So that's what I'm going to do:Use that engine.
the SP engine is worthless. For some magic reason the exhaust valve has hit the piston (only just, but I presume the valve will be bent). I don't know why, I checked the position of the camshaft more than twice, it was fine. Tension on the cam chain was also fine. It's a mystery for me, but I'm really glad I can get this engine out.
Besides the piston hitting the valve it also turned out that the oil breather is clogged up and I already knew that the clutch isn't 100%. Heap of junk.