dave.vitesse Posted July 24, 2018 Report Share Posted July 24, 2018 The ABM biased needles are for the later carbs and will not fit yours. The needles are BO, H6, BN. getting richer with each one. If you are happy the fuel pump is not the problem then due to the use of free flow air cleaners it would be worth trying H6 needles. If you let more air in you have to fit richer needles to compensate. Everything has to be kept in balance. As interest I have found that the standard stainless steel exhaust systems give less obstructive flow than the original types. There's less baffling in the boxes. Dave 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted July 24, 2018 Report Share Posted July 24, 2018 the simple answer is to fit a std air box and filters and needles and see if it does as triumph intended but there again youre not on std carbs the reasoning is few of us have a development deptment to record and log all the requirements to make the car do what it says on the tin as soon as you make changes without any idea where we're going you end up with a hotch potch hoping its better ....often an ongoing nightmare and all the fun ..as you have found ...............disappears Pete 1 Link to comment Share on other sites More sharing options...
dave.vitesse Posted July 24, 2018 Report Share Posted July 24, 2018 Very true Pete. Uncontrolled changes can end up in making thing much worse. Particularly with the engine breathing set-up. The use of H6 needles when you have free flow air filters came from development work carried out by SAH in the 1960's. So hopefully not a blind change. Dave Link to comment Share on other sites More sharing options...
citybreeze Posted July 24, 2018 Author Report Share Posted July 24, 2018 I haven't ruled out the fuel pump or restriction of fuel flow by the filters just yet, waiting for parts to arrive to swap in. I have the H6 needles already, so may go up to BN if the problem remains. I assumed the AUD257 carbs were standard as they were what was fitted when I bought the car. Which carbs should be on there? The exhaust on there does look to be stainless steel, but original pattern. So maybe it is one of the ones with less baffling. If I get chance at the weekend, I may put the standard airbox back on and see what happens. 1 Link to comment Share on other sites More sharing options...
Anglefire Posted July 24, 2018 Report Share Posted July 24, 2018 Dave, I know little about the various needles but have changed the graph to include H6, BN and BO 1 Link to comment Share on other sites More sharing options...
dave.vitesse Posted July 24, 2018 Report Share Posted July 24, 2018 AUD257 carbs were fitted to the UK Mk3 Spit. Dave Link to comment Share on other sites More sharing options...
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