Ahh it's a sad tail. They were banned for two reasons - to reduce speeds so the tracks would effectively be safer. Second which is the one you usually see is cross winds, they said it made the bikes too unsafe in cross winds.I've been reading quite a few m/c "history" journals lately, and something has come up that I wonder if anyone around here knows more about it (he looks pointedly at MSCUDDY).
Sometime in the 40s or 50s, it appears that "Dustbin" fairings were banned from motorcycle racing. If you're not familiar with them, "dustbin" fairings were very large, very rounded fairings that usually included a long, torpedo shaped nose section and then a quite full faring back around the rider's legs. It seems like it was a very big deal at the time, and had a major impact on racing.
Why did they ban those big, and IMHO, beautiful fairings? Was it a safety issue? Were they trying to make the race bikes more like the bikes they sold? Enquiring minds want to know!
While I'm sure it made the bikes somewhat less safe in cross winds I think it would only be a big deal at a track with a lot of wind. I race out at Willow Springs and there have been a few times it's been 40 mph winds in those conditions I am glad I haven't had one. But in less extreme conditions I think they'd be fine.
Sadly ever since they banned them in premier racing they're now banned in all the racing I know of. Because of that they're no long put on production bikes and aren't even offered as optional parts.
It's really a shame considering it can really boost high speed performance, it could really be a great help on a low hpr bike like a Ninja 250, or gs 500. It also GREATLY improves mpg. My father helped make one for a friend, mpg doubled on freeway. You can further increase it by changing your gearing to fit your new top speed and putting some good tail bodywork on it. You can look around online there are bikes with modern dustbins that will get 200, 300 mpg.
Maybe someday I'll make one for my 125, thought it's illegal for racing it could be fun for track days Yes I think they've very pretty too, and I'd love to see what a modern production sprotbike OEM one could look like.