I have tried many technicians but none have solved my problem. I had problems in the past past, but one day my bike started to make a noise while opening the throttle when cold after about 50km/h speed. The noise sounds like the choke is on. After some months it was getting worse. When hot it, seemed ok. One day I could hardy go over 30km/h anymore.

I cleaned the air filter two years ago. I told the technician that I suspected the air filter might be the problem, but he told me no! He told me that because I had done boring he put a bigger main jet! Then it was running ok but after driving when it stopped I had a drop at idle. Next day I had to try 30 times to start it manually. Then it turned off on its own when braking or at a stop. Once it warmed up it seemed okay. The noise was still there. They told me that it was normal to hear noise when cold. I had to wait 5km in order for this noise to stop. Then next day it got worse. I tuned the carb, then it was fine at idle, and it started great. But after driving fast 80-100km/h, when I was stopped it turned off.

The day after that things got worse. I couldn't go faster than 30km/h again and I heard the noise. Fuel consumption was 2x because of the main jet. I decided to fix the problem myself again. I removed the air filter box and it had some insects inside and seemed black. I installed a cone air filter I had from previous owner. Then although cold start I had problems but that noise stopped and although cold it could go fast without problems and no noise. But throttle response was weird. I guess that air/gas mixture is screwed ? Should I go back to my old main jet and buy a new filter? And why does it turn off when I stop ?

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    What does the spark plug look like? Done any plug chops yet? I wouldn't mess about with the mixture (which you are doing) without testing the changes either using a wideband O2 sensor (probably not going to work well on a scooter) or at least some plug chops with a couple of fresh spark plugs. – Timo Geusch Dec 21 '12 at 1:43
  • at morning i'll check how it looks. As i read/know i should check after running full the color ?Does it work when running at 1/4? – GorillaApe Dec 21 '12 at 2:24
  • Do you still have this problem or have you sold the vehicle off? – DucatiKiller Dec 28 '15 at 21:25

This sounds like an air leak to me. Do a leak test, by spraying carb cleaner or starting fluid on the intake, carb and around the head, while the bike is idling. If it starts revving when you spray fluid, it's leaking air. Replace the gasket/tighten up nearest where the rev-producing spray occurs.

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    thanks for responding but its 2.5 years late :) Somehow another technician made it work almost fine but bike got stolen last year. Thief had stolen 50 bikes and sold parts. He stayed 6 months in prison – GorillaApe Apr 21 '15 at 12:20
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    the next user who comes along will be helped by the answer. Sorry to hear your bike got jacked – Chris McCall Apr 22 '15 at 15:17

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