2005 zx50. It was running fine until recently when it began to bog down with full or nearly full throttle. No noticeable breaks in gas or vacuum lines. Replaced fuel filter with no improvement. Noticed that air filter cover not fully closed as there was a screw missing in upper left corner. Could this cause it? Also gas in air filer element, which I had noticed earlier this summer. I ignored it as it continued to run fine. What is with the rubber cover over carb? Also, it has an carb overflow line? What is rubber hose coming from engine cover to rubber carb cover? Engine heat keep carb warmed up? Most likely cause of problem? Can I just strip off rubber carb cover to get at carb? Thanks.