Help firing problems with cbr 900

Hi I'm new here and I've just bought a Honda CBR 900 1996 from a friend and when I first had it - it started ok. Since having it for about 1 week I have noticed it wont start properly - I can hear it turning over but not firing - so I bought new spark plugs and air filter as they had never been changed and now it starts but it back fires, splutters and generally sounds like its going to konk out - the timing sounds out (slow) and when you ride it it back fires and sounds sluggish - I dont know if I have put the spark plug leads on wrong - would anyone be able to help me know which ones go where????

Hello, I think the best answer I can give to you is to go on this site. Pdf.com, put in year and make of bike and then download a repair manual for you bike and then review the manual on your firing order and go from there. I'm no bike mechanic but if your firing order is right you might have a bad coil.