I have rejetted my carb since putting on a home made pod kit and slip on exhaust. Sometimes worked great and others would start getting bitchy around 80-90kph. I have had a tried bigger jets leaner and richer mixture with pms screws. Today my father suggested that it might be a problem with the vent hose off the carb that maybe it was partially blocked I removed the little black filter off the hose and viola bike runs like a monster now. Can anyone tell is that a filter or a check valve and does it need to be there?