50cc cvt belt question 139QMA motor By jeffinchina (Read 603 times)

[jeffinchina]

I have a Chinese scooter that is 50cc ( or maybe 48 or 49cc) and I recently opened it up to inspect the belt. I bought it used from a friend here in China. He bought it new and sold it to me used for $250. He also said he never changed the belt ( as he had no idea there was a belt!).

It just hit 3000k on it - 1000 miles. I figure now is a good time to change the belt that's inside as I remember that 1000 miles is a good time to replace it.

Everywhere I look it says the belt for a Chinese 139QMA motor is 669-18.1 Belt (for GY6 50cc Scooters) but the belt that is installed is 743-20.30

Now the scooter is running FINE so I don't want to change that but I am curious as what to do regarding the belt spec. Unfortunately I can't get REAL Powerlink belts in China ( I have to wait till I go to the USA again or have one shipped here) so I may just use a Chinese belt.

So the question is... What spec belt to use?

Also from the oil perspective. I changed the oil today and used a Castrol 10W30 Motorcycle oil ( not synthetic) only because I couldn't find a 10W40.
The manual is in Chinese and I couldn't make heads or tails out of the oil spec.

The motor code is 139QMA

Suggestions please. Thanks much.

[alleyoop]

A 743-20-30 belt is for a 150cc short case motor, so that belt is way to long for that cvt and it is probably flopping around in there. The correct belt for a 139qmb motor is 669-18.1. 10w30 oil is fine not a big deal.
Alleyoop

[jeffinchina]

I opened the cover and checked the tension and it's snug. Couldn't possibly be flopping as there didn't seem to be any extra belt

[alleyoop]

The belt should be marked with the size take picture of the CVT with the numbers of the belt in the middle so we all can see this. But the belt for that scoot is 669, so you go with what you want just telling you what is the correct belt for that scoot.
Alleyoop

[jeffinchina]

I took it to a scoot shop today in China and through my friend who speaks the local language I had a conversation with the mechanic.

I told him it was noisy coming from inside the belt area at times and maybe the belt was too long and showed him the board spec for a belt -669-18.1 He said he never installs that sized belt on the 50cc models.

Also he said there is a good chance the variator or clutch needs fixing. His prices weren't high - $5 for a chinese belt and about $15 for a new clutch or variator. That includes labor.

But my biggest fear is that if the belt is too long it will break from rubbing.

All in all this scooter does well - hits almost 50mph - and runs smooth. I really don't want to mess it up as I know chinese scoots are temperamental machines

[alleyoop]

only way to tell if the belt is to long is take the cvt cover off and start it up. it its to long it will slap some.
Take a video of it idling with the cvt cover off and we will be able to tell if the belt is to long.
Otherwise we are guessing just like you are.
Alleyoop

[jeffinchina]

So I took it to a scooter shop here in China a few days ago and the mechanic changed the clutch and at my urging changed the drive belt.

I watched him do everything but couldn't see what the specs were on the belt. Looked a little wider than the old belt.

He also tightened the rear wheel a little.

Since this procedure that clanking noise coming from the back has stopped.

Total cost for parts and labor - $26. New clutch unit and new belt. Little 50cc scooter is doing well now ( for a Chinese made scooter that is...).

Thanks again for your input Alleyoop

[lanternscooter]

Aug 23, 2014 3:36:41 GMT -6 jeffinchina said:

So I took it to a scooter shop here in China a few days ago and the mechanic changed the clutch and at my urging changed the drive belt.

I watched him do everything but couldn't see what the specs were on the belt. Looked a little wider than the old belt.

He also tightened the rear wheel a little.

Since this procedure that clanking noise coming from the back has stopped.

Total cost for parts and labor - $26. New clutch unit and new belt. Little 50cc scooter is doing well now ( for a Chinese made scooter that is...).

Thanks again for your input Alleyoop

at least you got it running. around here you couldn't buy the clutch for what you paid total. wish things were that cheap here.