CG 125 (2004) Engine Noises

[Falco]

Hi Guys,

There are actally a couple of questions I wanted to ask about my c 125's engine noise. There is a video of it here:

https://vid.me/I4II

The 1st question is about the general noise. I haven't owned a 125 before so I don't know, but is that normal? It sounds like its clattering a bit to me? I was planning to check the valve clearances tomorrow anyway but I would be interested to know if that is a normal noise for such an engine.

The 2nd question is of a more serious nature.
A couple of weeks ago the side stand snapped and dumped the bike on its side. There was no obvious damage but since I have noticed a sort of buzzing (though I am not sure how obvious it is in the video)? Like a piece of metal vibrating rapidly between 2 hard surfaces. It is most noticeable at high RPMs but it is also there at very low RPMs as well (ie whenever the bike is vibrating a lot).

At first I thought it might be something to do with the petrol tank as holding the tank with my knees muffled the noise. However last week I removed and checked all the mountings on the tank and there was nothing amiss. The noise has changed slightly and now holding the tank makes no difference (so maybe I fixed part of the problem).
When riding it sounds like it is coming from under the seat, but in the video it seems louder near the rear of the bike.

I am at a bit of a loss for where to start looking for problems (I have been round the bike once, checking fasteners and could find nothing loose). Can anyone suggest a/some starting points?

[MCN]

I thought the Brazil bikes came without the side stand but there are stands available on t' Interwebs? Possibly someone has bodged a bit of bar on and that's failed.
The correct stands are very robust. It's not a great idea to fit one as there is no interlock to prevent the bike being driven with the stand deployed. Most modern bike cut the engine if the stand id down and the bike in gear to prevent coming a cropper on a left-hand bend when the stand contacts the ground.
There should still be a bracket/weldment as part of the frame to accept a side stand. There is also provision for the interlock switch too. But that will involve a bit of 'wiring' to connect to the ignition circuit too.

The noise sounds 'normal'. Any doubt in any 'unusual noise from a machine requires an oil drop and filter check. If nowt in the filter then no problem replacing the dropped oil.
The engine has a steel mesh screen as a 'filter'. They are low output engines so not a great need for high performance filtration. But the oil should be changed every 3k miles I think.

Worn Tappets don't make an engine rattle. The misconception is due to some law of mythery.
If you never adjust the tappets then the faces of the valves and seats wear until there is no 'valve clearance' and then there is no air/gas-tight seal. The engine performance will drop due to loss of compression forces.
The valve clearance decreases as the engine wears. So scheduled adjustment actually addresses this wear and opens the gaps again.

You can probably Phaph to this.

https://hondacg125.awardspace.com/index.htm
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[spottedtango]

Yep I agree sounds normal to me, i think CGs usually have a bit extra valve train noise because they are push rod operated (OHV) and have rocker arms instead of shims. Plus its air cooled so no water jacket to dampen down the noises. It also depends how many miles the motor has done too.

You dont have a toolkit with it? Check and see no spanners or anything has tried to escape. It sounds like you've touched on the issue with the tank though. I would try messing around with it to see if its the cause. Check all the other trims like side panels, make sure no lugs have snapped or things like that

[MCN]

Noise:

Do you have L plates fitted? The rear plates can act like a massive resonator and amplify any normal vibration.

Really all you can do is try to set the RPM at the point where it's most vibey and then try to dampen the vibe with your finger or a screwdriver by touching/pressing any and all part of the bike. The bits that stop the noise possibly need packing with something.

Our CG125 has a topbox which vibrates like a bastart at 1/2 revs. (Whateverthefuk 1/2 revs is. )
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[talkToTheHat]

One of the bikes i testrode yesterday was a bit stumbly at 4000 rpm. Suspect that was down to emisions/noise lean spot and the cobwebs needing blowing out. There was, however a bag o' spanners rattle accompanying this. Carefully listeing and the sound was behind me. I stopped, took the seat off, put the tool kit in my pocket and the sound went away. Really was a genuine bag o' spanners.
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Bandit. does. everything.

[Falco]

[MCN]

Sorry I meant by an 'Oil Drop'.
Drain the oil into a clean container (Your Mum's dish bowl) If no issue found and the oil is within the service life then reuse to fill up and top off as required.

Misleading I know as an 'oil drop' could also be 'a drop of oil'. But that would only be on Jamie Oliver/Nigella Lawson's forum.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[WD Forte]

Sounds rough as a bears ass to me
BUT
Having made a vid of one of my bikes once I was horrified at playback and rushed back out listen again thinking it had a terminal condition.

I found the wee mics you get in cams/phones tended to get swamped or exaggerate certain frequencies and not always give reliable results.
I also discovered I tended to get too close and standing say 6 feet away gave a better rendition of what the bike actually sounded like.
the exhaust can sometimes be a bit err 'percussive' and sound like an 'orrible knocking.

Top marks for bothering to make a vid though

My lads 125 has an irritating tinny noise when revved which we traced
to a loose exhaust liner and baffles
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bikers smell of wee

[Falco]

[MCN]

Have a shoofti at the the manual on my 1st post.
It is vital.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[WD Forte]

this one sounds OK
https://www.youtube.com/watch?v=2srLbDyjZe8

note how he lets it tick over OK?
Don't just rev the arse off it as its just bloody awful noise and hard to
listen for any knocks and rattles
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bikers smell of wee

[Falco]

[MCN]

[Falco]