New here and new to Yamaha. recently purchased a 96 royal star tour deluxe. I have replaced the plug,s ,oil,filter and cleaned out the carb,s with seafoam. My problem is a mid range shake . When I roll on it seems to run on 3 maybe 2 cylinders. If I run it hard from take-off, it move,s out well Any idea,s as to were to look thanx Doug