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At one time I too have had limited success when it came to the carburettor and 4 stroke petrol engines. I made an Air-cooled version of Edgar T Westbury's Seagull engine, made the carburettor to his design and after many hours of adjustment, as described by ETW I eventually reached a stage where the engine would run reasonably well. This was I felt not good enough as the engine could I thoiught tick-over more slowly and pick up from idle to full throttle a lot better. Plus the plugs were always black indicating a rich mixture. I therefore decided to set about designing a new style carburettor for this engine. It follows the traditional barrel type throttle with an adjustable air bleed, but instead of the plain orifice across the jet as in ETW's design I added an adjustable airflow. I also designed the jet such that it was submerged, there being a small reservoir of petrol available for sudden demands. The aim of the design was to have a carburettor that would work "straight out of the box" and minimal fiddling. I fitted the carburettor to the Seagull and the engine was tuned and ticking over much slower than before all with-in 15 minutes. The engine would pick-up and accelerate to flat-out without the slightest hesitation, I did write the article up for Engineering in Miniature and it was published sometime back.If I could fathom out how to load photographs onto this system I would let you see how it was done.Gray,
Really nice work Graham! Dave