Limit Caps:

As you are aware, California Air Resources Board (C.A.R.B.) and the EPA are regulating emissions on utility and lawn & garden engines. As part of this plan, manufactures have made many internal engine modifications and now install limit caps on carburetor adjustment screws to prevent carburetor mis-adjustment that would cause the engine to exceed emissions limits.

Because of the "Tamper Resistant" specifications defined by C.A.R.B. and EPA, carburetor limit caps cannot be easily removed by a "special" tool. The caps must be destroyed by cutting the plastic in order to remove.

Carburetor adjustment needles do not always need to be removed as a matter of "practice" in order to clean the carburetor. Solvents sprayed through the feed orifices will usually rinse any residue accumulated by improper fuel storage - without needle removal.

If caps are removed, they can be purchased through your service parts system. Carburetor setting and new limit cap installation may vary from manufacture to manufacture and from equipment type to equipment type. PLEASE CONTACT THE MANUFACTURE FOR THEIR SPECIFIC PROCEDURE.

Click here for information on Limit Cap Kit.

Pop-off pressure:

A lot of emphasis has been placed on carburetor pop-off pressures when in reality they are not an important issue to the service professional. In fact checking pop-off pressure can often damage the carburetor by stretching the fuel pump diaphragm and breaking the seal of the fuel pump gasket. Rather than pressurizing the carburetor to pop-off, Zama recommends that the carburetor should be pressurized at the fuel fitting to 10 p.s.i. It should hold this pressure for a minimum of 15 seconds.

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The tan Teflon coated pump diaphragm has been superseded by the clear mylar diaphragm.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.

Presetting the mixture screws:

Before carburetor L and H needles had limit caps the standard pre-set on the L and H needles was one turn open. When we had to begin using limiter caps we also decreased the needle sensitivity in many cases. So while we still try to have a preset of 1 turn, many needles fall between one and two turns open. Another thing we have tried to do is increase the clearance between the needle and the seat to make sure less debris collects there. This is because with the limit caps on it becomes much more difficult to remove the needles for cleaning. So while the limit caps have made it more difficult to preset the carburetor and to remove the needles, they have also made it less likely that the needles will get far out of adjustment, or that they will even need to be removed for cleaning.

L and H needles:

On many of the new emissions carburetors we reduced the sensitivity of the H needle to make it easier to precisely set the carburetor mixture. The H needle on some carburetors is now the same thread size as the L needle. This can lead to confusion if you take both needles out and do not identify them. Just remember, THE L NEEDLE IS ALWAYS LONGER!

Service Parts

Zama manufactures all our own gaskets and diaphragms. We do not purchase them from an out side supplier. We have increased the number of master distributors to make sure you get the parts and service carburetors you need. Always insist on genuine Zama Service Parts to ensure the quality of the work you do.