I had a very similar dumb moment, my Comet had never had the nice little gear position indicator fitted, and someone pointed this out to me, Marcus Bowden I think, I saw a pair being offered for sale on eBay I think, really nicely made from stainless steel, after a very small amount of fettling with a swiss file the two parts were fitted, don't really know why I bothered, does anybody actually look at them when riding or stopping. Anyway that is when my problems started, just occasionally falling out of the gear that I had selected, it wasn't that frequent, just now and then the revs would go through the stratosphere, but it drove me crazy, so I phoned my good friend Hugo Myatt, he is my first port of call for all Comet related problems, his very first comment was "have you messed around with or fitted new gear lever indicators, they can foul the gear lever and stop the gears engaging fully, Bingo! Thanks again Hugo.