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I have a 125cc scooter, and i also have a simple tachometer from ebay.
After the engine is warm, i noticed that sometimes the engine idle rpm could be 1500, and then after riding a while and
stopping again, the idle could be around 1740.
Then after more riding and then stopping, the idle may go back to 1600 or 1500.
What ever the idle is at a given moment, it stays steady.

I don't know how accurate this tachometer, but you can also notice the change of the engine
sound when the rpm is lower or higher.

Is it ok for the idle rpm to play between that range, or should it be exactly at 1500 or 1700.

Thank you.

Hi,

My scooter is a SYM brand, 125cc.
I have it about 7 years, now with 83000 KM on it.

I don't see any picture...

The 750 x 19.5 x 28 belt will fit because this is the size of the original SYM belt for this scooter.

The problem, it's hard to find this size belt.

So i thought maybe to put a 759 x 20.1 x 30 belt.
Do you think it will be too loose?

The scooter is a SYM brand.

So i tried to lean the mixture (turned the mixture screw Clockwise almost 1/2 a turn),
but it's the same.
More than 1/2 Clockwise, and the engine start to sound not good.

So i guess this is how this scooter. i read that there are scooters that need
a little throttle when starting.

About the idle RPM, is 1700-1800 ok for 125cc motor?

Thank you.

If i'll lean the mixture, what will happen when the engine is completely cold?
Should it start without throttle?

Now when it's completely cold, i also have to give a little throttle.

The valves were checked.

Thank you.

ok, i'll try and see.

What are the symptoms of lean or rich mixture?

If the engine RPM going up good, but the engine power feel a little low,
is it a rich or lean mixture?


Thank you.