Motorcycle Repair: 2000 suzuki katana, info ie, starter relay

Question
it acts like it wants to turn over but will not start.I checked the plugs they were dark and smelled like gas,but other than that the fuses look good fuel filter could be changed.
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The text above is a follow-up to ...

-----Question-----
I bought this bike and it started when I got it but after putting in another battery it won't turn over.The guy I bought it from jumped it with a car charger.
-----Answer-----
Hey Fred,It sounds like you need to place the battery on charge.After charge (12.5v @ battery)make sure the connection are on properly and tight.If still does not turn over you will have to give me a little more info (ie:does the starter relay just clicks or there is no clicking).

Answer
Hi Fred,If the plugs are dark I would replace them with new ones.Before installing them make sure they have a strong spark to them.If the bike fires up my next step would be to check the charging system,then take it on a 10-20km ride to get a better visual on the plugs to see how they are burning.