10-31-2017, 08:02 AM
E.C.'s instructions on fulcrum height seem vague to me, because I don't recall where he's measuring from: the as-cast bottom of the dished area, or the machined gasket surface? I'm pretty sure he's referring to the machined gasket surface. You can lay a stiff ruler across the surface and measure the depth with you caliper (but first zero out the caliper on the ruler's thickness.)
As far as a good pop-off number: with a single HL on a 100cc motor, IMO you will have enough air speed (and therefore venturi vacuum) that a broad range of values would work. Just put it together with the parts it came with and it should work. If you measure it, I'm thinking anywhere from 7 or 8 psi to 15 psi.
As Steve O pointed out, there are nuances to this, but this should get you running.
Too low and the fuel pump will sometimes overpower the inlet needle, and cause flooding.
Too high and the motor will "stand up" like it should when you whack the throttle open, but will promptly die 1/2 second later.
As far as a good pop-off number: with a single HL on a 100cc motor, IMO you will have enough air speed (and therefore venturi vacuum) that a broad range of values would work. Just put it together with the parts it came with and it should work. If you measure it, I'm thinking anywhere from 7 or 8 psi to 15 psi.
As Steve O pointed out, there are nuances to this, but this should get you running.
Too low and the fuel pump will sometimes overpower the inlet needle, and cause flooding.
Too high and the motor will "stand up" like it should when you whack the throttle open, but will promptly die 1/2 second later.