ruffdog
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- Dec 31, 2011
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- Bobcat Toolcat 5610G, Deere X744, Cub Cadet IH 982
Yamaha had the YPVS power valve and other makers had theirs too:That was then. Look up "power valve". The exhaust port timing is controlled in every modern 2-stroke dirtbike the past 25 years. Lots of discussion on KTM forums as to the most desirable spring to control the opening for different conditions. Beta adjusts theirs with a threaded shaft making changes in the woods very easy.
The last RD400 was the first I remember having a power valve in the exhaust.
Two-stroke power valve system - Wikipedia