Hi all...sorry if this is a question that has come up in the past. I attempted to search through the forums but couldn't find an answer to my exact question. In the off season we picked up a ShiftUp Spartan big valve head for an xr/crf100. The plan is to put into our race bike that is currently running higher lift Megacycle camshaft. After looking at the ShiftUp head we noticed that the valve steams and springs are significantly smaller than what we are currently running the stock head. As a matter of fact when you look at the Megacycle catalog it specifically calls for using heaver springs. So the question is has anyone else had any experience running this head with anything other than the stock camshaft? If so what is the lift and duration of the camshaft you are running and have you run into any issues with valve float, or dropped valves? Thanks for the help.