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Hi,

I have a SYM 125cc scooter, and for about a week i have a strange problem.

I can ride for about 10 minutes and then stop at a traffic light, and the idle speed will be ok at around 1700 rpm,
and it will stay like that. It's not jumping up and down.
Then, i'll ride another few minutes, stop at another traffic light, and the idle speed will be at around 1300-1400 rpm.
again, it will stay like that. It's not jumping up and down.

Sometimes, it can idle at around 1900-2000 rpm.

I checked and looked, and i found a torn hose that goes from the charcoal canister to the air filter hose (that connects to the carburetor).
I fixed that, and looked for other hoses that are cracked or torn, and didn't find anything else that is broken.
I checked that the air/fuel mixture screw is adjusted correctly.

It didn't help. still the same problem.

So i took the carburetor out and i dismantled it, and cleaned everything really good (all the passages and jets).
I also checked the fuel float level, and it is ok. Everything is ok with carburetor.

It didn't help. still the same problem.

While the engine is running, i tried to spray water around the vaccum hoses and the intake manifold, to check for leaks,
but i don't hear a change in the idle speed when doing it.

I don't know what else to check.
A bad spark plug can cause this problem? (I'll try to change it)

Hope someone have an idea what else to check.
Thank you for the help.

The oil consumption is around 120ml of oil every 1000km/600 miles .
The oil capacity is around 900ml.
So it's only around 13% of oil consumption from the entire crankcase oil amount.

Well actually, from what i understand from the user manual of the scooter, the manufacturer recommend to use
a mineral oil, so the manufacturer says to replace oil every 1000KM.
The SYM importer here, recommend to use a semi-synthetic oil, which from what i understand is a mineral oil with additives.
So maybe the semi-synthetic oil has a longer life in the engine, and because of that they recommend an oil change every 4000KM.

Also, where i live, i think nobody will buy a scooter if they knew they will need to change oil every 1000KM.

Hello,

It's been about 3 years since i rebuild the scooter engine, and i thought i'll update you.

Before that, just a quick reminder.
This scooter is a SYM 125cc air cooled.
The scooter reached 115,000 KM (around 71,000 miles) with the original engine.
I decided to do a rebuild since it started to burn a lot of oil.
Here is a link to the post i opened back then:
itistheride.boards.net/thread/7165/sym-125cc-rebuilding-engine (pictures of the rebuild on page 3.)


Anyhow, 3 years later, and i'm now almost at 150,000 KM (about 93000 miles).
Engine working ok.
Oil consumption is now around 120ml (4 oz) every 1000KM (600 miles).
Pretty good.

I hope i'll reach 200K KM on it.

I'll take some pictures of the scooter tomorrow, and i'll upload them.

Hello,

I did an oil change today, so i warmed up the scooter for a few minutes before draining the oil.
After i refilled with new oil, i changed the spark plug with a new one.
I then noticed the color of the old spark plug, and i don't know if it's too lean or too rich.
It's kind of grey/white at the bottom and black at the top. See attached picture.
The scooter run fine, no problems.
Is it like that because i ran the cold engine for only a few minutes before i changed the oil?

Thank you.

My scooter don't use a chain for the oil pump.
The starter clutch has a gear behind it which turn another gear which rotate the oil pump.
Here is a picture from when i did the engine rebuild about 2 years ago.



I'm still waiting for the gasket to arrive so i can open the right cover. The post really slow this time of year.