I have bought a used Benelli 491 in 1999. I have the problem that the scooter accelerates very badly and simply does not come from the spot. According to Tacho, I reach the mountain from 60 to 65kmh. On low gradients I reach a maximum of 10 to 15kmh. If I give full throttle in the stand, I can hold the scooter without problems with the two legs at the spot. On the level I need vo n 0 to 40kmh easy 60 seconds. You notice that the scooter stays stuck in the lower speed range and simply does not get any further up. As if the power is missing. Reverometer unfortunately I did not install any. What I have already done: Clutch springs replaced. Yellow were in it. I removed them. Then polini 5000rpm and 6500rpm installed – no difference detectable Front is a small ring on the shaft from the previous owner. Thus, the belt lies completely on the shaft. Variogewich 6,5 grams was installed. Then converted to 6,0 and 5,5gr – both times no difference can be detected. Counter-pressure spring nothing changed. Carburettor removed and tested: main nozzle 74er installed. Side nozzle 38er. No exchange performed. With a picture of the spark plug. New air filter purchased and installed, but still original and no sport air filter or similar. Petrol hoses replaced Did you give me tips on what I can still check? If information is missing please report. Greeting Tim