Thanks Dave, I re-read my previous post and it didn't read very clear. I replaced the 2nd pump with a new pump not long after the problem started so it's on it's 3rd pump now, and it hasn't seen much work yet. I did disassemble it and flush it between flights while the plane was charging but it made little difference.
There was fuel in both valve lifters and fuel pooling in the crankcase when I pulled it apart the other night. In a perfect world, fuel goes in at the intake valve (I've got the sub needle closed at the moment), is burned, then shot out the exhaust. There shouldn't be raw fuel in the crankcase or cam area unless it's leaking from the throttle assembly, pump or the intake valve isn't sealing. Surely the old (2nd) pump wasn't leaking into the cam area and the new (3rd) pump is doing exactly the same?
It wouldn't surprise me, I had to send back a brand new back plate assembly because it was faulty out of the packet. Imagine my frustration to fit a new back plate assembly, turn it over by hand to check the spark, head out to the field and then not a single pop when I tried to start it. It'd spark when turned by hand, but no spark when turned by the starter. How does that happen???
If the weather holds I'm heading out this afternoon with the valve clearance set to the full 0.1mm, and a new spark plug set to 0.35mm. Fingers crossed...