OS 120S III. Pump Bypass Conversion. Test Runs After Service.

The OS FS 120 engines are absolutely beautiful and powerful machines. I did another pump bypass on this one for the pump and regulator was leaking. They just don't last and they don't make them anymore. This engine needed a service and bearing change after not been in use for some time. The plastic and the diaphragm rubber gets old and just won't seal anymore. If you have this problem just do this easy bypass and it will run absolutely perfect. There is normally just a screw in the muffler that can be replaced with a nipple for pressure to the tank.