[FlipFlop]

Why did the person sell it, is another consideration.
Has the carbs been messed with?
Was it a parts bike that might have parts missing?
Either way sounds like the carbs and I would add the spark plugs (and mayhaps wires) as a good starting place. Also would not hurt to do a compression test to see where you are at.

 

[FlipFlop]

Yeah def, if it was running before and suddenly done this acting up look for disconnected vacuum lines. The bike needs to be running if you spray things to test.