Robin Colbourne Posted October 9 Share Posted October 9 The ' least-liked engines' thread got me thinking about why we have o-rings on needle valves. The leaky o-ring seems to be the Achilles heel on so many engines, that I wonder why they are there and so widely adopted, given that engines seemed to work perfectly well before o-ring needles were introduced somewhere in the late 80s/early 90s. Was the cost of producing a needle and spray bar that doesn't leak without an o-ring prohibitively expensive or was it something else? 2 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 10 Share Posted October 10 I think we do tend to look back on some older engines wirh rose tinted specs. Todays engines generally have much larger choke area and consequently lower fuel suction so we pressurise the fuel supply using exhaust. This often resulted in a lot of fuel leaking out rather than air leaking in so "0" rings are used as a seal that work ...... most if the time. Remeber we often used a short piece of fuel tubing on the NV ? Also an "0" ring at the base of a carb or on a backplate is simple and effective way to make a seal. O rings should be available from engineering suppliers. Order using internal diameter and section thickness/diameter. Ive found many suppliers on ebay for the odd sizes I use when making stuff . Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted October 10 Share Posted October 10 Modelfixings supply a variety of O rings, some specifically for R/C carburettors. https://www.modelfixings.co.uk/o_rings.htm Quote Link to comment Share on other sites More sharing options...
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