1978 RS knocking noise.

I'm getting this noise as I wheels the bike in and out of the garage.I'll describe it as a knock as the rear wheels turns. I put the bike on the center stand,turned the rear wheel,it seems the knock is coming from the driveshaft area. I checked the U-joint,nothing is loose.After reading other posts on this same problem I'm going to let an expert check it out.Until then should I not ride the bike?I'm not planning on a long trip but I do like to take 50-100 miles rides out on the back roads in the cool fall air.
Thanks,George

It could be anything from a slightly out of adjustment swing arm, loose drive shaft coupling, worn u-joint even the transmission tail shaft bearings gone south.

How many miles on the bike?
What kind of service history, particularly spine clutch drive shaft service have you done?

Does the bike get loaded up for touring a lot or has it in the past/

You could try loosening the rubber boot from the back of the transmission and pull it back to see if the bolts are loose or there's a sign of what's making the noise.

None the less I wouldn't ride it until you at least know your not making a problem worse.

I had the same issue on my /6. Culprit: Worn u-joint.
For 60 bucks I got a good used swing arm and drive shaft. Simple swap, no more noise.

I did pull the drive shaft boot back and checked the u-joint,everything is tight.

Get a mechanics stethoscope and use it to pinpoint the area that the noise is coming from. That will help with the diagnosis and deciding if you can ride any or not.