I think the smallest "ram-air" Suzy was the GT125. I had both a 250 and a 380, neither of which seemed to suffer in any way if the ram-air was removed. The 380 usually ran better without it as wet weather caused the plug caps or HT leads to short out. I can't remember why it was easier to remove the alloy cover than to replace the plug caps but it seemed sensible back then. There is still a ram-air system in use though it serves a different purpose and is effective. It is the air intakes in the fairings of bikes like the ZZR1100 etc. which channels the air into the carbs. The faster you go the faster the air is forced down the bikes throat. Almost turbo-like (or ram-air).
I remember seeing drag bikes, with Brit twin engines, with the cylinder heads turned round. The bellmouth of the carb/s facing forward (for the ram-air effect) and the exhaust straight out the back. I assume it was beneficial to their times but wouldn't have helped the life of the engine with all that unfiltered crap forced down the inlet.
