measured at the tightest point.
Its not a good idea to adjust on the centre stand if you are only allowing the minimum of 20mm free play. The distance between the front and rear sprockets will be a little shorter when on the centre stand as the swing arm is lower (Its all due to the location of the swing arm bearing being in-between the sprockets). I adjust mine on the centre stand as it is easy to check for the tightest point ensuring that there is at least 25mm free play then check with the wheels in the same position on the side stand to ensure that there is a minimum of 20mm play. It is always slightly less on the side stand. 

My MOT tester gets me to sit on the bike to try and get the 2 sprocket and swing arm centers to line up as much as possible so the chain is at its maximum stretch then he checks that the chain is not over tight. Obviously it doesn't require the same amount of slack in that position.   
Title: Re: A "KLUNK"
Post by: alfau on 30 April, 2019, 09:34:05 AM
Time for me to say hello.
I joined a few days ago motivated by a new to me 2008 cbfa 1000. 49 thousand kilometres on the clock.
Interesting topic "Klunk"
What is scary is the many options as to what it might have been.
Needless to say I have been tracking a klunk of my own which eventually turned out to be the top mounting bolt for the rear shock.
It was quite loose. klunky loose. With the bike on the centre stand I levered the swingarm up and down from under the tyre with a tyre leaver and a block of wood.  it tightened up ok just waiting for  rain to stop.
I found my weak centre stand spring, interesting but wrong noise.
Title: Re: A "KLUNK"
Post by: Art on 30 April, 2019, 11:13:48 AM
*Originally Posted by Piper [+]
Its not a good idea to adjust on the centre stand if you are only allowing the minimum of 20mm free play. The distance between the front and rear sprockets will be a little shorter when on the centre stand as the swing arm is lower (Its all due to the location of the swing arm bearing being in-between the sprockets). I adjust mine on the centre stand as it is easy to check for the tightest point ensuring that there is at least 25mm free play then check with the wheels in the same position on the side stand to ensure that there is a minimum of 20mm play. It is always slightly less on the side stand. 

My MOT tester gets me to sit on the bike to try and get the 2 sprocket and swing arm centers to line up as much as possible so the chain is at its maximum stretch then he checks that the chain is not over tight. Obviously it doesn't require the same amount of slack in that position.

Seems to me we're saying the same thing there. The method I describe above is how I was taught during my apprenticeship. Note too the correct amount of chain slack is determined by the length of the chain length and is calculated as 1 to 1.5% of the total chain length. On a stock CBF1000 that is exactly 1" +/- ⅜" (motorcycle chains remain imperial) or roughly 25mm if you prefer.