I have a 2007 Ultra 250 and it won't go above 40 with the SFO key. It seems to be running just fine it just won't go above 40. I bought it used with about 50 hours on it. It was running at full speed but now will not go above 40. I have replaced the spark plugs and no change. Is there something I am doing wrong?
I would recommend checking inside the supercharger. I purchased a 2007 and after a couple of years, the coating on the internal blades of the supercharger broke down impacting thrust and top end speed. You can also get some indication based on the PSI gauge for the supercharger - if it doesn't go to the top end of the gauge, you definitely have an issue with the supercharger.