I bought a 2001 Yz250. Top end power seems poor. Bike pulls well down low, then runs out of steam feeling lean. It has new crank bearings and seals, barrell re-plate and piston kit, plug, air filter, new jets stock apart from a leaner 48 pilot. Ignition timing and float level ok. The power valve appears to be working ok but is it possible to check if the valve is timed correctly and opening fully? Any other ideas?