So I had an attempt (this is my first go at anything with engines!) to take head off, and was doing ok but slow progress, my friends brother came over (he has got a motorsport engineering degree) and very kindly dropped the engine out and took off the head (with help from me and my friend)
Turns out a ball bearing got in cylinder 4! Baffles me how it got there!
See pics below!



Exciting ay?

Anyway I've now got replacement head, pistons and barrel so hopefully in next few days I be able to sort it out!
