Jan - I've fiddled endlessly with the high speed and low speed needles trying to get it to run right! It's on 10% nitro. Yes, I think it's not getting enough fuel at high throttle, but it does that no matter how rich I make it with the needle.

Aerowoof - Grateful for your input, I'll check the valves when I can.

MinnFlyer - It's a Mk1 surpass without those nipples you described. The only nipple on it that doesn't have a tube connected to it is the one on the very bottom of the crankcase. Good suggestion about the valve housing though, thank you. I'd thoroughly cleaned the carb through in case of blockages, but not that area.

Thanks to all of you - it's so nice of you all to try and help.

Jason.