Mid 70's 650 Bonneville I think it is the oil in the frame model, they can be prone to cracking the frame and losing the oil. John.
A real nice machine...if you're good at it. A little seam weld on the frame MIGHT break if you abuse the poor thing by startin it on the center stand. Well engineered light weight frame, steers and handles well. 50 HP, real flat torque curve, easy to keep in tune. I got mine down to 363 pounds with full street equipment. Helps if you're tall, it's a pretty tall bike. The frame was lowered next year. What are you gonna do with it?