Right people... bad news I think,

Iv just done a oil flush and change. I used 5/30 semi synthetic and its no better

So, it looks like its valves.

What will be my best bet? Its a shame because it sounds nice and quiet and dont leak any oil... and even though its only firing on 3, suprisingly it drives nice.

What sort of price am I looking at to get the valves replaced? If I was to get a good 2nd hand head and replaced it, is there anything I should be aware off/look for?

Cheers