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I think whirling sound have nothing to do with the air filter.
this is probably because of worn cvt rollers. Try replacing it.
It's cheap and makes better take off.

Other cause might be valves. Try adjusting valve clearence.

Both worn rollers and valves makes some sort of rattle-noise during acelleration

How many km's you have on your scooter and have you changed rollers and adjusted valves yet?

Hi all

I would like to share my scooter experience and thank you people on a helpful, detailed posts

I bought scoot new,

- 500 km (first service) - semi-synthetic 10w-40 Motul Scoot 4T - drove it carefully and waveing? throttle to brake it in (my mechanic advised me not to brake it in 'fast', 10 x 15 seconds full throttle than pause of 1 minute up to half throttle). Top speed 40 km/h
- 1000 km (second service) - semi-synthetic 10w-40 Motul Scoot 4T - still drove it carefully but full throttle for short time. Changed transmission oil, installed smooth variator boss and 82 jet. Top speed 53 km/h. I felt speed increase gradually wich is correct by factory instructions. Fuel consumption 2.5 liters/100 km
- 1500 km (decided to do this service by myself) - regular 15w-40 Valvoline Car Oil. Cleaned and adjusted spark plug (0.7 mm) and removed, cleaned and adjusted carb. wich was very dirty. Engine took much less time to warm up and got some more start and mid-range power. Top speed still 53 km/h but mineral, factory recommended grade oil made engine run and feel much better, and there was no oil residue in air-box compartment. I think that correct oil viscosity of 15w-40 sealed piston and cylinder as it should and there was no oil burn.
- 3000 km (third service) - semi-synthetic 10w-40 Motul Scoot 4T - again oil residue in air-box filter. Changed oil again by myself with mineral 15w-40 Valvoline Car at 3500 km.
- 5000 km (fourth service) - semi-synthetic 10w-40 Motul Scoot 4T (my mechanic uses this one and I'm doing service because of warranty. He said Kymco Sigma 15w-40 is not availiable).
Changed transmission oil and new NGK sparkplug installed. Scooter felt a little bit 'sluggish' first 30 km after service but was ok after.
- 5300 km (service by myself) - fully-synthetic 15w-40 Motul 3000V (hard to find), cleaned and adjusted sparkplug at 0.7 mm gap and de-restricted CDI by cutting it.

CDI de-restriction was interesting because I needed more speed but was afraid not to destroy it. I decided to give it a try. All I could loose was 30 USD wich is the price of new OEM CDI. After reading some posts and watching a video I decided to give it a try. Cut through a copper wire, silicone sealed and taped with electrical tape.
Got 62 km/h at flat road and better and constant acceleration. Definitely was worth it. Fuel consumption 2.8 liters/100 km
I'm tinking of installing 7 grams rollers because engine has at least 20% more power.

I advise CDI cut not to be done before at least 2000 km. In my opinion this is the mileage where break-in period is 100% done on this little engine.

Other things that I could mention is that vacuum tube at the right side of the frame was replaced. Made of low quality material and clogging vacuum, causing engine to cutt-of. Engine heat was making it soft.

Speedometer needle was stopping at 20 km/h. Solved after visit to dealer. Re-routing speedo cable solved the problem.


My advice is to use 15w-40 oil that is recommended by factory. In my opinion it's the best for the engine.
Full de-restriction and full-synthetic oil after 2000 km.
Oil change: mineral at 1000 km, full-syn. at 2000 km and regular services with original and correct parts and it
will last very long.