4 things to make a motor run
Fuel - check the pressure into the carb, might have to plumb in a gauge. Also verify visually that the fuel is spraying thin (not drops) out of the carb and isn't flooding the motor. The motor will actualy idle ok a little lean, but won't idle very rich.
Spark - Timing light on the tip of each wire near the plug with show all cylinders are getting spark (timing is another issue). However a timing light on 1 cyl will show if the chain jumped.
Air- Have to assume intake is ok... anything in the exhaust that could be plugged?
Compression - run a compression test and a leakdown test.
Special Thanks and Recommendations to;
PAC Racing Springs
Joint Clutch and Gear