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carby habbits

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  • carby habbits

    hey guys how are we allafew weeks, ago the carby, on the scooby do played up and , well, it got me tearing my hair out wondering why

  • #2
    Hi Adrian, you"ve opened a can of worms! Tuning carby"s is a dark art. From your description, the secondary jets are too large and the things to look for would be black exhaust and/or plugs. Generally Gyros engines tend to "breathe" better than when they were in cars because of the exhausts and mufflers we use, so there is an increase in the airflow. This results in more venturi effect across the jets and thus more fuel being sucked into the chamber giving a richer mixture. The vehicle which your weber came from obviously had a very different flow characteristic than your gyro and this is what is probably causing your symptoms.One of the other guys on the forum using a weber should be able to give you a guide on what numbers to use.


    • #3
      G"day Adrian. The Webber you are using has a vacuum operated secondary throat. The manifold Vacuum is an infinately variable amount, controlled by the throttle position. The problem is that the vacuum pot controlling the secondary is "seeing" the correct vacuum to open the throat and once it starts to open it is seeing more vacuum again as the revs come up, and pulling the throat wide open. There should in fact be less vacuum with the throat wide open so something else is creating a false vacuum reading.It can be something as simple as a faulty or incorrect carby gasket, but the most common cause is a restricted inlet (too small or blocked air filter, too small carby heat tube, or too small inlet aperture).The throttle response should be linear all the way, and not jump to full throttle. Hope this helps.


      • #4
        thanks guysit makes sense , i had my thoughs about the manifold, as the adaptor plate for the carby seem to block a portion of the inlet off, as in a restriction, but once its going it runs very well,im not sure about the jets, i worked out the litres per hour and it seem to use about 17 litres/hour maybe less so as its working like it is im happy, went for a fly around the lakes and coorong and getting use to the different throtle settings, i believe im up for another manifold sooner down the track, at preasent just trying to get some flying in while the weather is not badcheersadrian