Hello guys! I'm Sandor from Hungary! I have a bit similar,but not the same problem with my 532. It is a two carb version. When I bought it it was on shelf for 5 years. It was not working as it should. It dropped the rpm after 10 sec 90-100% gas and stabilised at approx 60% rpm . At that time the water temp getting to be higher and higher up to 100 C°. So the mixture was lean. I checked the carbs and recognised that ther are nothing good in them. I put new float arms,needle jets 2.72,jet needles 11G2,two new airfilters. I adjusted the carbs as it written in the manual. The engine did the same shit. From that point I tried everything. I wanted to bypass the vacuum pump so I made a gravity tank, but the engine was a bigger shit without the Mikuni. Should it work with just a gravity tank,without fuel pump? So I found the hole at the float needle too small. It was ca. 1 mm,while the main jet and idler jet together is 2.2 mm. Did all the Bing54s have the same size (1 mm) or exist a bigger size type? So I drilled the hole to 2 mm and adjusted the float level to the required level. The engine started to work almost as it should. Now it can keep the maximum rpm,but above 50-60% rpm it overheats to 90-110 C°. And if I set the gas to a position the rpm slowly changes. It seems sometimes lean sometimes normal the mixture. Now I have really no idea what I should do. Please help me.