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Vibration at specific RPM bands

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liverpool_f_
the 900
the 900

Posts : 368

Vibration at specific RPM bands

Post by liverpool_f_ on Mon 16 Mar 2015, 11:51 am

Hello all,

I guess the only good thing about bike troubles is that I get to talk to you lot again! Anyway, I have had my CB for about a year now and the more I ride it the more I think that the pronounced vibration between 5k and 7k is really more than should be expected. Above and below those revs it is super smooth but it really does vibrate your nuts off in that band.

A bit more info about my bike, it is high miles at 58k (high by bike standards, not cb standards) and has not been particularly well loved over it's later life until now. It has had a full service over the past year and my mechanic said the valve clearances were "close enough to spec." I guess that could mean a number of things. The vibes are rpm specific and not speed specific. It is a later S model if that makes any difference. 

Is there anything I should be looking at to smooth it out or is everyone elses experiences the same? Should a bit of roughness be expected of an older bike? When I ride the Mrs' XL650 it keeps reminding me how bad that vibration is on my bike. 

Any suggestions would be muchly appreciated. 

Cheers guys
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stormbringer
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Location : Aarhus, Denmark

Re: Vibration at specific RPM bands

Post by stormbringer on Mon 16 Mar 2015, 12:40 pm

I've had mine do something similar at mway speed - particularly when just following traffic. Coasting and pulling hard were not at all affected.

I learnt it had something to do with chain tension. A minor adjustment moved the vibe 'out of band'.

Your bike may differ.
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liverpool_f_
the 900
the 900

Posts : 368

Re: Vibration at specific RPM bands

Post by liverpool_f_ on Mon 16 Mar 2015, 12:54 pm

Hi Stormbringer,

I assume you mean the rear drive chain rather than cam chain? My chain and sprocket have recently been replaced and the problem was unaffected. I was actually considering the cam chain as a potential source. Is that likely to be a culprit for a problem like that? I have never seen a service interval for cam chain or tensioner replacement. Would you consider them to last the life of the bike or at 60k miles is it worth replacing them?
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stormbringer
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Location : Aarhus, Denmark

Re: Vibration at specific RPM bands

Post by stormbringer on Mon 16 Mar 2015, 3:02 pm

Cam chain tensioner is known to go bad. Whether this has happened is fairly easy to detect. Take it out and examine it by hand. If the spring is ok, it hasn't gone all bad yet. They do get worn though, so you may still experience a 'loose-chain'-sound, particularly when cold starting the bike.

Cam chains do not seem to wear noticeably, I've been told.

Have you checked the various engine mounting bolts, exhaust mounting bolts etc - including the centerstand mounting?

Another thing to do would be to let another CB500-owner take the bike for a spin and hear if he thinks the bike is too vibey. One of the words that spring to mind when you ask the crowd (yes, we've done that earlier) to describe their bike in one word is 'agricultural'. Another would be 'utilitarian'. Or 'fun'. What I'm trying to say is that you might have expectations that don't match the bike's very direct (soft cushioning is waaay overrated!) behaviour. Why not do the simple check? All it takes is a mate with a CB500.
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liverpool_f_
the 900
the 900

Posts : 368

Re: Vibration at specific RPM bands

Post by liverpool_f_ on Tue 17 Mar 2015, 12:25 pm

Cheers for the advice,

Engine mounting bolts are next on the agenda but exhaust and stand mounts had slipped my mind so I will do a fairly comprehensive nut and bolt check. As for a fellow CB owner, I don't know any but I am sure someone on here wouldn't mind taking it for a rip if I meet any on a rideout or the like. I will have to keep my eyes open for events on the forum!
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Beresford
the 900
the 900

Posts : 1451
Location : not that far from Kirkistown

Re: Vibration at specific RPM bands

Post by Beresford on Tue 17 Mar 2015, 12:38 pm

It can't hurt to check all those items. My bike had an intensly annoying buzzing rattle that I could hear at speed, even over the revs , wind noise and muffling by my helmet.
It turned out to be the RHS mirror glass vibrating in the headshell. Odd that there was no blurring, so I hadn't thought of it as a cause.
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stormbringer
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Location : Aarhus, Denmark

Re: Vibration at specific RPM bands

Post by stormbringer on Tue 17 Mar 2015, 12:44 pm

@liverpool_f_ wrote: I am sure someone on here wouldn't mind taking it for a rip if I meet any on a rideout or the like. I will have to keep my eyes open for events on the forum!

Hmmm. Your location says 'Japan'???
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liverpool_f_
the 900
the 900

Posts : 368

Re: Vibration at specific RPM bands

Post by liverpool_f_ on Thu 19 Mar 2015, 11:32 pm

I am in the UK. I think I clicked whichever flag came to hand first when I found the forum and wanted to get posting. My bike is from Japan though...
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stormbringer
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Re: Vibration at specific RPM bands

Post by stormbringer on Fri 20 Mar 2015, 5:44 am

@liverpool_f_ wrote: My bike is from Japan though...

Sure? - many of the CB's are actually made in Italy. I believe that only the early ones are proper japanese Smile

 Not that it matters much; Japanese QA must have overseen production in Italy too, because they're all well made.

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