I've acquired a model with an old Kalt 22cc (basically a Zenoah 23cc magneto) petrol engine, initially it wouldn't run so I replaced the rubber bits in the Walbro carb (WT705), it runs now but I can't slow it down. As I reduce the throttle the engine revs drop to just under 3,000 rpm, but then reducing the throttle further sees the rpm increase. At full throttle it's turning a 16 x 8 at just under 7,000 rpm.
Any suggestions?