Fuel and Carburettors

Hardi Electric Fuel Pump

Grob 109 uses Hardi model H cat 2212. As of Sept 04 there is no info on this model on the Hardi website. HARDI.de electric fuel pumps

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Zenith Carburettor
The zenith carburettor can only work properly if the float level is correct. The setting is 16.5mm and I have made a very simple tool for getting this right. Anybody who wants a drawing of this just email me. If you decide to buy a tool for adjusting the main jet be aware that there are two types, slot or hex. plus some early types that have the adjustment on the bottom of the fuel bowl. The main jet tool helps prevent damage to the diaphram.

The correct needle for L2000 EB and L2400 EB is B5CK and the float chamber needle and seat is 1.75. Make sure the needle and seat is brass not nylon as is usually supplied by automotive stores.

The mixture adjustment is to compensate for slight variations in floats and the way the needle mounts in the piston. This adjustment basically only affects the idle mixture. If the carburettor is set up correctly a lean mixture can be caused by leaks around a worn throttle spindle or other air leaks. Rich mixture indicates a damaged diaphram. The oil in the dashpot is to help richen the mixture on acceleration and should be weight 68 not engine oil which is viscosity modified. I suppose engine oil is better than no oil. You can test the mixture by raising and lowering the dashpot piston while on idle - with care.

If you want to help your limbach reach TBO make sure the twin carbies are perfectly balanced with each other.

See Limbach MI 10.3 for further information.

Information courtesy John Callahan

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Grob 109 balance tube between carbs
630mm long, id approx 14mm to 14.5mm

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Tuning and Setting SU Carbs

Zenith carburetors and Zenith Carburetor parts