After much Googleing, I found this: Fuel Pump Diaphragms: The tan Teflon coated pump diaphragm has been superseded by the clear mylar diaphragm. If your carburetor does not have a machined fuel pump surface you cannot use either the tan or the clear diaphragm. You must use the black buna diaphragm also found in the kits. All three diaphragms found in the Zama carburetor kits offer resistance to alcohol fuels. My question now is...can I use the black buna diaphragm instaed of the clear mylar is I suspect problems with the mylar?. I assume that is the thin black one in the kit. Thanks