Not so keen on castor oil now. I used to put some in my premix, but have had the scooter back on the oil pump for a couple of years....and put a dash in the tank at some stage. A few weeks ago it wasn't running too well, not taking full throttle, and you need that on a 50. So strip and clean the carb....and what was blocked ? The oil feed in the carb, and I found gelled castor oil in the tank. Cut the oil pump belt and now on premix again, the piston looked good, so took it out and cleaned it up. But it's still not taking WOT, today I took the reed valves out, all good, checked the manifold rubber for cracks and leaks. So, rich, lean, air leak, air restriction ? Restricted 2 strokes are a real mine field to play with, you can't just clear one restriction because that won't work with another still in place. I really want to cut out the cat....but would that cause more problems ? I still does 70kph on half throttle, what am I moaning about ? Sunday afternoon playing with a scooter.