elanner wrote:What the heck is "29mm + 4.5mm" trying to say (aside from the obvious 33.5)? This is totally different from the 25mm generally suggested. The note neglects to mention that you need to remove a jet in order to do any measurement, and "Remove some fuel from the carbs" seems bogus too.
Nick,
The correct fuel level for a DCOE is either
29mm +/- 0.5 mm (1.142 +/- .02 in.) with the top cover OFF, or...
27mm +/- 0.5 mm (1.063 +/- .02 in.) with the top cover ON
...... (+ or -)
Remove the top cover, then notice that the top of the carb body, and the top of the jet pedestal in the middle of the float bowl were both machined in one pass to one flat plane. The fuel level is measured from that plane down to the surface of the liquid pool.
If the carb is mounted at anything other than dead level (most are at some angle), then the fuel level measurement will vary with where around the bowl you take the measurement. Therefore, the measuring point is standardized as close to the center as possible. The Jet pedestal is in the center, mostly blocking that measuring point. But in top-view, the pedestal is not straight-sided, and one side dips inward between the jets. So either measure in the center of that dip, or remove one main jet assembly and measure down in the empty bore.
The engine will start and run on the idle jets, so having one main jet assembly removed will not prevent the engine from running.
Scooping out some fuel first lowers the fuel level, ensuring that it wasn't artificially too high for any reason. Then, with the top cover in place, running the electric fuel pump, or running the engine to operate the mechanical fuel pump, let the fuel level rise until the float turns off the fuel inlet valve. That procedure ensures the fuel level is now correct for measuring.
Remove the small round jet cover from the top of the large top cover, and use the depth gage feature of a caliper to measure down from the top of the jet pedestal, through the empty jet bore, do the surface of the fluid pool. With the top cover in place, and the floats in the fuel pool, the correct level will be 27mm +/- 0.5 mm (1.063 +/- .02 in.) down with the top cover ON.
If for any reason you cannot make a measurement through the small round jet cover opening, then remove the carb's top cover for better access. However, note that as the cover is lifted off, the floats will droop, the inlet valve will open, and any residual pressure in the fuel line will squirt some additional fuel into the bowl, giving a bogus measurement. So before removing the top cover, first disconnect the fuel line, venting any residual pressure and draining the inlet port.
When the top cover is removed, the floats will be withdrawn from the fuel pool, and the level will drop accordingly. So fuel level is now further down with the top cover (and floats) off, and the measurement is 29mm +/- 0.5 mm (1.142 +/- .02 in.).
Bend the tabs on the float assembly as required to raise or lower the fuel to the correct 27mm with cover ON, or 29mm with cover off.
The cover-OFF dimension is correct for the old style round, brass floats that were used in Lotus TC applications. The later plastic floats will require a different dimension for when the top cover (and floats) is removed. The 27mm cover-ON dimension is the same for both types of floats.
*~*~*
The stock Weber Inlet valve pin is all brass with a solid metal point. Some aftermarket valve pins have a rubber tip The rubber will take a compression-set after a few days, allowing the pin to seat a little deeper, the float to rise, and the fuel level to become too high.
If you use an all metal inlet valve pin, you can set the fuel level and forget it.
If you use a rubber-tipped pin, then go back in and re-set the fuel level after a few days.
Regards,
Tim Engel