I recently encountered a problem with 5th gear on my '79' R100RT. The gearbox had an overhaul 1 1/2 years ago when I had major repairs done to the engine top-end, gearbox and FDU. This last weekend I had gone 2 hours in 5th gear at 120 km/hr when the rear wheel gave a small chirp accompanied by a momentary rpm bounce down to 3000 rpm. Nothing else happened for 15 minutes when the m/c started surging with successive rpm rapid drops. It felt like water in the fuel or carb icing, but when I pulled in the clutch the engine reved just fine. I freewheeled to a stop to do an inspection. After starting up I went through all of the gears to 5th when the problem started again. I dropped down to 4th and put another 400 km on the bike until I got home with no problems. I was a bit afraid to test it in 5th again in case 5th gear would stop the rear wheel. It seems to me as if something has come loose involving 5th gear and tries to grab something when 5th is engaged. Has anybody out there seen this before? Thanks to everyone for their suggestions about my brake bleeding problems. They didn't work originally but I just recently retried them with successfull results.