my 2000 XR50 starts up 90% of the time. but when it doesnt, IT DOESNT. i have to clean out the plug which has carbon all over it. Also, when it idles sometimes the idle drops off by itself, and when u look at the oil, its kind of watery feeling and smells funny. what could all this mean? i have a bbr exhaust but the jetting is stock and the filter is clean. any help would be appreciated.