No I dont think that the scraper would contribute to this problem. The piston is lubed by waste oil from the rod bearing, wich also lubes the wrist pin. The change to a scraper actually caused the engine to run cooler and with more power.
By all means ck the oil pump. Is there good return flow to the tank? Let it run a few minutes with the bike straight up then kill it and remove the oil level plug in the crankcase. The oil should be just dribeling out this plug hole( bottom of crankcase just above the drain plug )But I doubt its a oiling problem.
What pistons are you runing? Stock pistons were set to .004" at the factory but most rebuilders went with .006".
Are you fanitical about intake leaks. Your bike should have the castiron intake manifold witch is better, If you have the alluminum manifold inspect it for dammage and cracks replacements are aviable. For either manifold replace the sealing cones. Some machine a grove for a O-ring in the cones.
One last thought Have you checked the rods for straightness? If you are just doing a top job put the wrist pins in the rods and with the crank at bottom center measure the distance from the pin to the machined surface that the cylinder mates to. Should be the same on both sides.