Yiben 125cc scooter (Chinese gy6) rear wheel spins when idle

[Randal1991]

Hello my scooter yiben 125cc Chinese scooter when it on its stand in idle the rear wheel spins quite fast until it's warmed up. but then still spins when warm and then I take it off the stand and sit on the bike the bike shakes quite bad. when I move the bike backwards there's a tight spot don't no if that's my problem other than that the bike rides fine just this shaking part at lights drive me mad thanks if any can identify the problem

[Rogerborg]

I'd hazard a guess that it's it's idling too fast, or some genius has dicked with the variator rollers because racebike.

You'll get more help if you tell us more about the bike, like its age, condition, what maintenance (if any) you've done on it, whether you're the first owner, and how red a powerband you've fitted.
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[Randal1991]

The bike is a yiben meiduc 2007 I brought it about 4 months ago it's only had one owner and I have got 2 service receipt from 2008 and 2009. since I purchase the bike its always shaked and rear wheel goes round when in idle but now seams to be getting worse. All I have done is changed the carb to see if that was the problem but still hasn't helped so you think it the idle and mixture screw

[wr6133]

Could be a number of things. First thing to do though is set the carb up properly, just Google "gy6 125cc carb settings" or something similar as you have changed the carb you need to know that is set up correctly (stock) before you go tinkering with other things. My 80cc GY6 has a similar issue that I think is actually knackered clutch springs (5 years old, 13k miles and meant for the original 50cc lump), I just live with it other than stuttering a bit at take off it doesn't bother me.

[Rogerborg]

[Andy_Pagin]

It could just be idiling too fast. The way these things work is you have a pulley continually turning a drive belt that runs around a cleverly designed variable diameter spring loaded pulley on the rear wheel. Above a certain speed the belt clamps to the pulley and the rear wheel turns. As you vary the throttle input the pulley diameter changes so you get a lower ratio under acceleration.

Anyway if adjusting the idle speed doesn't help then you'll need to take off the driver belt/pulley cover and check those bits for wear or damage.

IIRC drive belts only have a guaranteed working life of about 4000-8000 miles.
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[Randal1991]

I set up the carb via YouTube bike sound better but wheel still moves and the lower the idle the more the bike shakes. so I went to andy pagin approach I took the side cover off and noticed the belt as been smashing the top and bottom of the case that was making a weird clicking sound while idling. in the process of taking the belt of and putting it back on I snapped the fan pulley because of the variator nut I haven't got a air compression gun anyways I decided to walk it to the garage to use there compression gun and buy a new fan pulley put it all back together and I ask the bloke at the garage about me wheel moving while idling and he says it's an automatic clutch the wheel should go round in idle I told him me mate got a brand new sym jet 4 and is don't is reply was because mine is old is that true

[andyscooter]

how fast does the wheel turn now

a bit of turning is ok should be able to hold it with a toe on it to stop it

if the scooter moves when on the ground without throttle then the scooter is idleing too fast
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[Iain.]

[evoboy]

I would also go with the clutch springs being worn. It is far easier to replace the whole clutch than mess around swapping new springs in.

The gearbox pulley system on a scooter is bolted directly to the crankshaft. If the engine turns, the gearbox also turns. Once the engine is turning the gearbox fast enough it fires the clutch springs out and engages drive to the rear wheel through a final drive reduction gearbox.

Although, it is not uncommon for alot of chinese built scooters to have wildly high idle speeds. GY6 engines seem to come set with an idle speed of about 3000rpm.
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[Iain.]