Be sure the bottom of the HS spring is not between the 2 parts, but against it's appropriate notch. even then, there is no 1/400. Probably never was. Top speed will never be more than 1/250 unless you put a turbo supercharger and a rocket engine on it. Be glad to get 1/200 and below The bitter truth. Congratulations. 1/400 is now your 1/200th or 250th if you're lucky. And 1/200th is your official 1/150th. When you've had the shutter apart for umpteen dozen times you will realize this.