I am doing a Yamaha RD 250 522, which has been standing for 20 years to get back in order. I wanted to expand the carburettors, but the gas sliders are boom-proof. The bike is in a bad condition. In the carburettors a covering has formed in the float chamber of old petrol, consistency between stone and rubber, which I can only scrape out. Ultrasound can be forgotten here. I suppose the same residue holds also the gas sliders. With pull or push through the egg noss (screwdriver) is nothing to do. How glued in. Rostlöser is pointless (Alu), creep oil does not help. Does anyone have an idea with what I can solve this solid covering? Or carburettor cut off, dispose, buy used? Thanks in advance! Gruss, Rick