Thanks for all the replies. I think I am going to tinker some more on it and the comment about the nitro is interesting. I have done the majority of flying/tinkerring using PowerMaster Saito 20/20 fuel (my first 4-stroke), one trip to the field I took along some 15% nitro fuel by mistake but flew with it anyway and I had the impression the engine was running better with it.

I was also wandering about replacing the carb and how much they are and I think that would maybe the next step since the engine really seems to be very serviceable even though it appears to be old and dirty (it does leak quite a bit of oil but I have been told this is pretty normal - is it?).

Cheers,

Adam