Hello everyone!

so another newbie and not surprisingly I need advice. My 09 xt660r is suffering from surging. It hasn't always been like this and has only suffered since I had the coil replaced at around 1500 miles. I've tried increasing the co as instructed somewhere on this site which hasn't worked. Ive looked at the idle speed but it doesn't sit at one figure in fact its up and down like a yo yo. Is this normal? Should the idle speed sit at a constant figure? Any suggestions will be welcomed. This is my 2nd xt and I don't understand why when I bought it it was fine and now it surges more than my old 05 model.

Dave B