If it has been sitting for a while I strongly recommend you remove the carburetors and clean them thoroughly, you will need to make sure you remove all the jets, especially the pilot jets because that is the smallest jet in the carb that will plug and it is often the one that will prevent the engine from starting.
Try using some WD40 in the back of the carbs when you try to start it after you clean the carbs. I don't like to recommend starting fluid because it is volatile and can easily catch on fire if the engine backfires.
I'd also recommend replacing the spark plugs as well. Make sure you have good fire. (turn the motor over with the plugs out and grounded on the head to make sure you can see the spark)
I also recommend pouring a small amount of Marvel Mystry oil down each spark plug hole to help "reseal" the rings. Remember that sitting is not your friend and you may have to get the rings back to life by using the special oil.
Just remember you need three basic elements to make an engine run:
- Air
- Fuel
- Spark
If you have all three of those and compression your engine will start.
Let me know if you have any further questions.
Regards,
RSelvy