Sym Mio (50cc) transmition rattling sound By vacious (Read 3,915 times)

[vacious]

Thanks Guitarman, was quite hopeful about this brake idea! But unfortunately doesn't seem to be the cause(applying the brakes makes no difference to the noise).

Having listened more, it does seem drive related - It seems to be a rotational noise that increases in frequency with speed, also, it sounds different under acceleration to deceleration.

I'm going to try and record it on my phone if i can get a good enough tailwind to eliminate wind noise

[Alleyoop]

Well it could be the rear wheel bearing or the gears in the tranny, have you checked to make sure the tranny has sufficient oil in it.
Alleyoop

[cyborg]

Thats a real good point alley,,, rear end may be dry,,, or better yet the no noise running on the stand then noisy with a load,,, bad wheel bearing,,, that's where I'd put my bet

[cyborg]

Any luck?

[cyborg]

Find the problem?

[solanocycle]

Yes. Change the gear oil and look for metal. May be in your gearbox. How many miles or kms are in the bike? I assume the tech checked your roller weights and slides on the variator or replaced them? If your variation was loose, that is very very bad if it was run for any period of time, and may have do everything damage to the crank and not let the new variator tighten properly.

[cyborg]

Hey any luck with the rattle???

[solanocycle]

Another common metallic sound is the starter bendix rubbing on the starter gear. Can't remember the setup on the Mio, but if it has a bendix inside the transmission, you can put a small dab of grease on both ends where it fits into the outer and inner case. This sometimes helps quite it down. Just a dab of grease inside the holes, not outside. Don't want it getting on the belt. This would NOT be a rotational sound, however. It would just be a metallic rattle at certain rpms from the vibration of the bike. It is caused from excess play. You could replace the parts, but it is usually nothing to worry about, just annoying. Rotational is usually clutch assembly/gearbox related. But, if your variator was loose, it could still be out of round/damaged on crank.

[vacious]

Thanks for all the ideas!

Finally took it to a mechanic this morning - He drained the gearbox oil and bits of metal came out Doesn't look good.

He's going to take it apart and see if its bearing of gear damage - Either way it looks expensive.

[vacious]

Gearbox taken apart and everything seems fine, no signs of damage - Though there was quite a bit of metal floating around. The mechanic is guessing that this loose metal is shavings from when the threads were originally drilled into gearbox casing in the factory.

I'm not feeling confident that this is the cause though, surely if loose metal was causing noise and vibration it would also cause damage. Also doesn't explain how the noise is subdued in the dry.

Anyway - tomorrow he will clean and reassemble - Will post an update then.

[cyborg]

Good luck!

[vacious]

I've got the scooter back - Gearbox cleaned up and re-oiled but the noise lives on.

Then a bit of a breakthrough, we discovered that if you push the stand down slightly whilst riding, most of the noise disappears - It seems that the stand is resting against the frame (or something else) and amplifying the vibration, all of the metallic ringing sound is coming from the vibration of the stand.

However, the actual vibration is still there, with the stand out of the equation, its a dull, low frequency rotating noise that starts at 40km/h and increases in frequency with the speed of the scooter. It is intense enough to be felt through the floor at higher speeds.

Certainly seems that that gearbox, clutch, variator and belt are not the issue - I'm now wondering whether i should just forget about it - Its been present since i bought the scooter (2nd hand), and i've done 5000km without much increase in the problem (i think).