After replacing the generator cover, when I had repaired the gear-change mechanism, I had an oil-leak that seemed to come from the region under the solenoid. I thought I had not placed the gasket correktly but when removing the cover once again I saw that the gasket was OK. The oil-filler-plug was missing the o-ring: could this be the reason for the oil leak?? Or it's something wrong with the crancase breathing??