thanks for all the reply's! unfortunately, we had a look at it last night with one of my friends (bit of a home mechanic).. the spark plug housing was flooded, so we thought ignition/timing was the issue, and one cylinder probably was dropping out... cleaned all this, an started it up. ran perfectly until at temp (felt warm, thermo said 1/4), then got rougher and rougher...
ther did appear to be some knocking noise as well, but this was difficult to pinpoint, as it was running so bad the exaust was also rattling. On applying gas ther was also a little almost screechy noise like a slipping belt....
on opening the oil cap and giving gas (which makes it stutter)..... exhaust fumes
Piston ring?
ran fine cold however...?