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Hello Jim.This corresponds quite well with one of the brains behind the last 125 ccm engine (Frits is his firtst name)http://www.pit-lane.biz/t5121p680-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-4Somewhere in the very long thread he says that the ideal engine has a funny arrangement for inlet control like bell,disc,piston port etc for starting and low load ,but when the going gets rough, a permanent open hole is best.You will have to register to see the pictures but the very friendly administrator speaks english and the two Aprilia gentlemen only write in english.