These work. Punch out your screen and install one for better engine breathing, less gasket seepage and more power. 1. Punch out the steel screen 2. Grind and smooth out the remaining spot welds which are left behind. 3. I use a little "Right Stuff" or your favorite sealer down in the bottom of the breather. 4. Install with the supplied set screw through the bottom breather hole (add a little locktite) even though the screw can't go anywhere once the breather is in the case. I have a few for sale if you really want one. $35 Fits: '83 and earlier shovels, pans, knucks . . .
PS. I also like to 'square up' the breather hole in the case itself (I have S&S directions if you want specifics - I can fax to you if needed.