Just got my 1982 Suzuki FA50 running last night. Driving it around the block a few times I noticed a constant, loud sound coming from right beneath me. It had a sound similar to that of worn brakes being applied - not quite a grinding but definitely metal on metal. At first I thought it might be the old brakes or something inside the wheel housing.
So I removed the front tire this morning, cleaned things up, and added some grease for lubrication. The brakes looked fine and do work fine.
I took it out again after this and the sound was still there. Also I noticed that the engine could not keep its idle like it did last night. It would peter out after 20-25 seconds even after going 1/2 throttle.
Then when I got to about 20mph, I promptly shut the engine off, let the thing coast, and listened. The 'grinding' sound instantly went away and the sound of the tires moving was all that was left. This wasn't the sound I had been hearing, so I am inclined to think it's coming from somewhere in the engine.
A bearing in the transmission? Piston or cylinder? Maybe it's just the back tire (I will clean that one up tomorrow). It just kinda sounds like some lubrication needs to be somewhere... things sound dry, and the scooters movement seems under tension and friction.