So I dragged this wee beastie back to my place last weekend:
The body's fairly well rooted, the tray's solid but missing bits, starts, stops, shifts and steers quite well, but the poor old thing wasn't running right.
Cylinder four wasn't pulling its weight.
At all.
Plenty of fuel, air and spark, but the compression was down severely.
I immediately thought 'rings', but usually rings (especially in these tough li'l f*ckers) all wear down evenly, so I was thinking it was either a burnt-out valve or a hole in the piston.
I crossed my fingers, hoped that it wasn't a lightweight piston, and pulled the head off.
So the bores are squeaky clean (no scoring or glazing and a tiny lip at the top) and the tops of the pistons, bowls and valves are covered in carbon, but I did find this:
Ah-huh! The culprit!
The plan is to clean the bowls, valves and pistons (as best as I can without tearing the engine down) and throw it back together, although I am very, very tempted to tear the entire engine down to its undies, clean everything (the oil's black as black and smells burnt), and throw it back together nice and clean and fresh-ish (I think they're called a re-run engine).
Anyone know where to get valves for these things?