Sym Mio (50cc) transmition rattling sound By vacious (Read 4,595 times)

[vacious]

Hi all,

I recently bought my first scooter, a 2010 Sym Mio 50cc.  It seems to run well except for a rattling sound that appears to be getting worse and seems transmission related - Some info :

• Idle to 40km/h - Everything seems fine, no strange sounds.
  
• 40km/h to 45km/h - At 40 km/h i hear a slightly caustic rubbing sound begin, it sounds like something in the transmission is starting to rotate and is rubbing against another component.
  
• 45kmh to 55km/h  - The rubbing sound gradually turns into more of a rattling/ringing sound (imagine shaking an empty glass bottle with a small nail inside).
• 55km/h - 60 km/h - No strange sounds, (wild guess, but feels as if centrifugal force from fast rotation has stopped the rattling).

Do these symptoms give any indication of the cause?

Any help greatly Appreciated!

Ben

[cyborg]

I'd put a bet on some thing wrong with the clutch,,, one of the springs popped off it's mount or broke and a part of it is in there loose or one of the clutch pad arms is loose or broken

[vacious]

Thanks Cyborg! This'll give me the courage to take it apart and start investigating : )

Will post back once i know more.

[cyborg]

Take your time get some baggies for the hardware,,, label everything and take pics as you go,,, if you have to order parts this will help with reassembly later if it has to sit for awhile waiting for parts

[cyborg]

Any progress on the repair?

[vacious]

Please excuse the ridiculously long time to reply!

No progress - Took it to a garage, he checked the clutch and it seems fine, thought it was the variator (which seems a bit loose on the cam-shaft), replaced the variator but the rattling persists. 

Some more info :

• Rattling starts at 40kmh and stops at just over 50 km/h (seems its linked to the rotation of something as the speed of the rattle increases between these two speeds until it eventually fades out at just over 50km/h.
• Rattling definately sounds like its coming from the drive area of the bike (rear end, left side)
  
• No rattling noise when the scooter is revved on the stand - only when ridden
  
• Very strange, but important, rattling noise is not present (or very quiet) when the road is wet, only in dry conditions

It seems to be getting louder and i've done a few thousand km with it like this (driving me mad)

Any ideas appreciated!

[cyborg]

check the rear wheel,,,and surrounding area

[Alleyoop]

I would check the Variator weights if worn or the Guides worn they will make a rattling noise. That would explain why it only happens at certain rpms and once there is enough centrifugal force to overcome the worn part the rattling gets quieter or goes away.
Alleyoop

[cyborg]

but it goes away when its wet

[Alleyoop]

Wet means lubrication

[cyborg]

Yes I know,,,, water getting into the case where the clutch and variator live?

[Alleyoop]

Yep, doesn't take much, pretty big air inlet in the cvt cover. Just the moisture in the air is enough to get things a little damp.

[vacious]

The noise is definitely metallic in sound and not linked to engine rpm (it fades only when the speed is reduced, not the engine rpm). Variator has been replaced with no impact on the noise.


Air moisture idea is interesting - Seems strange that moisture in the air would have such a big impact on the noise, but i cant come up with any better ideas. But which component to check?

If its not moisture in the air causing the reduction in noise, then the cause would have to be the tyre or something else that get immediately wet upon riding on a wet surface. Very odd

[vacious]

cyborg - I've checked the rear wheel and cant see anything obvious - Fact that the rattling does not occur when the scooter is revved on the stand (only when riding) makes it really hard to locate though.

[Guitarman]

Check your rear brakes. You might have a broken pad that's hanging and rubs when your moving. The faster you go it would get slammed off to one side and stop until you slow down again. Seen this happen on mine. Plus the brakes themselves might be loose.