1973 harley aermacchi x90 starting issues
Does the plug come out looking wet or dry? Maybe the ignition timing's way off. Dou you get a big, fat spark? A plug can be too fouled to run, but still show a litle spark. Are the spark plug threads clean? They form the necessary connection to ground that allows a spark. I thought I was being real smart when I put never-seize on my bike's spark plug threads. That was enough of an insulator to keep it from sparking. Two strokes, especially old ones, can really be affected by worn crank seals. Two strokes need compression on both sides of the piston to run right. Does this engine have a reed valve in the intake? If it's worn, that's another place to lose bottom end compression. Exhaust port or muffler clogged w/carbon might also keep it from running, but it would a least try to fire.
Try starting fluid.Mine was sitting for 20 years before I tried to start it and I was getting spark and fuel and all but would not start.One squirt of starting fluid and it started right up and has been running fine since.I think if they have been sitting a while they get too wet in the cylinder to start with just the spark plug.