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Engine vibration issue

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alanp
Rossi
Rossi

Posts : 53
Location : Norfolk, UK

Engine vibration issue

Post by alanp on Wed 05 Jul 2017, 4:25 pm

Hi all

I posted last year about trying to reduce the very annoying high-frequency vibrations on my CB500. The bars, pegs and tank got a real buzz - a harsh buzz - on from about 5k rpm upwards.

In the course of trying to sort this, and through general maintenance, I did and checked just about everything possible:

  • Every bolt and fastner checked with a torque wrench.
  • The infamous front engine mount freed off, replaced, torqued.
  • New rubber pads to mount seat and tank.
  • Chain adjustment checked, wheel alignment checked.
  • Tyres refitted and balanced.
  • Full fluid and filter changes.
  • Carbs balanced.
  • Valve shims checked and adjusted.

At the time I posted a 'hurray' because I felt that I had made an improvement. However, a bit more riding afterwards left me not so sure...

And today, I got my 'backup' CB500 out of the garage to get it MOT'ed. It's the first time I've ridden it for 2+ years. It is sooo much smoother than the other one - sure there is some parallel twin 'character' going on, but nothing like the hand, foot and finger numbing vibes of the main bike.

Just wondering what else might be going on? The only slight niggle from the overhaul I gave the bike was the cam timing marks, which I couldn't get to align perfectly - but they were only just a shade off - not as much as a link on the cam chain so there was nothing I could do about it.

Any thoughts welcomed - such a shame I can't seem to get this nailed. It's my third CB500 and is definitely the odd one out.
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Grarea
Laser Shark
Laser Shark

Posts : 192
Location : Cornwall

Re: Engine vibration issue

Post by Grarea on Wed 05 Jul 2017, 6:20 pm

I don't have an answer, but I am glad you have posted this.
I had similar to this and gradually improved it.
Then suddenly, one day, it came back.
Like you say, a high pitched buzz.
It was ok on the way out and there on the way back. It is engine related as it is same as you i think, 5k revs up.
I need to lift my feet off the pegs.
You feel it in the bars and the mirrors are blurred.
I need to get onto it. I shall follow with interest.
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alanp
Rossi
Rossi

Posts : 53
Location : Norfolk, UK

Re: Engine vibration issue

Post by alanp on Wed 05 Jul 2017, 9:33 pm

The only other thing I wonder is if these engines have a balancer shaft, and if it has any adjustment?
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Beresford
the 900
the 900

Posts : 1431
Location : not that far from Kirkistown

Re: Engine vibration issue

Post by Beresford on Wed 05 Jul 2017, 11:21 pm

alanp wrote:The only other thing I wonder is if these engines have a balancer shaft,  and if it has any adjustment?



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ANDYC
the 900
the 900

Mechanic
Posts : 751
Location : Windsor

Re: Engine vibration issue

Post by ANDYC on Thu 06 Jul 2017, 9:40 am

It does have a balancer shaft but no adjustment.
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Vardypeeps
Two Tone
Two Tone

Posts : 125

Re: Engine vibration issue

Post by Vardypeeps on Thu 06 Jul 2017, 12:32 pm

I get a buzzing from the left underseat plastic cover at higher revs poss just over 5k.

Could it be where the covers slide into the rear fairing, the lugs on mine have worn over time and now rattle producing a harsh buzz. Looking to pack it with some double sided foam tape or similar.

Only thing I can suggest other than the usual fitting of aftermarket cans seems to make the CB500 buzzy too.
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alanp
Rossi
Rossi

Posts : 53
Location : Norfolk, UK

Re: Engine vibration issue

Post by alanp on Thu 06 Jul 2017, 8:41 pm

Many thanks. Mine isn't bodywork related,  it's definitely engine vibration / harshness. But a good suggestion,  thanks.

With the balancer shaft, I wonder if those springs and/or nut could work loose or wear?
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alanp
Rossi
Rossi

Posts : 53
Location : Norfolk, UK

Re: Engine vibration issue

Post by alanp on Fri 07 Jul 2017, 8:05 pm

Ok, found some time to study the manual. There are alignment marks for the balancer shaft, so at the next oil change I'll whip the cover off and have a good poke around. Might be a month or so, but I'll report back...
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Jameshambleton
Moderator
Moderator

Posts : 1809
Location : Bedale, North Yorkshire

Re: Engine vibration issue

Post by Jameshambleton on Sat 08 Jul 2017, 3:09 pm

The balancer shown in the photo in Beresford's post is cog driven differently from the crank. It does require taking the clutch cover off to access it, though if you mess up the marks then your crank WILL hit your balance shaft and well you don't want that. 

IRRC the cogs will only link in with eachother in a set position but I'm not 100% sure on that.

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