Does anyone know what can cause a primary chain case to fill with engine oil, could it be a faulty crankcase seal ?.
Thanks in advance.
Has the machine been standing for a while ?
Has the oil tank level dropped ?
If the answer to these is yes , then it's just wet jumped, ie the oil tank oil has dribbled its way through the pump into the crancase , come up to the level of the main bearing and dribbled into the primary case.
Cure , use the bike more , or leave the sump plate loose and recycle the oil dribbling down.
Ok thanks it has always wet sumped but never got into the primary chaincase, but I suppose there is always a first time.