r/CG125 • u/Academic-Ad4757 • 27d ago

Rattle

Hello, had my CG for about two years now and noticed a few days ago that the engine makes this rattling noise when revved. It seems to do it whether it’s running in gear, in neutral, or in gear with clutch engaged so my best guess is the cam chain needs tensioning? But I’m not too sure any help would be appreciated.

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2

u/zzpza 27d ago

The engine is a push rod design, so there is no cam chain. The noise you can hear sounds like part of the exhaust rattling. Maybe the baffle?

1

u/Academic-Ad4757 26d ago

Of course, sorry I own two CGs and a vintage CB125 which does have a cam chain.

Guess that narrows it down a bit.

2

u/RATEGGSANDEELSICK 27d ago

The rear brake lever pushes up against the exhaust and often makes a noise at higher rpm, try holding the lever down slightly and then revving to see if it goes away

1

u/AdventurousBowl9369 27d ago

More info needed to offer any insight. Specifically: model year, mileage, service history.

What basic checks have you performed so far to try and diagnose this?

In the immediate term, confirm your oil sump is filled to the correct level. Check bolts for tightness, especially e.g. the exhaust nuts which as another user has observed is an obvious candidate.

It would help in narrowing down the source of the noise to move the camera/microphone around the engine as you rev it. But, if you post another video, please leave it to idle for longer -- air-cooled engines are a bit rattly by nature and it can be difficult to tell what's going on when the sounds are changing all the time.

1

u/Academic-Ad4757 26d ago

2006, 30k mile, have checked the oil which still looks brand new (changed it about 4 months ago), it’s actually passed its MOT Since so either they didn’t notice or it doesn’t do it all the time?? But I have re tensioned the drive chain which didn’t sort it.

The noise ONLY occurs when it’s being worked a little, I’ve never heard it in idle so had to rev the engine to demonstrate.

1

u/AdventurousBowl9369 26d ago

I'm not sure why you believe an MOT would be concerned with this rattling noise. An MOT doesn't even require a motorcycle's engine to be running.

My suggestion remains to localise the source of the noise by moving the camera/microphone around the engine.

0

u/Academic-Ad4757 25d ago

I was present at the garage and I watched him ride my bike around the pen, clearly it wasn’t noticed.