I'm guessing you are faily new to these old machines, sometimes we get a bit over complicated on here, we mean well but we tend to confuse.
I like to keep things simple, cheap and basic so if you are going to buy
anything make it new spark plugs.
You are getting gas and you have spark, that's 2 outa 3 (Hail Meatloaf).
Its been sitting for a long time so any number of things may stop it running, fresh gas and new plugs usually gets me half way to a motor that runs, after that its the tech stuff like timing (a science all its own) air/gas mixture (carbs and they are a true #$%*) compression (how nackered your engine is internally).
You mention that gas is flowing (even filling the exhaust) so sounds like your float valves are stuck wide open, maybe the bike was left sitting with all the petrol drained from it and the tiny drop down valves in the carbs have jammed (rusted) open.
Only removing the carb float bowls will prove if this is so, I don't own a 550 so not sure if your carbs are screwed on with 4 tiny crossheads or you have one large clip thing to secure the bowls.
If you get the bowls off and its full of bright orange stuff, that's rust and you are seriously on the back foot, they will then require total strip and rebuild with a few new parts probably too.
Jammed valves in the head will also let fuel run through the motor, depends where the bike has been kept and how much weather/water has got into it.
Is your battery fully charged? these SOHC 4's eat batteries on startup so if you are down on power it will only get worse.
Cleaning the points can only help get her started, I was always taught to use a non shiny business card to run through them a few times, you'd be amazed at how much crud comes off them.
Sorry but its a huge learning curve when you take on a SOHC 4 but as rewarding as anything when you finally get her running right.......best of luck....Hush.
