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The Weber Compared to the standard Nikki, the Weber has a better functioning fuel control circuit, consisting of removable and therefore tunable main jets, air corrector jets, idle/progression jets, emulsion tubes, auxiliary venturis and accelerator pump discharge nozzles. The fuel level is controlled by bending the float arm in combination with the size of the fuel inlet needle and seat. Assuming you have already purchased a DGV, you must now make sure it is in a serviceable condition. If you do not know if the carburetor has been recently running, or if you think that it is generally in a worn out/poor condition, then it is advisable to purchase a carburetor recondition kit, as that sold by Fuel Miser. These kits are only around the $35 mark, and include all the gaskets necessary, a new accelerator pump diaphragm, a new needle and seat, and several miscellaneous copper washers and componentry. If the throttle shaft bushes are worn considerably, then it is advisable to take the carburetor to a repair shop, and have the bushes replaced. A worn throttle shaft bush will result in air being drawn through the throttle shaft, giving a leaner mixture. In a turbo application where the carby is used in a blow through configuration, then the air/fuel mix will be blown out of the throttle shaft area, not really causing any damage, more of an inconvenience, making the engine and inlet manifold dirty. The stripping of this carburetor and replacing the componentry with the new items is simplicity in itself. The top section of the carburetor is removed by removing the six securing screws, and then lifting the top off. This exposes the fuel bowl, the main and air corrector jets will be visible, as will the power valve. See picture below for detail.
It should be noted what size jets are in what location as they are removed, as the primary and secondary circuits have different jet sizes. The air corrector jets can be removed exposing the emulsion tubes. The emulsion tubes can be removed with a length of wire with a very small hook on the end. The main jets and power valve can be removed. The idle/progression jets are secured within brass jet holders and are screwed into the sides of the carburetor. These can be removed. The booster venturis can also be removed along with the accelerator pump and discharge nozzle. A can of carby cleaner should be used to blow through every single air or fuel passage that can be found. A air compressor should then be used to blow through the passages. This should remove any blockages or sediment buildups. The carburetor can now be reassembled paying particular attention to the location of the jets. The top section removed from the carburetor holds the float and the needle and seat. It should be noted that the replacement fuel inlet seat is not cross drilled like the original Weber item. If installing this carburetor on an engine with a power rating of around 95 flywheel horsepower or greater, then it is recommended that the new needle is used in conjunction with the original Weber (cross drilled) seat, as the Weber seat will allow much greater fuel flow into the fuel bowl. I have experienced occasions where a 9.3:1 compression 1600 with mild cam, port work and extractors has emptied the fuel bowl by 5000rpm in third gear from a standing start with the Fuel Miser fuel inlet seat. Installation of the original Weber item cured the problem. This was even after upgrading fuel pump voltage from 8 volts (standard) to full 12 volts. The choke system on a properly tuned Weber is rarely needed, and the removal of the choke blades will also increase the airflow capability of the carburetor. At worst, in a cold start situation, the accelerator pedal may need one pump to get enough fuel into the manifold to allow initial combustion. As the engine is cold, it will idle at a lower engine speed until normal operating temperatures are achieved. It may be necessary to hold the engine at a fast idle speed (1800 rpm) for 10-20 seconds until the carburetor idle circuit will sustain combustion. The picture below shows a Weber with the choke blades and shaft removed and the linkage access hole sealed. This can be done with silicone (as in this case) or another material such as body filler.
After you have removed the standard carby, and hopefully ported the inlet manifold as described on the Modified Manifold page, the adaptor plate can be ported to match the butterfly location of the carby. The gasket that seals between the carby and adaptor plate should also be trimmed to match the ported adaptor plate. The plate can now be bolted into place as specified in the instructions that are supplied with the adaptor plate. Attention should be paid to the gasket between the adaptor plate and manifold so that there are no restrictions to the airflow. Also note how the inlet manifold has been ported to try and coax the flow to enter the inlet runner for cylinder 4. The same has been done to the runner for cylinder 1, as these two cylinders tend to run leaner during operation due to their extra length and integrated bend.
Sometimes you may want to put the adaptor plate on the other way around. This might depend on the brand of adaptor plate you purchase. Always keep in mind, the idea is to have a smooth transition from the carby butterflies to the inlet manifold.
For ease of installation, the standard accelerator cable can be retained through the use of the standard linkage system. The disk shaped linkage as seen in the following picture should be removed from the Nikki by undoing the specified nut, and bolted to the Weber carby.
The throttle bracket that originally secured the accelerator cable adjusting section from the Nikki should also be removed. This bracket can be cut, drilled and bent so that it can screw to the Weber, using the threaded holes where the choke mechanism was located. The bracket along with the throttle disk linkage is shown in the photos below secured to the weber.
Once the bracket has been made and attached to the Weber along with the disk shaped linkage, the Weber can be bolted to the adaptor plate using the nuts and star washers that came with the adaptor plate. Its a downhill run from here, slotting the accelerator cable in the slot on the disk, and using the bracket to set the adjustment. Most Weber DGV's incorporate a fuel return line, just like the standard Nikki so hooking up the fuel lines is identical to how you removed them from the Nikki. In the instance of obtaining a Weber with only a fuel inlet, you can either block the return line off completely, use a brass tee-piece from after the fuel filter, one line going to the carby and one to the return line, or another option is buying a fuel filter with twin outlets such as Ryco part no. 9702??. As always, your fuel mixtures should be analysed by a dyno workshop with a wide band oxygen sensor. This is relatively cheap to the cost of either wasting fuel and power with a rich mixture, or wasting power and blowing motors with a lean mixture. Expect to pay around $50-$150 to get the carby checked, with possibly a change in jet sizes. The benefit of this is that you can also get a horsepower readout at the same time. Most likely, the jetting will be slightly rich for a 1600, as the 32/36 DGV is factory fitment on 2 litre engines. This can either be corrected by smaller main jets, or slightly larger air corrector jets. Smaller main jets is the better alternative, but they will have to be soldered up and re-drilled to the desired size.
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