Martyn was spot on. Its a bagster cover and they make tank bags to fit.
This is my everyday ride so i don't have any very flash photos, but here's a couple I took this afternoon. I put one in of the build to show the frame changes and a bit of the underbody. It has been about a four year project but I can only do stuff that takes more than two days when i have holidays. When i started I didn't know squat about wrenching or engineering but I have learned A LOT on the way. Folks on this board gave directions provided info and pointed the way, and blokes like Patrick from Germany tweaked my conscience to do better. He reckoned my welding looked "country style" so I looked, realised he was right and did it again. Some of the bits have been done four times over. My wife reckons I'm a bit of a pernickety bastard.
Still a bit to go. I have to remake a new stainless mount for the shorty muffler and I am considering a different mechanism for attaching the shock absorber reservoir (it normally goes on the passenger peg bracket.)
I heard some fellers the other day talking in the office about the new model that BMW had released. They were opining that it was a foray into the street machine/monster market and was clearly aimed at the likes of Ducati. I was pissing myself laughing. When i told them that it was my bike and it was 12 years old they thought I was having a go. I still think that at its basic level it is the loveliest roadster that BMW has made in a very long times. The newer designs look "wimpy" to me but that is of course a very subjective opinion.
(everything is painted to match now and the subframe was powder coated, the underbody parts were fabricated in 3mm kydex,)
It has been a blast, although sometimes I have wanted to tear my hair out.