I have spent a lot of time on the info pages for my F650GS. I had read that a projected tip Iridium spark plug would improve the slight surging that it had. Well... I installed an NGK DPR8EIX-9 Iridium IX Spark Plug during the annual service and it's like a different bike!! That $8 plug lets it run smooootthly up through the 2500-3500 rpm range. It does 50mph in high without a stumble and will pull from there like I hoped it might if I installed a $250 gismo to fatten up the fuel or something. I ran it up to 85 once and no problem there either. If you have any issues with this common complaint try one (found on Amazon). I now hear the Denso (5372) IX24 Iridium Spark Plug is supposed to be even better! I have one in my cart for the next order! I haven't had time to fully appreciate this change as I have only taken one ride so far but what a change.