YS engines use a positive displacement pump, the bottom of the piston compresses the intake charge. Look up Bourke Engine on Wikipedia:
[link]http://en.wikipedia.org/wiki/Bourke_engine[/link]
ORIGINAL: David Bathe
From what I remember from mine, the old OS 1.20 had a
genuine Roots type super charger. Albeit, simplified.<div>YS engines (certainly all of mine) don't and have never had, a super charger. </div><div>Instead, their design gives a
type of super charging
effect.</div><div> </div>