Oh dear
,
Lets look at this current situation in two sections;
firstly the flywheel;
make sure that the new woodruff key is a good fit into the crankshaft and the flywheel
next that the taper of the shaft and inside of the flywheel are not burred, clean them up as best as you can
carefully align and refit the flywheel plus replace and torque set the securing nut
secondly the compression;
recheck valve clearances and then need to check out the compression which you can partially do using a standard compression gauge, this method will measure the compression as the engine is spun over with the throttle held wide open and the ignition coil plug lead earthed to the the frame (fully charge the battery before conducting this test as rotational speed is important)
the best method to test is with a workshop air compression tester which is; an adaptor that screws into the spark plug hole, the engine is locked into the TDC position on the compression stroke with both valves closed; compressed air is then fed from an air compressor through the adaptor into the cylinder and you check the gauges (most have two gauges - one is the line pressure and the other is a percentage leakage) but at the same time using all of your senses check for air escaping from the cylinder;
air leaking through the carburettor with petrol smell indicates that the inlet valve is not seating; air leaking down the exhaust pipe will be heard at the outlet of the silencer; air leaking past the piston and rings will be smelt by oil and air through the oil filler in the crankcase or breather pipe outlet; (on liquid cooled engines check for possible fumes and bubbles in the coolant and on multi cylinder engines listen at the other spark plug hole/s which would indicate probable head gasket failure)
Unfortunately this test is normally only carried out by a professional garage that has full workshop tools.
If you have access to an air compressor but not the gauges have somebody push an air gun or tyre connector up against the spark plug hole whilst you listen/look/sniff as previously described, might give you an idea of possible problem/s
Other than that now I can only suggest that you seek help locally from the local Group or take the bike to a repairer of trusted capability in your locality. Let us know how you get on, fingers crossed
TTFN
Hugh.