Engine Rumble

Good morning all. After rebuilding the top end on my bike and after about 50 miles of riding i have noticed a rumble in the motor that seems to be coming from the bottom end around the bevel gear cover. Any ideas?

it's been a long time since i've even worked on aa shaftie but check to see if there is oil in the middle drive housing hopefully sometimes if the rear seal dosen't get put in correctly,the gear oil in that housing can leak down the drive shaft tunnel down to the differential, if it empties out or you don't the proper amount like if it was overfilled when it was put back on it can pressure up and force that seal out so it may be dry as well, so check the levels. are you sure that the drive gear is tourqued properly as well. that could cause noises as well.