Hello dear forum, I am in possession of an Aprilia RS50 Bj 2006 with D50b0 engine. She has run 6500km and I am a little confused about the engine. She only pulls really nice up when it has become really hot, means 1-2min full gas, on the country road for example. There I manage 90 kilos of knocks smooth 100kmh, if there is no wind there with the series cylinder, carburetor and exhaust. However, if it is only a bit colder, there is the power band of 5500-7500 revolutions and pulls very weak. If it is hot however, it starts at 7000 really and then it stops at 10000. Between 5-6 thousand it has a short hole, like with a sports exhaust, but only if it is really warm. Another thing: in the past an MVT 75 cylinder was on it with Gianelli exhaust, so was probably already made at the carburettor, only the previous owners were… let’s say quite layishly on the road, because we have seen how together the mopeds are I guess for the time being it’s always too lean, but I’m not a professional, and I don’t have much experience on the subject either, so I’m going to turn to you! I’m happy about every answer and apologize if the text was incomprehensible. VG