Gas, spark, and compression. It sounds like you have already know that you have good compression but you might want to check it anyway. Next remove the spark plugs and check for spark. Then go after fuel, making sure that the inside of your gas tank is very-very clean.
Now the carbs. Confirm the thread size of that bowl screw which might be a 2BA and install a threaded insert of that size. The Norton Andover website could likely have that information. I don't know monobloc carbs too well but if the float bowl is made of any type of plastic or composite material replace it.
Check to make sure that the inside of the oil tank is very clean. Rust and dirt are not something you want in that tank
Before starting make sure that the correct amount and type of oil are in the engine sump and oil tank.
Overall it sounds like you are on the right path and if you continue to plug away at it you will get it running well.
Now the carbs. Confirm the thread size of that bowl screw which might be a 2BA and install a threaded insert of that size. The Norton Andover website could likely have that information. I don't know monobloc carbs too well but if the float bowl is made of any type of plastic or composite material replace it.
Check to make sure that the inside of the oil tank is very clean. Rust and dirt are not something you want in that tank
Before starting make sure that the correct amount and type of oil are in the engine sump and oil tank.
Overall it sounds like you are on the right path and if you continue to plug away at it you will get it running well.
